diff --git a/CMakeLists.txt b/CMakeLists.txt
index 89f33e1418..d7487ce905 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -485,6 +485,7 @@ set(ZIG_STD_FILES
     "json.zig"
     "lazy_init.zig"
     "linked_list.zig"
+    "macho.zig"
     "math/acos.zig"
     "math/acosh.zig"
     "math/asin.zig"
diff --git a/src/analyze.cpp b/src/analyze.cpp
index 03cfa5b67b..d3a5c94aa1 100644
--- a/src/analyze.cpp
+++ b/src/analyze.cpp
@@ -19,12 +19,12 @@
 
 static const size_t default_backward_branch_quota = 1000;
 
-static void resolve_enum_type(CodeGen *g, TypeTableEntry *enum_type);
-static void resolve_struct_type(CodeGen *g, TypeTableEntry *struct_type);
+static Error resolve_enum_type(CodeGen *g, TypeTableEntry *enum_type);
+static Error resolve_struct_type(CodeGen *g, TypeTableEntry *struct_type);
 
-static void resolve_struct_zero_bits(CodeGen *g, TypeTableEntry *struct_type);
-static void resolve_enum_zero_bits(CodeGen *g, TypeTableEntry *enum_type);
-static void resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type);
+static Error ATTRIBUTE_MUST_USE resolve_struct_zero_bits(CodeGen *g, TypeTableEntry *struct_type);
+static Error ATTRIBUTE_MUST_USE resolve_enum_zero_bits(CodeGen *g, TypeTableEntry *enum_type);
+static Error ATTRIBUTE_MUST_USE resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type);
 static void analyze_fn_body(CodeGen *g, FnTableEntry *fn_table_entry);
 
 ErrorMsg *add_node_error(CodeGen *g, AstNode *node, Buf *msg) {
@@ -370,15 +370,20 @@ uint64_t type_size_bits(CodeGen *g, TypeTableEntry *type_entry) {
     return LLVMSizeOfTypeInBits(g->target_data_ref, type_entry->type_ref);
 }
 
-bool type_is_copyable(CodeGen *g, TypeTableEntry *type_entry) {
-    type_ensure_zero_bits_known(g, type_entry);
+Result<bool> type_is_copyable(CodeGen *g, TypeTableEntry *type_entry) {
+    Error err;
+    if ((err = type_ensure_zero_bits_known(g, type_entry)))
+        return err;
+
     if (!type_has_bits(type_entry))
         return true;
 
     if (!handle_is_ptr(type_entry))
         return true;
 
-    ensure_complete_type(g, type_entry);
+    if ((err = ensure_complete_type(g, type_entry)))
+        return err;
+
     return type_entry->is_copyable;
 }
 
@@ -447,7 +452,7 @@ TypeTableEntry *get_pointer_to_type_extra(CodeGen *g, TypeTableEntry *child_type
         }
     }
 
-    type_ensure_zero_bits_known(g, child_type);
+    assertNoError(type_ensure_zero_bits_known(g, child_type));
 
     TypeTableEntry *entry = new_type_table_entry(TypeTableEntryIdPointer);
     entry->is_copyable = true;
@@ -554,11 +559,11 @@ TypeTableEntry *get_optional_type(CodeGen *g, TypeTableEntry *child_type) {
         TypeTableEntry *entry = child_type->optional_parent;
         return entry;
     } else {
-        ensure_complete_type(g, child_type);
+        assertNoError(ensure_complete_type(g, child_type));
 
         TypeTableEntry *entry = new_type_table_entry(TypeTableEntryIdOptional);
         assert(child_type->type_ref || child_type->zero_bits);
-        entry->is_copyable = type_is_copyable(g, child_type);
+        entry->is_copyable = type_is_copyable(g, child_type).unwrap();
 
         buf_resize(&entry->name, 0);
         buf_appendf(&entry->name, "?%s", buf_ptr(&child_type->name));
@@ -650,7 +655,7 @@ TypeTableEntry *get_error_union_type(CodeGen *g, TypeTableEntry *err_set_type, T
     TypeTableEntry *entry = new_type_table_entry(TypeTableEntryIdErrorUnion);
     entry->is_copyable = true;
     assert(payload_type->di_type);
-    ensure_complete_type(g, payload_type);
+    assertNoError(ensure_complete_type(g, payload_type));
 
     buf_resize(&entry->name, 0);
     buf_appendf(&entry->name, "%s!%s", buf_ptr(&err_set_type->name), buf_ptr(&payload_type->name));
@@ -739,7 +744,7 @@ TypeTableEntry *get_array_type(CodeGen *g, TypeTableEntry *child_type, uint64_t
         return entry;
     }
 
-    ensure_complete_type(g, child_type);
+    assertNoError(ensure_complete_type(g, child_type));
 
     TypeTableEntry *entry = new_type_table_entry(TypeTableEntryIdArray);
     entry->zero_bits = (array_size == 0) || child_type->zero_bits;
@@ -1050,13 +1055,13 @@ TypeTableEntry *get_ptr_to_stack_trace_type(CodeGen *g) {
 }
 
 TypeTableEntry *get_fn_type(CodeGen *g, FnTypeId *fn_type_id) {
+    Error err;
     auto table_entry = g->fn_type_table.maybe_get(fn_type_id);
     if (table_entry) {
         return table_entry->value;
     }
     if (fn_type_id->return_type != nullptr) {
-        ensure_complete_type(g, fn_type_id->return_type);
-        if (type_is_invalid(fn_type_id->return_type))
+        if ((err = ensure_complete_type(g, fn_type_id->return_type)))
             return g->builtin_types.entry_invalid;
         assert(fn_type_id->return_type->id != TypeTableEntryIdOpaque);
     } else {
@@ -1172,8 +1177,7 @@ TypeTableEntry *get_fn_type(CodeGen *g, FnTypeId *fn_type_id) {
             gen_param_info->src_index = i;
             gen_param_info->gen_index = SIZE_MAX;
 
-            ensure_complete_type(g, type_entry);
-            if (type_is_invalid(type_entry))
+            if ((err = ensure_complete_type(g, type_entry)))
                 return g->builtin_types.entry_invalid;
 
             if (type_has_bits(type_entry)) {
@@ -1493,6 +1497,7 @@ TypeTableEntry *get_auto_err_set_type(CodeGen *g, FnTableEntry *fn_entry) {
 static TypeTableEntry *analyze_fn_type(CodeGen *g, AstNode *proto_node, Scope *child_scope, FnTableEntry *fn_entry) {
     assert(proto_node->type == NodeTypeFnProto);
     AstNodeFnProto *fn_proto = &proto_node->data.fn_proto;
+    Error err;
 
     FnTypeId fn_type_id = {0};
     init_fn_type_id(&fn_type_id, proto_node, proto_node->data.fn_proto.params.length);
@@ -1550,7 +1555,8 @@ static TypeTableEntry *analyze_fn_type(CodeGen *g, AstNode *proto_node, Scope *c
             return g->builtin_types.entry_invalid;
         }
         if (!calling_convention_allows_zig_types(fn_type_id.cc)) {
-            type_ensure_zero_bits_known(g, type_entry);
+            if ((err = type_ensure_zero_bits_known(g, type_entry)))
+                return g->builtin_types.entry_invalid;
             if (!type_has_bits(type_entry)) {
                 add_node_error(g, param_node->data.param_decl.type,
                     buf_sprintf("parameter of type '%s' has 0 bits; not allowed in function with calling convention '%s'",
@@ -1598,7 +1604,8 @@ static TypeTableEntry *analyze_fn_type(CodeGen *g, AstNode *proto_node, Scope *c
             case TypeTableEntryIdUnion:
             case TypeTableEntryIdFn:
             case TypeTableEntryIdPromise:
-                type_ensure_zero_bits_known(g, type_entry);
+                if ((err = type_ensure_zero_bits_known(g, type_entry)))
+                    return g->builtin_types.entry_invalid;
                 if (type_requires_comptime(type_entry)) {
                     add_node_error(g, param_node->data.param_decl.type,
                         buf_sprintf("parameter of type '%s' must be declared comptime",
@@ -1729,24 +1736,25 @@ bool type_is_invalid(TypeTableEntry *type_entry) {
 }
 
 
-static void resolve_enum_type(CodeGen *g, TypeTableEntry *enum_type) {
+static Error resolve_enum_type(CodeGen *g, TypeTableEntry *enum_type) {
     assert(enum_type->id == TypeTableEntryIdEnum);
 
     if (enum_type->data.enumeration.complete)
-        return;
+        return ErrorNone;
 
-    resolve_enum_zero_bits(g, enum_type);
-    if (type_is_invalid(enum_type))
-        return;
+    Error err;
+    if ((err = resolve_enum_zero_bits(g, enum_type)))
+        return err;
 
     AstNode *decl_node = enum_type->data.enumeration.decl_node;
 
     if (enum_type->data.enumeration.embedded_in_current) {
         if (!enum_type->data.enumeration.reported_infinite_err) {
+            enum_type->data.enumeration.is_invalid = true;
             enum_type->data.enumeration.reported_infinite_err = true;
             add_node_error(g, decl_node, buf_sprintf("enum '%s' contains itself", buf_ptr(&enum_type->name)));
         }
-        return;
+        return ErrorSemanticAnalyzeFail;
     }
 
     assert(!enum_type->data.enumeration.zero_bits_loop_flag);
@@ -1778,7 +1786,7 @@ static void resolve_enum_type(CodeGen *g, TypeTableEntry *enum_type) {
     enum_type->data.enumeration.complete = true;
 
     if (enum_type->data.enumeration.is_invalid)
-        return;
+        return ErrorSemanticAnalyzeFail;
 
     if (enum_type->zero_bits) {
         enum_type->type_ref = LLVMVoidType();
@@ -1797,7 +1805,7 @@ static void resolve_enum_type(CodeGen *g, TypeTableEntry *enum_type) {
 
         ZigLLVMReplaceTemporary(g->dbuilder, enum_type->di_type, replacement_di_type);
         enum_type->di_type = replacement_di_type;
-        return;
+        return ErrorNone;
     }
 
     TypeTableEntry *tag_int_type = enum_type->data.enumeration.tag_int_type;
@@ -1815,6 +1823,7 @@ static void resolve_enum_type(CodeGen *g, TypeTableEntry *enum_type) {
 
     ZigLLVMReplaceTemporary(g->dbuilder, enum_type->di_type, tag_di_type);
     enum_type->di_type = tag_di_type;
+    return ErrorNone;
 }
 
 
@@ -1897,15 +1906,15 @@ TypeTableEntry *get_struct_type(CodeGen *g, const char *type_name, const char *f
     return struct_type;
 }
 
-static void resolve_struct_type(CodeGen *g, TypeTableEntry *struct_type) {
+static Error resolve_struct_type(CodeGen *g, TypeTableEntry *struct_type) {
     assert(struct_type->id == TypeTableEntryIdStruct);
 
     if (struct_type->data.structure.complete)
-        return;
+        return ErrorNone;
 
-    resolve_struct_zero_bits(g, struct_type);
-    if (struct_type->data.structure.is_invalid)
-        return;
+    Error err;
+    if ((err = resolve_struct_zero_bits(g, struct_type)))
+        return err;
 
     AstNode *decl_node = struct_type->data.structure.decl_node;
 
@@ -1916,7 +1925,7 @@ static void resolve_struct_type(CodeGen *g, TypeTableEntry *struct_type) {
             add_node_error(g, decl_node,
                     buf_sprintf("struct '%s' contains itself", buf_ptr(&struct_type->name)));
         }
-        return;
+        return ErrorSemanticAnalyzeFail;
     }
 
     assert(!struct_type->data.structure.zero_bits_loop_flag);
@@ -1943,8 +1952,7 @@ static void resolve_struct_type(CodeGen *g, TypeTableEntry *struct_type) {
         TypeStructField *type_struct_field = &struct_type->data.structure.fields[i];
         TypeTableEntry *field_type = type_struct_field->type_entry;
 
-        ensure_complete_type(g, field_type);
-        if (type_is_invalid(field_type)) {
+        if ((err = ensure_complete_type(g, field_type))) {
             struct_type->data.structure.is_invalid = true;
             break;
         }
@@ -2026,7 +2034,7 @@ static void resolve_struct_type(CodeGen *g, TypeTableEntry *struct_type) {
     struct_type->data.structure.complete = true;
 
     if (struct_type->data.structure.is_invalid)
-        return;
+        return ErrorSemanticAnalyzeFail;
 
     if (struct_type->zero_bits) {
         struct_type->type_ref = LLVMVoidType();
@@ -2045,7 +2053,7 @@ static void resolve_struct_type(CodeGen *g, TypeTableEntry *struct_type) {
                 0, nullptr, di_element_types, (int)debug_field_count, 0, nullptr, "");
         ZigLLVMReplaceTemporary(g->dbuilder, struct_type->di_type, replacement_di_type);
         struct_type->di_type = replacement_di_type;
-        return;
+        return ErrorNone;
     }
     assert(struct_type->di_type);
 
@@ -2128,17 +2136,19 @@ static void resolve_struct_type(CodeGen *g, TypeTableEntry *struct_type) {
 
     ZigLLVMReplaceTemporary(g->dbuilder, struct_type->di_type, replacement_di_type);
     struct_type->di_type = replacement_di_type;
+
+    return ErrorNone;
 }
 
-static void resolve_union_type(CodeGen *g, TypeTableEntry *union_type) {
+static Error resolve_union_type(CodeGen *g, TypeTableEntry *union_type) {
     assert(union_type->id == TypeTableEntryIdUnion);
 
     if (union_type->data.unionation.complete)
-        return;
+        return ErrorNone;
 
-    resolve_union_zero_bits(g, union_type);
-    if (type_is_invalid(union_type))
-        return;
+    Error err;
+    if ((err = resolve_union_zero_bits(g, union_type)))
+        return err;
 
     AstNode *decl_node = union_type->data.unionation.decl_node;
 
@@ -2148,7 +2158,7 @@ static void resolve_union_type(CodeGen *g, TypeTableEntry *union_type) {
             union_type->data.unionation.is_invalid = true;
             add_node_error(g, decl_node, buf_sprintf("union '%s' contains itself", buf_ptr(&union_type->name)));
         }
-        return;
+        return ErrorSemanticAnalyzeFail;
     }
 
     assert(!union_type->data.unionation.zero_bits_loop_flag);
@@ -2179,8 +2189,7 @@ static void resolve_union_type(CodeGen *g, TypeTableEntry *union_type) {
         TypeUnionField *union_field = &union_type->data.unionation.fields[i];
         TypeTableEntry *field_type = union_field->type_entry;
 
-        ensure_complete_type(g, field_type);
-        if (type_is_invalid(field_type)) {
+        if ((err = ensure_complete_type(g, field_type))) {
             union_type->data.unionation.is_invalid = true;
             continue;
         }
@@ -2219,7 +2228,7 @@ static void resolve_union_type(CodeGen *g, TypeTableEntry *union_type) {
     union_type->data.unionation.most_aligned_union_member = most_aligned_union_member;
 
     if (union_type->data.unionation.is_invalid)
-        return;
+        return ErrorSemanticAnalyzeFail;
 
     if (union_type->zero_bits) {
         union_type->type_ref = LLVMVoidType();
@@ -2238,7 +2247,7 @@ static void resolve_union_type(CodeGen *g, TypeTableEntry *union_type) {
 
         ZigLLVMReplaceTemporary(g->dbuilder, union_type->di_type, replacement_di_type);
         union_type->di_type = replacement_di_type;
-        return;
+        return ErrorNone;
     }
 
     uint64_t padding_in_bits = biggest_size_in_bits - size_of_most_aligned_member_in_bits;
@@ -2274,7 +2283,7 @@ static void resolve_union_type(CodeGen *g, TypeTableEntry *union_type) {
 
         ZigLLVMReplaceTemporary(g->dbuilder, union_type->di_type, replacement_di_type);
         union_type->di_type = replacement_di_type;
-        return;
+        return ErrorNone;
     }
 
     LLVMTypeRef union_type_ref;
@@ -2293,7 +2302,7 @@ static void resolve_union_type(CodeGen *g, TypeTableEntry *union_type) {
 
         ZigLLVMReplaceTemporary(g->dbuilder, union_type->di_type, tag_type->di_type);
         union_type->di_type = tag_type->di_type;
-        return;
+        return ErrorNone;
     } else {
         union_type_ref = most_aligned_union_member->type_ref;
     }
@@ -2367,19 +2376,21 @@ static void resolve_union_type(CodeGen *g, TypeTableEntry *union_type) {
 
     ZigLLVMReplaceTemporary(g->dbuilder, union_type->di_type, replacement_di_type);
     union_type->di_type = replacement_di_type;
+
+    return ErrorNone;
 }
 
-static void resolve_enum_zero_bits(CodeGen *g, TypeTableEntry *enum_type) {
+static Error resolve_enum_zero_bits(CodeGen *g, TypeTableEntry *enum_type) {
     assert(enum_type->id == TypeTableEntryIdEnum);
 
     if (enum_type->data.enumeration.zero_bits_known)
-        return;
+        return ErrorNone;
 
     if (enum_type->data.enumeration.zero_bits_loop_flag) {
         add_node_error(g, enum_type->data.enumeration.decl_node,
             buf_sprintf("'%s' depends on itself", buf_ptr(&enum_type->name)));
         enum_type->data.enumeration.is_invalid = true;
-        return;
+        return ErrorSemanticAnalyzeFail;
     }
 
     enum_type->data.enumeration.zero_bits_loop_flag = true;
@@ -2398,7 +2409,7 @@ static void resolve_enum_zero_bits(CodeGen *g, TypeTableEntry *enum_type) {
         enum_type->data.enumeration.is_invalid = true;
         enum_type->data.enumeration.zero_bits_loop_flag = false;
         enum_type->data.enumeration.zero_bits_known = true;
-        return;
+        return ErrorSemanticAnalyzeFail;
     }
 
     enum_type->data.enumeration.src_field_count = field_count;
@@ -2525,13 +2536,18 @@ static void resolve_enum_zero_bits(CodeGen *g, TypeTableEntry *enum_type) {
     enum_type->data.enumeration.zero_bits_loop_flag = false;
     enum_type->zero_bits = !type_has_bits(tag_int_type);
     enum_type->data.enumeration.zero_bits_known = true;
+    assert(!enum_type->data.enumeration.is_invalid);
+
+    return ErrorNone;
 }
 
-static void resolve_struct_zero_bits(CodeGen *g, TypeTableEntry *struct_type) {
+static Error resolve_struct_zero_bits(CodeGen *g, TypeTableEntry *struct_type) {
     assert(struct_type->id == TypeTableEntryIdStruct);
 
+    Error err;
+
     if (struct_type->data.structure.zero_bits_known)
-        return;
+        return ErrorNone;
 
     if (struct_type->data.structure.zero_bits_loop_flag) {
         // If we get here it's due to recursion. This is a design flaw in the compiler,
@@ -2547,7 +2563,7 @@ static void resolve_struct_zero_bits(CodeGen *g, TypeTableEntry *struct_type) {
                 struct_type->data.structure.abi_alignment = LLVMABIAlignmentOfType(g->target_data_ref, LLVMPointerType(LLVMInt8Type(), 0));
             }
         }
-        return;
+        return ErrorNone;
     }
 
     struct_type->data.structure.zero_bits_loop_flag = true;
@@ -2596,8 +2612,7 @@ static void resolve_struct_zero_bits(CodeGen *g, TypeTableEntry *struct_type) {
                     buf_sprintf("enums, not structs, support field assignment"));
         }
 
-        type_ensure_zero_bits_known(g, field_type);
-        if (type_is_invalid(field_type)) {
+        if ((err = type_ensure_zero_bits_known(g, field_type))) {
             struct_type->data.structure.is_invalid = true;
             continue;
         }
@@ -2634,16 +2649,24 @@ static void resolve_struct_zero_bits(CodeGen *g, TypeTableEntry *struct_type) {
     struct_type->data.structure.gen_field_count = (uint32_t)gen_field_index;
     struct_type->zero_bits = (gen_field_index == 0);
     struct_type->data.structure.zero_bits_known = true;
+
+    if (struct_type->data.structure.is_invalid) {
+        return ErrorSemanticAnalyzeFail;
+    }
+
+    return ErrorNone;
 }
 
-static void resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type) {
+static Error resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type) {
     assert(union_type->id == TypeTableEntryIdUnion);
 
+    Error err;
+
     if (union_type->data.unionation.zero_bits_known)
-        return;
+        return ErrorNone;
 
     if (type_is_invalid(union_type))
-        return;
+        return ErrorSemanticAnalyzeFail;
 
     if (union_type->data.unionation.zero_bits_loop_flag) {
         // If we get here it's due to recursion. From this we conclude that the struct is
@@ -2660,7 +2683,7 @@ static void resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type) {
                         LLVMPointerType(LLVMInt8Type(), 0));
             }
         }
-        return;
+        return ErrorNone;
     }
 
     union_type->data.unionation.zero_bits_loop_flag = true;
@@ -2679,7 +2702,7 @@ static void resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type) {
         union_type->data.unionation.is_invalid = true;
         union_type->data.unionation.zero_bits_loop_flag = false;
         union_type->data.unionation.zero_bits_known = true;
-        return;
+        return ErrorSemanticAnalyzeFail;
     }
     union_type->data.unionation.src_field_count = field_count;
     union_type->data.unionation.fields = allocate<TypeUnionField>(field_count);
@@ -2711,13 +2734,13 @@ static void resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type) {
             tag_int_type = analyze_type_expr(g, scope, enum_type_node);
             if (type_is_invalid(tag_int_type)) {
                 union_type->data.unionation.is_invalid = true;
-                return;
+                return ErrorSemanticAnalyzeFail;
             }
             if (tag_int_type->id != TypeTableEntryIdInt) {
                 add_node_error(g, enum_type_node,
                     buf_sprintf("expected integer tag type, found '%s'", buf_ptr(&tag_int_type->name)));
                 union_type->data.unionation.is_invalid = true;
-                return;
+                return ErrorSemanticAnalyzeFail;
             }
         } else {
             tag_int_type = get_smallest_unsigned_int_type(g, field_count - 1);
@@ -2744,13 +2767,13 @@ static void resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type) {
         TypeTableEntry *enum_type = analyze_type_expr(g, scope, enum_type_node);
         if (type_is_invalid(enum_type)) {
             union_type->data.unionation.is_invalid = true;
-            return;
+            return ErrorSemanticAnalyzeFail;
         }
         if (enum_type->id != TypeTableEntryIdEnum) {
             union_type->data.unionation.is_invalid = true;
             add_node_error(g, enum_type_node,
                 buf_sprintf("expected enum tag type, found '%s'", buf_ptr(&enum_type->name)));
-            return;
+            return ErrorSemanticAnalyzeFail;
         }
         tag_type = enum_type;
         abi_alignment_so_far = get_abi_alignment(g, enum_type); // this populates src_field_count
@@ -2789,8 +2812,7 @@ static void resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type) {
             }
         } else {
             field_type = analyze_type_expr(g, scope, field_node->data.struct_field.type);
-            type_ensure_zero_bits_known(g, field_type);
-            if (type_is_invalid(field_type)) {
+            if ((err = type_ensure_zero_bits_known(g, field_type))) {
                 union_type->data.unionation.is_invalid = true;
                 continue;
             }
@@ -2883,7 +2905,7 @@ static void resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type) {
     union_type->data.unionation.abi_alignment = abi_alignment_so_far;
 
     if (union_type->data.unionation.is_invalid)
-        return;
+        return ErrorSemanticAnalyzeFail;
 
     bool src_have_tag = decl_node->data.container_decl.auto_enum ||
         decl_node->data.container_decl.init_arg_expr != nullptr;
@@ -2905,7 +2927,7 @@ static void resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type) {
         add_node_error(g, source_node,
             buf_sprintf("%s union does not support enum tag type", qual_str));
         union_type->data.unionation.is_invalid = true;
-        return;
+        return ErrorSemanticAnalyzeFail;
     }
 
     if (create_enum_type) {
@@ -2970,6 +2992,8 @@ static void resolve_union_zero_bits(CodeGen *g, TypeTableEntry *union_type) {
     union_type->data.unionation.gen_field_count = gen_field_index;
     union_type->zero_bits = (gen_field_index == 0 && (field_count < 2 || !src_have_tag));
     union_type->data.unionation.zero_bits_known = true;
+    assert(!union_type->data.unionation.is_invalid);
+    return ErrorNone;
 }
 
 static void get_fully_qualified_decl_name_internal(Buf *buf, Scope *scope, uint8_t sep) {
@@ -3463,13 +3487,13 @@ VariableTableEntry *add_variable(CodeGen *g, AstNode *source_node, Scope *parent
     variable_entry->shadowable = false;
     variable_entry->mem_slot_index = SIZE_MAX;
     variable_entry->src_arg_index = SIZE_MAX;
-    variable_entry->align_bytes = get_abi_alignment(g, value->type);
 
     assert(name);
-
     buf_init_from_buf(&variable_entry->name, name);
 
-    if (value->type->id != TypeTableEntryIdInvalid) {
+    if (!type_is_invalid(value->type)) {
+        variable_entry->align_bytes = get_abi_alignment(g, value->type);
+
         VariableTableEntry *existing_var = find_variable(g, parent_scope, name);
         if (existing_var && !existing_var->shadowable) {
             ErrorMsg *msg = add_node_error(g, source_node,
@@ -5311,13 +5335,13 @@ ConstExprValue *create_const_arg_tuple(CodeGen *g, size_t arg_index_start, size_
 
 
 void init_const_undefined(CodeGen *g, ConstExprValue *const_val) {
+    Error err;
     TypeTableEntry *wanted_type = const_val->type;
     if (wanted_type->id == TypeTableEntryIdArray) {
         const_val->special = ConstValSpecialStatic;
         const_val->data.x_array.special = ConstArraySpecialUndef;
     } else if (wanted_type->id == TypeTableEntryIdStruct) {
-        ensure_complete_type(g, wanted_type);
-        if (type_is_invalid(wanted_type)) {
+        if ((err = ensure_complete_type(g, wanted_type))) {
             return;
         }
 
@@ -5350,27 +5374,33 @@ ConstExprValue *create_const_vals(size_t count) {
     return vals;
 }
 
-void ensure_complete_type(CodeGen *g, TypeTableEntry *type_entry) {
+Error ensure_complete_type(CodeGen *g, TypeTableEntry *type_entry) {
+    if (type_is_invalid(type_entry))
+        return ErrorSemanticAnalyzeFail;
     if (type_entry->id == TypeTableEntryIdStruct) {
         if (!type_entry->data.structure.complete)
-            resolve_struct_type(g, type_entry);
+            return resolve_struct_type(g, type_entry);
     } else if (type_entry->id == TypeTableEntryIdEnum) {
         if (!type_entry->data.enumeration.complete)
-            resolve_enum_type(g, type_entry);
+            return resolve_enum_type(g, type_entry);
     } else if (type_entry->id == TypeTableEntryIdUnion) {
         if (!type_entry->data.unionation.complete)
-            resolve_union_type(g, type_entry);
+            return resolve_union_type(g, type_entry);
     }
+    return ErrorNone;
 }
 
-void type_ensure_zero_bits_known(CodeGen *g, TypeTableEntry *type_entry) {
+Error type_ensure_zero_bits_known(CodeGen *g, TypeTableEntry *type_entry) {
+    if (type_is_invalid(type_entry))
+        return ErrorSemanticAnalyzeFail;
     if (type_entry->id == TypeTableEntryIdStruct) {
-        resolve_struct_zero_bits(g, type_entry);
+        return resolve_struct_zero_bits(g, type_entry);
     } else if (type_entry->id == TypeTableEntryIdEnum) {
-        resolve_enum_zero_bits(g, type_entry);
+        return resolve_enum_zero_bits(g, type_entry);
     } else if (type_entry->id == TypeTableEntryIdUnion) {
-        resolve_union_zero_bits(g, type_entry);
+        return resolve_union_zero_bits(g, type_entry);
     }
+    return ErrorNone;
 }
 
 bool ir_get_var_is_comptime(VariableTableEntry *var) {
@@ -6213,7 +6243,7 @@ LinkLib *add_link_lib(CodeGen *g, Buf *name) {
 }
 
 uint32_t get_abi_alignment(CodeGen *g, TypeTableEntry *type_entry) {
-    type_ensure_zero_bits_known(g, type_entry);
+    assertNoError(type_ensure_zero_bits_known(g, type_entry));
     if (type_entry->zero_bits) return 0;
 
     // We need to make this function work without requiring ensure_complete_type
diff --git a/src/analyze.hpp b/src/analyze.hpp
index e4dfae4ecb..0b52e9a5e6 100644
--- a/src/analyze.hpp
+++ b/src/analyze.hpp
@@ -9,6 +9,7 @@
 #define ZIG_ANALYZE_HPP
 
 #include "all_types.hpp"
+#include "result.hpp"
 
 void semantic_analyze(CodeGen *g);
 ErrorMsg *add_node_error(CodeGen *g, AstNode *node, Buf *msg);
@@ -88,8 +89,8 @@ void init_fn_type_id(FnTypeId *fn_type_id, AstNode *proto_node, size_t param_cou
 AstNode *get_param_decl_node(FnTableEntry *fn_entry, size_t index);
 FnTableEntry *scope_get_fn_if_root(Scope *scope);
 bool type_requires_comptime(TypeTableEntry *type_entry);
-void ensure_complete_type(CodeGen *g, TypeTableEntry *type_entry);
-void type_ensure_zero_bits_known(CodeGen *g, TypeTableEntry *type_entry);
+Error ATTRIBUTE_MUST_USE ensure_complete_type(CodeGen *g, TypeTableEntry *type_entry);
+Error ATTRIBUTE_MUST_USE type_ensure_zero_bits_known(CodeGen *g, TypeTableEntry *type_entry);
 void complete_enum(CodeGen *g, TypeTableEntry *enum_type);
 bool ir_get_var_is_comptime(VariableTableEntry *var);
 bool const_values_equal(ConstExprValue *a, ConstExprValue *b);
@@ -178,7 +179,7 @@ TypeTableEntryId type_id_at_index(size_t index);
 size_t type_id_len();
 size_t type_id_index(TypeTableEntry *entry);
 TypeTableEntry *get_generic_fn_type(CodeGen *g, FnTypeId *fn_type_id);
-bool type_is_copyable(CodeGen *g, TypeTableEntry *type_entry);
+Result<bool> type_is_copyable(CodeGen *g, TypeTableEntry *type_entry);
 LinkLib *create_link_lib(Buf *name);
 bool calling_convention_does_first_arg_return(CallingConvention cc);
 LinkLib *add_link_lib(CodeGen *codegen, Buf *lib);
diff --git a/src/ir.cpp b/src/ir.cpp
index 6ee44b507d..d23968d0c4 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -8711,6 +8711,7 @@ static void update_errors_helper(CodeGen *g, ErrorTableEntry ***errors, size_t *
 }
 
 static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_node, TypeTableEntry *expected_type, IrInstruction **instructions, size_t instruction_count) {
+    Error err;
     assert(instruction_count >= 1);
     IrInstruction *prev_inst = instructions[0];
     if (type_is_invalid(prev_inst->value.type)) {
@@ -9172,8 +9173,7 @@ static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_nod
         if (prev_type->id == TypeTableEntryIdEnum && cur_type->id == TypeTableEntryIdUnion &&
             (cur_type->data.unionation.decl_node->data.container_decl.auto_enum || cur_type->data.unionation.decl_node->data.container_decl.init_arg_expr != nullptr))
         {
-            type_ensure_zero_bits_known(ira->codegen, cur_type);
-            if (type_is_invalid(cur_type))
+            if ((err = type_ensure_zero_bits_known(ira->codegen, cur_type)))
                 return ira->codegen->builtin_types.entry_invalid;
             if (cur_type->data.unionation.tag_type == prev_type) {
                 continue;
@@ -9183,8 +9183,7 @@ static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_nod
         if (cur_type->id == TypeTableEntryIdEnum && prev_type->id == TypeTableEntryIdUnion &&
             (prev_type->data.unionation.decl_node->data.container_decl.auto_enum || prev_type->data.unionation.decl_node->data.container_decl.init_arg_expr != nullptr))
         {
-            type_ensure_zero_bits_known(ira->codegen, prev_type);
-            if (type_is_invalid(prev_type))
+            if ((err = type_ensure_zero_bits_known(ira->codegen, prev_type)))
                 return ira->codegen->builtin_types.entry_invalid;
             if (prev_type->data.unionation.tag_type == cur_type) {
                 prev_inst = cur_inst;
@@ -9999,11 +9998,11 @@ static IrInstruction *ir_analyze_array_to_slice(IrAnalyze *ira, IrInstruction *s
 static IrInstruction *ir_analyze_enum_to_int(IrAnalyze *ira, IrInstruction *source_instr,
         IrInstruction *target, TypeTableEntry *wanted_type)
 {
+    Error err;
     assert(wanted_type->id == TypeTableEntryIdInt);
 
     TypeTableEntry *actual_type = target->value.type;
-    ensure_complete_type(ira->codegen, actual_type);
-    if (type_is_invalid(actual_type))
+    if ((err = ensure_complete_type(ira->codegen, actual_type)))
         return ira->codegen->invalid_instruction;
 
     if (wanted_type != actual_type->data.enumeration.tag_int_type) {
@@ -10069,6 +10068,7 @@ static IrInstruction *ir_analyze_undefined_to_anything(IrAnalyze *ira, IrInstruc
 static IrInstruction *ir_analyze_enum_to_union(IrAnalyze *ira, IrInstruction *source_instr,
         IrInstruction *target, TypeTableEntry *wanted_type)
 {
+    Error err;
     assert(wanted_type->id == TypeTableEntryIdUnion);
     assert(target->value.type->id == TypeTableEntryIdEnum);
 
@@ -10078,8 +10078,7 @@ static IrInstruction *ir_analyze_enum_to_union(IrAnalyze *ira, IrInstruction *so
             return ira->codegen->invalid_instruction;
         TypeUnionField *union_field = find_union_field_by_tag(wanted_type, &val->data.x_enum_tag);
         assert(union_field != nullptr);
-        type_ensure_zero_bits_known(ira->codegen, union_field->type_entry);
-        if (type_is_invalid(union_field->type_entry))
+        if ((err = type_ensure_zero_bits_known(ira->codegen, union_field->type_entry)))
             return ira->codegen->invalid_instruction;
         if (!union_field->type_entry->zero_bits) {
             AstNode *field_node = wanted_type->data.unionation.decl_node->data.container_decl.fields.at(
@@ -10169,12 +10168,12 @@ static IrInstruction *ir_analyze_widen_or_shorten(IrAnalyze *ira, IrInstruction
 static IrInstruction *ir_analyze_int_to_enum(IrAnalyze *ira, IrInstruction *source_instr,
         IrInstruction *target, TypeTableEntry *wanted_type)
 {
+    Error err;
     assert(wanted_type->id == TypeTableEntryIdEnum);
 
     TypeTableEntry *actual_type = target->value.type;
 
-    ensure_complete_type(ira->codegen, wanted_type);
-    if (type_is_invalid(wanted_type))
+    if ((err = ensure_complete_type(ira->codegen, wanted_type)))
         return ira->codegen->invalid_instruction;
 
     if (actual_type != wanted_type->data.enumeration.tag_int_type) {
@@ -10517,6 +10516,7 @@ static void report_recursive_error(IrAnalyze *ira, AstNode *source_node, ConstCa
 static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_instr,
     TypeTableEntry *wanted_type, IrInstruction *value)
 {
+    Error err;
     TypeTableEntry *actual_type = value->value.type;
     AstNode *source_node = source_instr->source_node;
 
@@ -10796,8 +10796,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
     if (actual_type->id == TypeTableEntryIdComptimeFloat ||
         actual_type->id == TypeTableEntryIdComptimeInt)
     {
-        ensure_complete_type(ira->codegen, wanted_type);
-        if (type_is_invalid(wanted_type))
+        if ((err = ensure_complete_type(ira->codegen, wanted_type)))
             return ira->codegen->invalid_instruction;
         if (wanted_type->id == TypeTableEntryIdEnum) {
             IrInstruction *cast1 = ir_analyze_cast(ira, source_instr, wanted_type->data.enumeration.tag_int_type, value);
@@ -10853,8 +10852,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
 
     // cast from union to the enum type of the union
     if (actual_type->id == TypeTableEntryIdUnion && wanted_type->id == TypeTableEntryIdEnum) {
-        type_ensure_zero_bits_known(ira->codegen, actual_type);
-        if (type_is_invalid(actual_type))
+        if ((err = type_ensure_zero_bits_known(ira->codegen, actual_type)))
             return ira->codegen->invalid_instruction;
 
         if (actual_type->data.unionation.tag_type == wanted_type) {
@@ -10867,7 +10865,9 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
         (wanted_type->data.unionation.decl_node->data.container_decl.auto_enum ||
         wanted_type->data.unionation.decl_node->data.container_decl.init_arg_expr != nullptr))
     {
-        type_ensure_zero_bits_known(ira->codegen, wanted_type);
+        if ((err = type_ensure_zero_bits_known(ira->codegen, wanted_type)))
+            return ira->codegen->invalid_instruction;
+
         if (wanted_type->data.unionation.tag_type == actual_type) {
             return ir_analyze_enum_to_union(ira, source_instr, value, wanted_type);
         }
@@ -10879,7 +10879,9 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
         if (union_type->data.unionation.decl_node->data.container_decl.auto_enum ||
             union_type->data.unionation.decl_node->data.container_decl.init_arg_expr != nullptr)
         {
-            type_ensure_zero_bits_known(ira->codegen, union_type);
+            if ((err = type_ensure_zero_bits_known(ira->codegen, union_type)))
+                return ira->codegen->invalid_instruction;
+
             if (union_type->data.unionation.tag_type == actual_type) {
                 IrInstruction *cast1 = ir_analyze_cast(ira, source_instr, union_type, value);
                 if (type_is_invalid(cast1->value.type))
@@ -10923,8 +10925,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
         types_match_const_cast_only(ira, wanted_type->data.pointer.child_type,
             actual_type, source_node, !wanted_type->data.pointer.is_const).id == ConstCastResultIdOk)
     {
-        type_ensure_zero_bits_known(ira->codegen, actual_type);
-        if (type_is_invalid(actual_type)) {
+        if ((err = type_ensure_zero_bits_known(ira->codegen, actual_type))) {
             return ira->codegen->invalid_instruction;
         }
         if (!type_has_bits(actual_type)) {
@@ -11323,6 +11324,7 @@ static bool optional_value_is_null(ConstExprValue *val) {
 }
 
 static TypeTableEntry *ir_analyze_bin_op_cmp(IrAnalyze *ira, IrInstructionBinOp *bin_op_instruction) {
+    Error err;
     IrInstruction *op1 = bin_op_instruction->op1->other;
     IrInstruction *op2 = bin_op_instruction->op2->other;
     AstNode *source_node = bin_op_instruction->base.source_node;
@@ -11458,8 +11460,7 @@ static TypeTableEntry *ir_analyze_bin_op_cmp(IrAnalyze *ira, IrInstructionBinOp
     TypeTableEntry *resolved_type = ir_resolve_peer_types(ira, source_node, nullptr, instructions, 2);
     if (type_is_invalid(resolved_type))
         return resolved_type;
-    type_ensure_zero_bits_known(ira->codegen, resolved_type);
-    if (type_is_invalid(resolved_type))
+    if ((err = type_ensure_zero_bits_known(ira->codegen, resolved_type)))
         return resolved_type;
 
     bool operator_allowed;
@@ -12406,6 +12407,7 @@ static TypeTableEntry *ir_analyze_instruction_bin_op(IrAnalyze *ira, IrInstructi
 }
 
 static TypeTableEntry *ir_analyze_instruction_decl_var(IrAnalyze *ira, IrInstructionDeclVar *decl_var_instruction) {
+    Error err;
     VariableTableEntry *var = decl_var_instruction->var;
 
     IrInstruction *init_value = decl_var_instruction->init_value->other;
@@ -12439,8 +12441,7 @@ static TypeTableEntry *ir_analyze_instruction_decl_var(IrAnalyze *ira, IrInstruc
     if (type_is_invalid(result_type)) {
         result_type = ira->codegen->builtin_types.entry_invalid;
     } else {
-        type_ensure_zero_bits_known(ira->codegen, result_type);
-        if (type_is_invalid(result_type)) {
+        if ((err = type_ensure_zero_bits_known(ira->codegen, result_type))) {
             result_type = ira->codegen->builtin_types.entry_invalid;
         }
     }
@@ -12958,6 +12959,7 @@ static VariableTableEntry *get_fn_var_by_index(FnTableEntry *fn_entry, size_t in
 static IrInstruction *ir_get_var_ptr(IrAnalyze *ira, IrInstruction *instruction,
         VariableTableEntry *var)
 {
+    Error err;
     if (var->mem_slot_index != SIZE_MAX && var->owner_exec->analysis == nullptr) {
         assert(ira->codegen->errors.length != 0);
         return ira->codegen->invalid_instruction;
@@ -13012,7 +13014,8 @@ no_mem_slot:
             instruction->scope, instruction->source_node, var);
     var_ptr_instruction->value.type = get_pointer_to_type_extra(ira->codegen, var->value->type,
             var->src_is_const, is_volatile, PtrLenSingle, var->align_bytes, 0, 0);
-    type_ensure_zero_bits_known(ira->codegen, var->value->type);
+    if ((err = type_ensure_zero_bits_known(ira->codegen, var->value->type)))
+        return ira->codegen->invalid_instruction;
 
     bool in_fn_scope = (scope_fn_entry(var->parent_scope) != nullptr);
     var_ptr_instruction->value.data.rh_ptr = in_fn_scope ? RuntimeHintPtrStack : RuntimeHintPtrNonStack;
@@ -13024,6 +13027,7 @@ static TypeTableEntry *ir_analyze_fn_call(IrAnalyze *ira, IrInstructionCall *cal
     FnTableEntry *fn_entry, TypeTableEntry *fn_type, IrInstruction *fn_ref,
     IrInstruction *first_arg_ptr, bool comptime_fn_call, FnInline fn_inline)
 {
+    Error err;
     FnTypeId *fn_type_id = &fn_type->data.fn.fn_type_id;
     size_t first_arg_1_or_0 = first_arg_ptr ? 1 : 0;
 
@@ -13388,8 +13392,7 @@ static TypeTableEntry *ir_analyze_fn_call(IrAnalyze *ira, IrInstructionCall *cal
                 inst_fn_type_id.return_type = specified_return_type;
             }
 
-            type_ensure_zero_bits_known(ira->codegen, specified_return_type);
-            if (type_is_invalid(specified_return_type))
+            if ((err = type_ensure_zero_bits_known(ira->codegen, specified_return_type)))
                 return ira->codegen->builtin_types.entry_invalid;
 
             if (type_requires_comptime(specified_return_type)) {
@@ -13664,12 +13667,12 @@ static TypeTableEntry *ir_analyze_dereference(IrAnalyze *ira, IrInstructionUnOp
 }
 
 static TypeTableEntry *ir_analyze_maybe(IrAnalyze *ira, IrInstructionUnOp *un_op_instruction) {
+    Error err;
     IrInstruction *value = un_op_instruction->value->other;
     TypeTableEntry *type_entry = ir_resolve_type(ira, value);
     if (type_is_invalid(type_entry))
         return ira->codegen->builtin_types.entry_invalid;
-    ensure_complete_type(ira->codegen, type_entry);
-    if (type_is_invalid(type_entry))
+    if ((err = ensure_complete_type(ira->codegen, type_entry)))
         return ira->codegen->builtin_types.entry_invalid;
 
     switch (type_entry->id) {
@@ -14023,6 +14026,7 @@ static TypeTableEntry *adjust_ptr_len(CodeGen *g, TypeTableEntry *ptr_type, PtrL
 }
 
 static TypeTableEntry *ir_analyze_instruction_elem_ptr(IrAnalyze *ira, IrInstructionElemPtr *elem_ptr_instruction) {
+    Error err;
     IrInstruction *array_ptr = elem_ptr_instruction->array_ptr->other;
     if (type_is_invalid(array_ptr->value.type))
         return ira->codegen->builtin_types.entry_invalid;
@@ -14131,8 +14135,7 @@ static TypeTableEntry *ir_analyze_instruction_elem_ptr(IrAnalyze *ira, IrInstruc
         return ira->codegen->builtin_types.entry_invalid;
 
     bool safety_check_on = elem_ptr_instruction->safety_check_on;
-    ensure_complete_type(ira->codegen, return_type->data.pointer.child_type);
-    if (type_is_invalid(return_type->data.pointer.child_type))
+    if ((err = ensure_complete_type(ira->codegen, return_type->data.pointer.child_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     uint64_t elem_size = type_size(ira->codegen, return_type->data.pointer.child_type);
@@ -14352,9 +14355,10 @@ static IrInstruction *ir_analyze_container_member_access_inner(IrAnalyze *ira,
 static IrInstruction *ir_analyze_container_field_ptr(IrAnalyze *ira, Buf *field_name,
     IrInstruction *source_instr, IrInstruction *container_ptr, TypeTableEntry *container_type)
 {
+    Error err;
+
     TypeTableEntry *bare_type = container_ref_type(container_type);
-    ensure_complete_type(ira->codegen, bare_type);
-    if (type_is_invalid(bare_type))
+    if ((err = ensure_complete_type(ira->codegen, bare_type)))
         return ira->codegen->invalid_instruction;
 
     assert(container_ptr->value.type->id == TypeTableEntryIdPointer);
@@ -14553,6 +14557,7 @@ static ErrorTableEntry *find_err_table_entry(TypeTableEntry *err_set_type, Buf *
 }
 
 static TypeTableEntry *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstructionFieldPtr *field_ptr_instruction) {
+    Error err;
     IrInstruction *container_ptr = field_ptr_instruction->container_ptr->other;
     if (type_is_invalid(container_ptr->value.type))
         return ira->codegen->builtin_types.entry_invalid;
@@ -14654,8 +14659,7 @@ static TypeTableEntry *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstru
                     ConstPtrMutComptimeConst, ptr_is_const, ptr_is_volatile);
             }
             if (child_type->id == TypeTableEntryIdEnum) {
-                ensure_complete_type(ira->codegen, child_type);
-                if (type_is_invalid(child_type))
+                if ((err = ensure_complete_type(ira->codegen, child_type)))
                     return ira->codegen->builtin_types.entry_invalid;
 
                 TypeEnumField *field = find_enum_type_field(child_type, field_name);
@@ -14679,8 +14683,7 @@ static TypeTableEntry *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstru
                     (child_type->data.unionation.decl_node->data.container_decl.init_arg_expr != nullptr ||
                     child_type->data.unionation.decl_node->data.container_decl.auto_enum))
             {
-                ensure_complete_type(ira->codegen, child_type);
-                if (type_is_invalid(child_type))
+                if ((err = ensure_complete_type(ira->codegen, child_type)))
                     return ira->codegen->builtin_types.entry_invalid;
                 TypeUnionField *field = find_union_type_field(child_type, field_name);
                 if (field) {
@@ -15257,6 +15260,7 @@ static TypeTableEntry *ir_analyze_instruction_set_float_mode(IrAnalyze *ira,
 static TypeTableEntry *ir_analyze_instruction_slice_type(IrAnalyze *ira,
         IrInstructionSliceType *slice_type_instruction)
 {
+    Error err;
     uint32_t align_bytes;
     if (slice_type_instruction->align_value != nullptr) {
         if (!ir_resolve_align(ira, slice_type_instruction->align_value->other, &align_bytes))
@@ -15306,7 +15310,8 @@ static TypeTableEntry *ir_analyze_instruction_slice_type(IrAnalyze *ira,
         case TypeTableEntryIdBoundFn:
         case TypeTableEntryIdPromise:
             {
-                type_ensure_zero_bits_known(ira->codegen, child_type);
+                if ((err = type_ensure_zero_bits_known(ira->codegen, child_type)))
+                    return ira->codegen->builtin_types.entry_invalid;
                 TypeTableEntry *slice_ptr_type = get_pointer_to_type_extra(ira->codegen, child_type,
                         is_const, is_volatile, PtrLenUnknown, align_bytes, 0, 0);
                 TypeTableEntry *result_type = get_slice_type(ira->codegen, slice_ptr_type);
@@ -15444,11 +15449,11 @@ static TypeTableEntry *ir_analyze_instruction_promise_type(IrAnalyze *ira, IrIns
 static TypeTableEntry *ir_analyze_instruction_size_of(IrAnalyze *ira,
         IrInstructionSizeOf *size_of_instruction)
 {
+    Error err;
     IrInstruction *type_value = size_of_instruction->type_value->other;
     TypeTableEntry *type_entry = ir_resolve_type(ira, type_value);
 
-    ensure_complete_type(ira->codegen, type_entry);
-    if (type_is_invalid(type_entry))
+    if ((err = ensure_complete_type(ira->codegen, type_entry)))
         return ira->codegen->builtin_types.entry_invalid;
 
     switch (type_entry->id) {
@@ -15819,6 +15824,7 @@ static TypeTableEntry *ir_analyze_instruction_switch_br(IrAnalyze *ira,
 static TypeTableEntry *ir_analyze_instruction_switch_target(IrAnalyze *ira,
         IrInstructionSwitchTarget *switch_target_instruction)
 {
+    Error err;
     IrInstruction *target_value_ptr = switch_target_instruction->target_value_ptr->other;
     if (type_is_invalid(target_value_ptr->value.type))
         return ira->codegen->builtin_types.entry_invalid;
@@ -15845,8 +15851,7 @@ static TypeTableEntry *ir_analyze_instruction_switch_target(IrAnalyze *ira,
         if (pointee_val->special == ConstValSpecialRuntime)
             pointee_val = nullptr;
     }
-    ensure_complete_type(ira->codegen, target_type);
-    if (type_is_invalid(target_type))
+    if ((err = ensure_complete_type(ira->codegen, target_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     switch (target_type->id) {
@@ -15910,8 +15915,7 @@ static TypeTableEntry *ir_analyze_instruction_switch_target(IrAnalyze *ira,
             return tag_type;
         }
         case TypeTableEntryIdEnum: {
-            type_ensure_zero_bits_known(ira->codegen, target_type);
-            if (type_is_invalid(target_type))
+            if ((err = type_ensure_zero_bits_known(ira->codegen, target_type)))
                 return ira->codegen->builtin_types.entry_invalid;
             if (target_type->data.enumeration.src_field_count < 2) {
                 TypeEnumField *only_field = &target_type->data.enumeration.fields[0];
@@ -16113,10 +16117,10 @@ static TypeTableEntry *ir_analyze_instruction_ref(IrAnalyze *ira, IrInstructionR
 static TypeTableEntry *ir_analyze_container_init_fields_union(IrAnalyze *ira, IrInstruction *instruction,
     TypeTableEntry *container_type, size_t instr_field_count, IrInstructionContainerInitFieldsField *fields)
 {
+    Error err;
     assert(container_type->id == TypeTableEntryIdUnion);
 
-    ensure_complete_type(ira->codegen, container_type);
-    if (type_is_invalid(container_type))
+    if ((err = ensure_complete_type(ira->codegen, container_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     if (instr_field_count != 1) {
@@ -16145,8 +16149,7 @@ static TypeTableEntry *ir_analyze_container_init_fields_union(IrAnalyze *ira, Ir
     if (casted_field_value == ira->codegen->invalid_instruction)
         return ira->codegen->builtin_types.entry_invalid;
 
-    type_ensure_zero_bits_known(ira->codegen, casted_field_value->value.type);
-    if (type_is_invalid(casted_field_value->value.type))
+    if ((err = type_ensure_zero_bits_known(ira->codegen, casted_field_value->value.type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     bool is_comptime = ir_should_inline(ira->new_irb.exec, instruction->scope);
@@ -16180,6 +16183,7 @@ static TypeTableEntry *ir_analyze_container_init_fields_union(IrAnalyze *ira, Ir
 static TypeTableEntry *ir_analyze_container_init_fields(IrAnalyze *ira, IrInstruction *instruction,
     TypeTableEntry *container_type, size_t instr_field_count, IrInstructionContainerInitFieldsField *fields)
 {
+    Error err;
     if (container_type->id == TypeTableEntryIdUnion) {
         return ir_analyze_container_init_fields_union(ira, instruction, container_type, instr_field_count, fields);
     }
@@ -16190,8 +16194,7 @@ static TypeTableEntry *ir_analyze_container_init_fields(IrAnalyze *ira, IrInstru
         return ira->codegen->builtin_types.entry_invalid;
     }
 
-    ensure_complete_type(ira->codegen, container_type);
-    if (type_is_invalid(container_type))
+    if ((err = ensure_complete_type(ira->codegen, container_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     size_t actual_field_count = container_type->data.structure.src_field_count;
@@ -16572,6 +16575,7 @@ static TypeTableEntry *ir_analyze_instruction_err_name(IrAnalyze *ira, IrInstruc
 }
 
 static TypeTableEntry *ir_analyze_instruction_enum_tag_name(IrAnalyze *ira, IrInstructionTagName *instruction) {
+    Error err;
     IrInstruction *target = instruction->target->other;
     if (type_is_invalid(target->value.type))
         return ira->codegen->builtin_types.entry_invalid;
@@ -16579,8 +16583,7 @@ static TypeTableEntry *ir_analyze_instruction_enum_tag_name(IrAnalyze *ira, IrIn
     assert(target->value.type->id == TypeTableEntryIdEnum);
 
     if (instr_is_comptime(target)) {
-        type_ensure_zero_bits_known(ira->codegen, target->value.type);
-        if (type_is_invalid(target->value.type))
+        if ((err = type_ensure_zero_bits_known(ira->codegen, target->value.type)))
             return ira->codegen->builtin_types.entry_invalid;
         TypeEnumField *field = find_enum_field_by_tag(target->value.type, &target->value.data.x_bigint);
         ConstExprValue *array_val = create_const_str_lit(ira->codegen, field->name);
@@ -16604,6 +16607,7 @@ static TypeTableEntry *ir_analyze_instruction_enum_tag_name(IrAnalyze *ira, IrIn
 static TypeTableEntry *ir_analyze_instruction_field_parent_ptr(IrAnalyze *ira,
         IrInstructionFieldParentPtr *instruction)
 {
+    Error err;
     IrInstruction *type_value = instruction->type_value->other;
     TypeTableEntry *container_type = ir_resolve_type(ira, type_value);
     if (type_is_invalid(container_type))
@@ -16624,8 +16628,7 @@ static TypeTableEntry *ir_analyze_instruction_field_parent_ptr(IrAnalyze *ira,
         return ira->codegen->builtin_types.entry_invalid;
     }
 
-    ensure_complete_type(ira->codegen, container_type);
-    if (type_is_invalid(container_type))
+    if ((err = ensure_complete_type(ira->codegen, container_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     TypeStructField *field = find_struct_type_field(container_type, field_name);
@@ -16697,13 +16700,13 @@ static TypeTableEntry *ir_analyze_instruction_field_parent_ptr(IrAnalyze *ira,
 static TypeTableEntry *ir_analyze_instruction_offset_of(IrAnalyze *ira,
         IrInstructionOffsetOf *instruction)
 {
+    Error err;
     IrInstruction *type_value = instruction->type_value->other;
     TypeTableEntry *container_type = ir_resolve_type(ira, type_value);
     if (type_is_invalid(container_type))
         return ira->codegen->builtin_types.entry_invalid;
 
-    ensure_complete_type(ira->codegen, container_type);
-    if (type_is_invalid(container_type))
+    if ((err = ensure_complete_type(ira->codegen, container_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     IrInstruction *field_name_value = instruction->field_name->other;
@@ -16750,6 +16753,7 @@ static void ensure_field_index(TypeTableEntry *type, const char *field_name, siz
 
 static TypeTableEntry *ir_type_info_get_type(IrAnalyze *ira, const char *type_name, TypeTableEntry *root = nullptr)
 {
+    Error err;
     static ConstExprValue *type_info_var = nullptr;
     static TypeTableEntry *type_info_type = nullptr;
     if (type_info_var == nullptr)
@@ -16757,8 +16761,7 @@ static TypeTableEntry *ir_type_info_get_type(IrAnalyze *ira, const char *type_na
         type_info_var = get_builtin_value(ira->codegen, "TypeInfo");
         assert(type_info_var->type->id == TypeTableEntryIdMetaType);
 
-        ensure_complete_type(ira->codegen, type_info_var->data.x_type);
-        if (type_is_invalid(type_info_var->data.x_type))
+        if ((err = ensure_complete_type(ira->codegen, type_info_var->data.x_type)))
             return ira->codegen->builtin_types.entry_invalid;
 
         type_info_type = type_info_var->data.x_type;
@@ -16785,8 +16788,7 @@ static TypeTableEntry *ir_type_info_get_type(IrAnalyze *ira, const char *type_na
 
     VariableTableEntry *var = tld->var;
 
-    ensure_complete_type(ira->codegen, var->value->type);
-    if (type_is_invalid(var->value->type))
+    if ((err = ensure_complete_type(ira->codegen, var->value->type)))
         return ira->codegen->builtin_types.entry_invalid;
     assert(var->value->type->id == TypeTableEntryIdMetaType);
     return var->value->data.x_type;
@@ -16794,9 +16796,9 @@ static TypeTableEntry *ir_type_info_get_type(IrAnalyze *ira, const char *type_na
 
 static bool ir_make_type_info_defs(IrAnalyze *ira, ConstExprValue *out_val, ScopeDecls *decls_scope)
 {
+    Error err;
     TypeTableEntry *type_info_definition_type = ir_type_info_get_type(ira, "Definition");
-    ensure_complete_type(ira->codegen, type_info_definition_type);
-    if (type_is_invalid(type_info_definition_type))
+    if ((err = ensure_complete_type(ira->codegen, type_info_definition_type)))
         return false;
 
     ensure_field_index(type_info_definition_type, "name", 0);
@@ -16804,18 +16806,15 @@ static bool ir_make_type_info_defs(IrAnalyze *ira, ConstExprValue *out_val, Scop
     ensure_field_index(type_info_definition_type, "data", 2);
 
     TypeTableEntry *type_info_definition_data_type = ir_type_info_get_type(ira, "Data", type_info_definition_type);
-    ensure_complete_type(ira->codegen, type_info_definition_data_type);
-    if (type_is_invalid(type_info_definition_data_type))
+    if ((err = ensure_complete_type(ira->codegen, type_info_definition_data_type)))
         return false;
 
     TypeTableEntry *type_info_fn_def_type = ir_type_info_get_type(ira, "FnDef", type_info_definition_data_type);
-    ensure_complete_type(ira->codegen, type_info_fn_def_type);
-    if (type_is_invalid(type_info_fn_def_type))
+    if ((err = ensure_complete_type(ira->codegen, type_info_fn_def_type)))
         return false;
 
     TypeTableEntry *type_info_fn_def_inline_type = ir_type_info_get_type(ira, "Inline", type_info_fn_def_type);
-    ensure_complete_type(ira->codegen, type_info_fn_def_inline_type);
-    if (type_is_invalid(type_info_fn_def_inline_type))
+    if ((err = ensure_complete_type(ira->codegen, type_info_fn_def_inline_type)))
         return false;
 
     // Loop through our definitions once to figure out how many definitions we will generate info for.
@@ -16895,8 +16894,7 @@ static bool ir_make_type_info_defs(IrAnalyze *ira, ConstExprValue *out_val, Scop
             case TldIdVar:
                 {
                     VariableTableEntry *var = ((TldVar *)curr_entry->value)->var;
-                    ensure_complete_type(ira->codegen, var->value->type);
-                    if (type_is_invalid(var->value->type))
+                    if ((err = ensure_complete_type(ira->codegen, var->value->type)))
                         return false;
 
                     if (var->value->type->id == TypeTableEntryIdMetaType)
@@ -17027,8 +17025,7 @@ static bool ir_make_type_info_defs(IrAnalyze *ira, ConstExprValue *out_val, Scop
             case TldIdContainer:
                 {
                     TypeTableEntry *type_entry = ((TldContainer *)curr_entry->value)->type_entry;
-                    ensure_complete_type(ira->codegen, type_entry);
-                    if (type_is_invalid(type_entry))
+                    if ((err = ensure_complete_type(ira->codegen, type_entry)))
                         return false;
 
                     // This is a type.
@@ -17055,11 +17052,11 @@ static bool ir_make_type_info_defs(IrAnalyze *ira, ConstExprValue *out_val, Scop
 }
 
 static ConstExprValue *ir_make_type_info_value(IrAnalyze *ira, TypeTableEntry *type_entry) {
+    Error err;
     assert(type_entry != nullptr);
     assert(!type_is_invalid(type_entry));
 
-    ensure_complete_type(ira->codegen, type_entry);
-    if (type_is_invalid(type_entry))
+    if ((err = ensure_complete_type(ira->codegen, type_entry)))
         return nullptr;
 
     const auto make_enum_field_val = [ira](ConstExprValue *enum_field_val, TypeEnumField *enum_field,
@@ -17093,8 +17090,7 @@ static ConstExprValue *ir_make_type_info_value(IrAnalyze *ira, TypeTableEntry *t
         }
 
         TypeTableEntry *type_info_pointer_type = ir_type_info_get_type(ira, "Pointer");
-        ensure_complete_type(ira->codegen, type_info_pointer_type);
-        assert(!type_is_invalid(type_info_pointer_type));
+        assertNoError(ensure_complete_type(ira->codegen, type_info_pointer_type));
 
         ConstExprValue *result = create_const_vals(1);
         result->special = ConstValSpecialStatic;
@@ -17106,8 +17102,7 @@ static ConstExprValue *ir_make_type_info_value(IrAnalyze *ira, TypeTableEntry *t
         // size: Size
         ensure_field_index(result->type, "size", 0);
         TypeTableEntry *type_info_pointer_size_type = ir_type_info_get_type(ira, "Size", type_info_pointer_type);
-        ensure_complete_type(ira->codegen, type_info_pointer_size_type);
-        assert(!type_is_invalid(type_info_pointer_size_type));
+        assertNoError(ensure_complete_type(ira->codegen, type_info_pointer_size_type));
         fields[0].special = ConstValSpecialStatic;
         fields[0].type = type_info_pointer_size_type;
         bigint_init_unsigned(&fields[0].data.x_enum_tag, size_enum_index);
@@ -18896,13 +18891,13 @@ static TypeTableEntry *ir_analyze_instruction_slice(IrAnalyze *ira, IrInstructio
 }
 
 static TypeTableEntry *ir_analyze_instruction_member_count(IrAnalyze *ira, IrInstructionMemberCount *instruction) {
+    Error err;
     IrInstruction *container = instruction->container->other;
     if (type_is_invalid(container->value.type))
         return ira->codegen->builtin_types.entry_invalid;
     TypeTableEntry *container_type = ir_resolve_type(ira, container);
 
-    ensure_complete_type(ira->codegen, container_type);
-    if (type_is_invalid(container_type))
+    if ((err = ensure_complete_type(ira->codegen, container_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     uint64_t result;
@@ -18934,13 +18929,13 @@ static TypeTableEntry *ir_analyze_instruction_member_count(IrAnalyze *ira, IrIns
 }
 
 static TypeTableEntry *ir_analyze_instruction_member_type(IrAnalyze *ira, IrInstructionMemberType *instruction) {
+    Error err;
     IrInstruction *container_type_value = instruction->container_type->other;
     TypeTableEntry *container_type = ir_resolve_type(ira, container_type_value);
     if (type_is_invalid(container_type))
         return ira->codegen->builtin_types.entry_invalid;
 
-    ensure_complete_type(ira->codegen, container_type);
-    if (type_is_invalid(container_type))
+    if ((err = ensure_complete_type(ira->codegen, container_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
 
@@ -18981,13 +18976,13 @@ static TypeTableEntry *ir_analyze_instruction_member_type(IrAnalyze *ira, IrInst
 }
 
 static TypeTableEntry *ir_analyze_instruction_member_name(IrAnalyze *ira, IrInstructionMemberName *instruction) {
+    Error err;
     IrInstruction *container_type_value = instruction->container_type->other;
     TypeTableEntry *container_type = ir_resolve_type(ira, container_type_value);
     if (type_is_invalid(container_type))
         return ira->codegen->builtin_types.entry_invalid;
 
-    ensure_complete_type(ira->codegen, container_type);
-    if (type_is_invalid(container_type))
+    if ((err = ensure_complete_type(ira->codegen, container_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     uint64_t member_index;
@@ -19068,13 +19063,13 @@ static TypeTableEntry *ir_analyze_instruction_handle(IrAnalyze *ira, IrInstructi
 }
 
 static TypeTableEntry *ir_analyze_instruction_align_of(IrAnalyze *ira, IrInstructionAlignOf *instruction) {
+    Error err;
     IrInstruction *type_value = instruction->type_value->other;
     if (type_is_invalid(type_value->value.type))
         return ira->codegen->builtin_types.entry_invalid;
     TypeTableEntry *type_entry = ir_resolve_type(ira, type_value);
 
-    type_ensure_zero_bits_known(ira->codegen, type_entry);
-    if (type_is_invalid(type_entry))
+    if ((err = type_ensure_zero_bits_known(ira->codegen, type_entry)))
         return ira->codegen->builtin_types.entry_invalid;
 
     switch (type_entry->id) {
@@ -19930,6 +19925,7 @@ static void buf_read_value_bytes(CodeGen *codegen, uint8_t *buf, ConstExprValue
 }
 
 static TypeTableEntry *ir_analyze_instruction_bit_cast(IrAnalyze *ira, IrInstructionBitCast *instruction) {
+    Error err;
     IrInstruction *dest_type_value = instruction->dest_type->other;
     TypeTableEntry *dest_type = ir_resolve_type(ira, dest_type_value);
     if (type_is_invalid(dest_type))
@@ -19940,12 +19936,10 @@ static TypeTableEntry *ir_analyze_instruction_bit_cast(IrAnalyze *ira, IrInstruc
     if (type_is_invalid(src_type))
         return ira->codegen->builtin_types.entry_invalid;
 
-    ensure_complete_type(ira->codegen, dest_type);
-    if (type_is_invalid(dest_type))
+    if ((err = ensure_complete_type(ira->codegen, dest_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
-    ensure_complete_type(ira->codegen, src_type);
-    if (type_is_invalid(src_type))
+    if ((err = ensure_complete_type(ira->codegen, src_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     if (get_codegen_ptr_type(src_type) != nullptr) {
@@ -20031,6 +20025,7 @@ static TypeTableEntry *ir_analyze_instruction_bit_cast(IrAnalyze *ira, IrInstruc
 }
 
 static TypeTableEntry *ir_analyze_instruction_int_to_ptr(IrAnalyze *ira, IrInstructionIntToPtr *instruction) {
+    Error err;
     IrInstruction *dest_type_value = instruction->dest_type->other;
     TypeTableEntry *dest_type = ir_resolve_type(ira, dest_type_value);
     if (type_is_invalid(dest_type))
@@ -20041,7 +20036,8 @@ static TypeTableEntry *ir_analyze_instruction_int_to_ptr(IrAnalyze *ira, IrInstr
         return ira->codegen->builtin_types.entry_invalid;
     }
 
-    type_ensure_zero_bits_known(ira->codegen, dest_type);
+    if ((err = type_ensure_zero_bits_known(ira->codegen, dest_type)))
+        return ira->codegen->builtin_types.entry_invalid;
     if (!type_has_bits(dest_type)) {
         ir_add_error(ira, dest_type_value,
                 buf_sprintf("type '%s' has 0 bits and cannot store information", buf_ptr(&dest_type->name)));
@@ -20174,6 +20170,7 @@ static TypeTableEntry *ir_analyze_instruction_ptr_to_int(IrAnalyze *ira, IrInstr
 }
 
 static TypeTableEntry *ir_analyze_instruction_ptr_type(IrAnalyze *ira, IrInstructionPtrType *instruction) {
+    Error err;
     TypeTableEntry *child_type = ir_resolve_type(ira, instruction->child_type->other);
     if (type_is_invalid(child_type))
         return ira->codegen->builtin_types.entry_invalid;
@@ -20191,8 +20188,7 @@ static TypeTableEntry *ir_analyze_instruction_ptr_type(IrAnalyze *ira, IrInstruc
         if (!ir_resolve_align(ira, instruction->align_value->other, &align_bytes))
             return ira->codegen->builtin_types.entry_invalid;
     } else {
-        type_ensure_zero_bits_known(ira->codegen, child_type);
-        if (type_is_invalid(child_type))
+        if ((err = type_ensure_zero_bits_known(ira->codegen, child_type)))
             return ira->codegen->builtin_types.entry_invalid;
         align_bytes = get_abi_alignment(ira->codegen, child_type);
     }
@@ -20312,22 +20308,21 @@ static TypeTableEntry *ir_analyze_instruction_arg_type(IrAnalyze *ira, IrInstruc
 }
 
 static TypeTableEntry *ir_analyze_instruction_tag_type(IrAnalyze *ira, IrInstructionTagType *instruction) {
+    Error err;
     IrInstruction *target_inst = instruction->target->other;
     TypeTableEntry *enum_type = ir_resolve_type(ira, target_inst);
     if (type_is_invalid(enum_type))
         return ira->codegen->builtin_types.entry_invalid;
 
     if (enum_type->id == TypeTableEntryIdEnum) {
-        ensure_complete_type(ira->codegen, enum_type);
-        if (type_is_invalid(enum_type))
+        if ((err = ensure_complete_type(ira->codegen, enum_type)))
             return ira->codegen->builtin_types.entry_invalid;
 
         ConstExprValue *out_val = ir_build_const_from(ira, &instruction->base);
         out_val->data.x_type = enum_type->data.enumeration.tag_int_type;
         return ira->codegen->builtin_types.entry_type;
     } else if (enum_type->id == TypeTableEntryIdUnion) {
-        ensure_complete_type(ira->codegen, enum_type);
-        if (type_is_invalid(enum_type))
+        if ((err = ensure_complete_type(ira->codegen, enum_type)))
             return ira->codegen->builtin_types.entry_invalid;
 
         AstNode *decl_node = enum_type->data.unionation.decl_node;
@@ -20830,6 +20825,7 @@ static TypeTableEntry *ir_analyze_instruction_sqrt(IrAnalyze *ira, IrInstruction
 }
 
 static TypeTableEntry *ir_analyze_instruction_enum_to_int(IrAnalyze *ira, IrInstructionEnumToInt *instruction) {
+    Error err;
     IrInstruction *target = instruction->target->other;
     if (type_is_invalid(target->value.type))
         return ira->codegen->builtin_types.entry_invalid;
@@ -20840,8 +20836,7 @@ static TypeTableEntry *ir_analyze_instruction_enum_to_int(IrAnalyze *ira, IrInst
         return ira->codegen->builtin_types.entry_invalid;
     }
 
-    type_ensure_zero_bits_known(ira->codegen, target->value.type);
-    if (type_is_invalid(target->value.type))
+    if ((err = type_ensure_zero_bits_known(ira->codegen, target->value.type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     TypeTableEntry *tag_type = target->value.type->data.enumeration.tag_int_type;
@@ -20852,6 +20847,7 @@ static TypeTableEntry *ir_analyze_instruction_enum_to_int(IrAnalyze *ira, IrInst
 }
 
 static TypeTableEntry *ir_analyze_instruction_int_to_enum(IrAnalyze *ira, IrInstructionIntToEnum *instruction) {
+    Error err;
     IrInstruction *dest_type_value = instruction->dest_type->other;
     TypeTableEntry *dest_type = ir_resolve_type(ira, dest_type_value);
     if (type_is_invalid(dest_type))
@@ -20863,8 +20859,7 @@ static TypeTableEntry *ir_analyze_instruction_int_to_enum(IrAnalyze *ira, IrInst
         return ira->codegen->builtin_types.entry_invalid;
     }
 
-    type_ensure_zero_bits_known(ira->codegen, dest_type);
-    if (type_is_invalid(dest_type))
+    if ((err = type_ensure_zero_bits_known(ira->codegen, dest_type)))
         return ira->codegen->builtin_types.entry_invalid;
 
     TypeTableEntry *tag_type = dest_type->data.enumeration.tag_int_type;
diff --git a/src/result.hpp b/src/result.hpp
new file mode 100644
index 0000000000..6c9f35c0b6
--- /dev/null
+++ b/src/result.hpp
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2018 Andrew Kelley
+ *
+ * This file is part of zig, which is MIT licensed.
+ * See http://opensource.org/licenses/MIT
+ */
+
+#ifndef ZIG_RESULT_HPP
+#define ZIG_RESULT_HPP
+
+#include "error.hpp"
+
+#include <assert.h>
+
+static inline void assertNoError(Error err) {
+    assert(err == ErrorNone);
+}
+
+template<typename T>
+struct Result {
+    T data;
+    Error err;
+
+    Result(T x) : data(x), err(ErrorNone) {}
+
+    Result(Error err) : err(err) {
+        assert(err != ErrorNone);
+    }
+
+    T unwrap() {
+        assert(err == ErrorNone);
+        return data;
+    }
+};
+
+#endif
diff --git a/src/util.hpp b/src/util.hpp
index b0402137bd..41f8feb591 100644
--- a/src/util.hpp
+++ b/src/util.hpp
@@ -21,6 +21,7 @@
 #define ATTRIBUTE_PRINTF(a, b)
 #define ATTRIBUTE_RETURNS_NOALIAS __declspec(restrict)
 #define ATTRIBUTE_NORETURN __declspec(noreturn)
+#define ATTRIBUTE_MUST_USE
 
 #else
 
@@ -28,6 +29,7 @@
 #define ATTRIBUTE_PRINTF(a, b) __attribute__((format(printf, a, b)))
 #define ATTRIBUTE_RETURNS_NOALIAS __attribute__((__malloc__))
 #define ATTRIBUTE_NORETURN __attribute__((noreturn))
+#define ATTRIBUTE_MUST_USE __attribute__((warn_unused_result))
 
 #endif
 
diff --git a/std/c/darwin.zig b/std/c/darwin.zig
index 38b10ecfb6..2e238e40eb 100644
--- a/std/c/darwin.zig
+++ b/std/c/darwin.zig
@@ -1,3 +1,5 @@
+const macho = @import("../macho.zig");
+
 extern "c" fn __error() *c_int;
 pub extern "c" fn _NSGetExecutablePath(buf: [*]u8, bufsize: *u32) c_int;
 pub extern "c" fn _dyld_get_image_header(image_index: u32) ?*mach_header;
@@ -40,6 +42,9 @@ pub extern "c" fn socket(domain: c_int, type: c_int, protocol: c_int) c_int;
 /// absolute as the header is not part of any section.
 pub extern "c" var _mh_execute_header: if (@sizeOf(usize) == 8) mach_header_64 else mach_header;
 
+pub const mach_header_64 = macho.mach_header_64;
+pub const mach_header = macho.mach_header;
+
 pub use @import("../os/darwin/errno.zig");
 
 pub const _errno = __error;
@@ -146,353 +151,6 @@ pub const Kevent = extern struct {
     udata: usize,
 };
 
-pub const mach_header = extern struct {
-    magic: u32,
-    cputype: cpu_type_t,
-    cpusubtype: cpu_subtype_t,
-    filetype: u32,
-    ncmds: u32,
-    sizeofcmds: u32,
-    flags: u32,
-};
-
-pub const mach_header_64 = extern struct {
-    magic: u32,
-    cputype: cpu_type_t,
-    cpusubtype: cpu_subtype_t,
-    filetype: u32,
-    ncmds: u32,
-    sizeofcmds: u32,
-    flags: u32,
-    reserved: u32,
-};
-
-pub const load_command = extern struct {
-    cmd: u32,
-    cmdsize: u32,
-};
-
-
-/// The symtab_command contains the offsets and sizes of the link-edit 4.3BSD
-/// "stab" style symbol table information as described in the header files
-/// <nlist.h> and <stab.h>.
-pub const symtab_command = extern struct {
-    cmd: u32, /// LC_SYMTAB
-    cmdsize: u32, /// sizeof(struct symtab_command)
-    symoff: u32, /// symbol table offset
-    nsyms: u32, /// number of symbol table entries
-    stroff: u32, /// string table offset
-    strsize: u32, /// string table size in bytes
-};
-
-/// The linkedit_data_command contains the offsets and sizes of a blob
-/// of data in the __LINKEDIT segment.  
-const linkedit_data_command = extern struct {
-    cmd: u32,/// LC_CODE_SIGNATURE, LC_SEGMENT_SPLIT_INFO, LC_FUNCTION_STARTS, LC_DATA_IN_CODE, LC_DYLIB_CODE_SIGN_DRS or LC_LINKER_OPTIMIZATION_HINT.
-    cmdsize: u32, /// sizeof(struct linkedit_data_command)
-    dataoff: u32 , /// file offset of data in __LINKEDIT segment
-    datasize: u32 , /// file size of data in __LINKEDIT segment 
-};
-
-/// The segment load command indicates that a part of this file is to be
-/// mapped into the task's address space.  The size of this segment in memory,
-/// vmsize, maybe equal to or larger than the amount to map from this file,
-/// filesize.  The file is mapped starting at fileoff to the beginning of
-/// the segment in memory, vmaddr.  The rest of the memory of the segment,
-/// if any, is allocated zero fill on demand.  The segment's maximum virtual
-/// memory protection and initial virtual memory protection are specified
-/// by the maxprot and initprot fields.  If the segment has sections then the
-/// section structures directly follow the segment command and their size is
-/// reflected in cmdsize.
-pub const segment_command = extern struct {
-    cmd: u32,/// LC_SEGMENT
-    cmdsize: u32,/// includes sizeof section structs
-    segname: [16]u8,/// segment name
-    vmaddr: u32,/// memory address of this segment
-    vmsize: u32,/// memory size of this segment
-    fileoff: u32,/// file offset of this segment
-    filesize: u32,/// amount to map from the file
-    maxprot: vm_prot_t,/// maximum VM protection
-    initprot: vm_prot_t,/// initial VM protection
-    nsects: u32,/// number of sections in segment
-    flags: u32,
-};
-
-/// The 64-bit segment load command indicates that a part of this file is to be
-/// mapped into a 64-bit task's address space.  If the 64-bit segment has
-/// sections then section_64 structures directly follow the 64-bit segment
-/// command and their size is reflected in cmdsize.
-pub const segment_command_64 = extern struct {
-    cmd: u32,               /// LC_SEGMENT_64
-    cmdsize: u32,           /// includes sizeof section_64 structs
-    segname: [16]u8,        /// segment name
-    vmaddr: u64,            /// memory address of this segment
-    vmsize: u64,            /// memory size of this segment
-    fileoff: u64,           /// file offset of this segment
-    filesize: u64,          /// amount to map from the file
-    maxprot: vm_prot_t,     /// maximum VM protection
-    initprot: vm_prot_t,    /// initial VM protection
-    nsects: u32,            /// number of sections in segment
-    flags: u32,             
-};
-
-/// A segment is made up of zero or more sections.  Non-MH_OBJECT files have
-/// all of their segments with the proper sections in each, and padded to the
-/// specified segment alignment when produced by the link editor.  The first
-/// segment of a MH_EXECUTE and MH_FVMLIB format file contains the mach_header
-/// and load commands of the object file before its first section.  The zero
-/// fill sections are always last in their segment (in all formats).  This
-/// allows the zeroed segment padding to be mapped into memory where zero fill
-/// sections might be. The gigabyte zero fill sections, those with the section
-/// type S_GB_ZEROFILL, can only be in a segment with sections of this type.
-/// These segments are then placed after all other segments.
-///
-/// The MH_OBJECT format has all of its sections in one segment for
-/// compactness.  There is no padding to a specified segment boundary and the
-/// mach_header and load commands are not part of the segment.
-///
-/// Sections with the same section name, sectname, going into the same segment,
-/// segname, are combined by the link editor.  The resulting section is aligned
-/// to the maximum alignment of the combined sections and is the new section's
-/// alignment.  The combined sections are aligned to their original alignment in
-/// the combined section.  Any padded bytes to get the specified alignment are
-/// zeroed.
-///
-/// The format of the relocation entries referenced by the reloff and nreloc
-/// fields of the section structure for mach object files is described in the
-/// header file <reloc.h>.
-pub const @"section" = extern struct {
-    sectname: [16]u8, /// name of this section
-    segname: [16]u8,  /// segment this section goes in
-    addr: u32,        /// memory address of this section
-    size: u32,        /// size in bytes of this section
-    offset: u32,      /// file offset of this section
-    @"align": u32,    /// section alignment (power of 2)
-    reloff: u32,      /// file offset of relocation entries
-    nreloc: u32,      /// number of relocation entries
-    flags: u32,       /// flags (section type and attributes
-    reserved1: u32,   /// reserved (for offset or index)
-    reserved2: u32,   /// reserved (for count or sizeof)
-};
-
-pub const section_64 = extern struct {
-    sectname: [16]u8, /// name of this section
-    segname: [16]u8,  /// segment this section goes in
-    addr: u64,        /// memory address of this section
-    size: u64,        /// size in bytes of this section
-    offset: u32,      /// file offset of this section
-    @"align": u32,    /// section alignment (power of 2)
-    reloff: u32,      /// file offset of relocation entries
-    nreloc: u32,      /// number of relocation entries
-    flags: u32,       /// flags (section type and attributes
-    reserved1: u32,   /// reserved (for offset or index)
-    reserved2: u32,   /// reserved (for count or sizeof)
-    reserved3: u32,   /// reserved
-};
-
-pub const nlist = extern struct {
-    n_strx: u32,
-    n_type: u8,
-    n_sect: u8,
-    n_desc: i16,
-    n_value: u32,
-};
-
-pub const nlist_64 = extern struct {
-    n_strx: u32,
-    n_type: u8,
-    n_sect: u8,
-    n_desc: u16,
-    n_value: u64,
-};
-
-/// After MacOS X 10.1 when a new load command is added that is required to be
-/// understood by the dynamic linker for the image to execute properly the
-/// LC_REQ_DYLD bit will be or'ed into the load command constant.  If the dynamic
-/// linker sees such a load command it it does not understand will issue a
-/// "unknown load command required for execution" error and refuse to use the
-/// image.  Other load commands without this bit that are not understood will
-/// simply be ignored.
-pub const LC_REQ_DYLD = 0x80000000;
-
-pub const LC_SEGMENT = 0x1; /// segment of this file to be mapped
-pub const LC_SYMTAB = 0x2; /// link-edit stab symbol table info
-pub const LC_SYMSEG = 0x3; /// link-edit gdb symbol table info (obsolete)
-pub const LC_THREAD = 0x4; /// thread
-pub const LC_UNIXTHREAD = 0x5; /// unix thread (includes a stack)
-pub const LC_LOADFVMLIB = 0x6; /// load a specified fixed VM shared library
-pub const LC_IDFVMLIB = 0x7; /// fixed VM shared library identification
-pub const LC_IDENT = 0x8; /// object identification info (obsolete)
-pub const LC_FVMFILE = 0x9; /// fixed VM file inclusion (internal use)
-pub const LC_PREPAGE      = 0xa; /// prepage command (internal use)
-pub const LC_DYSYMTAB = 0xb; /// dynamic link-edit symbol table info
-pub const LC_LOAD_DYLIB = 0xc; /// load a dynamically linked shared library
-pub const LC_ID_DYLIB = 0xd; /// dynamically linked shared lib ident
-pub const LC_LOAD_DYLINKER = 0xe; /// load a dynamic linker
-pub const LC_ID_DYLINKER = 0xf; /// dynamic linker identification
-pub const LC_PREBOUND_DYLIB = 0x10; /// modules prebound for a dynamically
-pub const LC_ROUTINES = 0x11; /// image routines
-pub const LC_SUB_FRAMEWORK = 0x12; /// sub framework
-pub const LC_SUB_UMBRELLA = 0x13; /// sub umbrella
-pub const LC_SUB_CLIENT = 0x14; /// sub client
-pub const LC_SUB_LIBRARY  = 0x15; /// sub library
-pub const LC_TWOLEVEL_HINTS = 0x16; /// two-level namespace lookup hints
-pub const LC_PREBIND_CKSUM  = 0x17; /// prebind checksum
-
-/// load a dynamically linked shared library that is allowed to be missing
-/// (all symbols are weak imported).
-pub const LC_LOAD_WEAK_DYLIB = (0x18 | LC_REQ_DYLD);
-
-pub const LC_SEGMENT_64 = 0x19; /// 64-bit segment of this file to be mapped
-pub const LC_ROUTINES_64 = 0x1a; /// 64-bit image routines
-pub const LC_UUID =  0x1b; /// the uuid
-pub const LC_RPATH = (0x1c | LC_REQ_DYLD); /// runpath additions
-pub const LC_CODE_SIGNATURE = 0x1d; /// local of code signature
-pub const LC_SEGMENT_SPLIT_INFO = 0x1e; /// local of info to split segments
-pub const LC_REEXPORT_DYLIB = (0x1f | LC_REQ_DYLD); /// load and re-export dylib
-pub const LC_LAZY_LOAD_DYLIB = 0x20; /// delay load of dylib until first use
-pub const LC_ENCRYPTION_INFO = 0x21; /// encrypted segment information
-pub const LC_DYLD_INFO =  0x22; /// compressed dyld information
-pub const LC_DYLD_INFO_ONLY = (0x22|LC_REQ_DYLD); /// compressed dyld information only
-pub const LC_LOAD_UPWARD_DYLIB = (0x23 | LC_REQ_DYLD); /// load upward dylib
-pub const LC_VERSION_MIN_MACOSX = 0x24; /// build for MacOSX min OS version
-pub const LC_VERSION_MIN_IPHONEOS = 0x25; /// build for iPhoneOS min OS version
-pub const LC_FUNCTION_STARTS = 0x26; /// compressed table of function start addresses
-pub const LC_DYLD_ENVIRONMENT = 0x27; /// string for dyld to treat like environment variable
-pub const LC_MAIN = (0x28|LC_REQ_DYLD); /// replacement for LC_UNIXTHREAD
-pub const LC_DATA_IN_CODE = 0x29; /// table of non-instructions in __text
-pub const LC_SOURCE_VERSION = 0x2A; /// source version used to build binary
-pub const LC_DYLIB_CODE_SIGN_DRS = 0x2B; /// Code signing DRs copied from linked dylibs
-pub const LC_ENCRYPTION_INFO_64 = 0x2C; /// 64-bit encrypted segment information
-pub const LC_LINKER_OPTION = 0x2D; /// linker options in MH_OBJECT files
-pub const LC_LINKER_OPTIMIZATION_HINT = 0x2E; /// optimization hints in MH_OBJECT files
-pub const LC_VERSION_MIN_TVOS = 0x2F; /// build for AppleTV min OS version
-pub const LC_VERSION_MIN_WATCHOS = 0x30; /// build for Watch min OS version
-pub const LC_NOTE = 0x31; /// arbitrary data included within a Mach-O file
-pub const LC_BUILD_VERSION = 0x32; /// build for platform min OS version
-
-pub const MH_MAGIC = 0xfeedface; /// the mach magic number
-pub const MH_CIGAM = 0xcefaedfe; /// NXSwapInt(MH_MAGIC)
-
-pub const MH_MAGIC_64 = 0xfeedfacf; /// the 64-bit mach magic number
-pub const MH_CIGAM_64 = 0xcffaedfe; /// NXSwapInt(MH_MAGIC_64)
-
-pub const MH_OBJECT = 0x1;  /// relocatable object file
-pub const MH_EXECUTE = 0x2;  /// demand paged executable file
-pub const MH_FVMLIB = 0x3;  /// fixed VM shared library file
-pub const MH_CORE =  0x4;  /// core file
-pub const MH_PRELOAD = 0x5;  /// preloaded executable file
-pub const MH_DYLIB = 0x6;  /// dynamically bound shared library
-pub const MH_DYLINKER = 0x7;  /// dynamic link editor
-pub const MH_BUNDLE = 0x8;  /// dynamically bound bundle file
-pub const MH_DYLIB_STUB = 0x9;  /// shared library stub for static linking only, no section contents
-pub const MH_DSYM =  0xa;  /// companion file with only debug sections
-pub const MH_KEXT_BUNDLE = 0xb;  /// x86_64 kexts
-
-// Constants for the flags field of the mach_header
-
-pub const MH_NOUNDEFS = 0x1;  /// the object file has no undefined references
-pub const MH_INCRLINK = 0x2;  /// the object file is the output of an incremental link against a base file and can't be link edited again
-pub const MH_DYLDLINK = 0x4;  /// the object file is input for the dynamic linker and can't be staticly link edited again
-pub const MH_BINDATLOAD = 0x8;  /// the object file's undefined references are bound by the dynamic linker when loaded.
-pub const MH_PREBOUND = 0x10;  /// the file has its dynamic undefined references prebound.
-pub const MH_SPLIT_SEGS = 0x20;  /// the file has its read-only and read-write segments split
-pub const MH_LAZY_INIT = 0x40;  /// the shared library init routine is to be run lazily via catching memory faults to its writeable segments (obsolete)
-pub const MH_TWOLEVEL = 0x80;  /// the image is using two-level name space bindings
-pub const MH_FORCE_FLAT = 0x100;  /// the executable is forcing all images to use flat name space bindings
-pub const MH_NOMULTIDEFS = 0x200;  /// this umbrella guarantees no multiple defintions of symbols in its sub-images so the two-level namespace hints can always be used.
-pub const MH_NOFIXPREBINDING = 0x400; /// do not have dyld notify the prebinding agent about this executable
-pub const MH_PREBINDABLE =  0x800;           /// the binary is not prebound but can have its prebinding redone. only used when MH_PREBOUND is not set.
-pub const MH_ALLMODSBOUND = 0x1000;  /// indicates that this binary binds to all two-level namespace modules of its dependent libraries. only used when MH_PREBINDABLE and MH_TWOLEVEL are both set. 
-pub const MH_SUBSECTIONS_VIA_SYMBOLS = 0x2000;/// safe to divide up the sections into sub-sections via symbols for dead code stripping
-pub const MH_CANONICAL =    0x4000;  /// the binary has been canonicalized via the unprebind operation
-pub const MH_WEAK_DEFINES = 0x8000;  /// the final linked image contains external weak symbols
-pub const MH_BINDS_TO_WEAK = 0x10000; /// the final linked image uses weak symbols
-
-pub const MH_ALLOW_STACK_EXECUTION = 0x20000;/// When this bit is set, all stacks in the task will be given stack execution privilege.  Only used in MH_EXECUTE filetypes.
-pub const MH_ROOT_SAFE = 0x40000;           /// When this bit is set, the binary declares it is safe for use in processes with uid zero
-                                         
-pub const MH_SETUID_SAFE = 0x80000;         /// When this bit is set, the binary declares it is safe for use in processes when issetugid() is true
-
-pub const MH_NO_REEXPORTED_DYLIBS = 0x100000; /// When this bit is set on a dylib, the static linker does not need to examine dependent dylibs to see if any are re-exported
-pub const MH_PIE = 0x200000;   /// When this bit is set, the OS will load the main executable at a random address.  Only used in MH_EXECUTE filetypes.
-pub const MH_DEAD_STRIPPABLE_DYLIB = 0x400000; /// Only for use on dylibs.  When linking against a dylib that has this bit set, the static linker will automatically not create a LC_LOAD_DYLIB load command to the dylib if no symbols are being referenced from the dylib.
-pub const MH_HAS_TLV_DESCRIPTORS = 0x800000; /// Contains a section of type S_THREAD_LOCAL_VARIABLES
-
-pub const MH_NO_HEAP_EXECUTION = 0x1000000; /// When this bit is set, the OS will run the main executable with a non-executable heap even on platforms (e.g. i386) that don't require it. Only used in MH_EXECUTE filetypes.
-
-pub const MH_APP_EXTENSION_SAFE = 0x02000000; /// The code was linked for use in an application extension.
-
-pub const MH_NLIST_OUTOFSYNC_WITH_DYLDINFO = 0x04000000; /// The external symbols listed in the nlist symbol table do not include all the symbols listed in the dyld info.
-
-
-/// The flags field of a section structure is separated into two parts a section
-/// type and section attributes.  The section types are mutually exclusive (it
-/// can only have one type) but the section attributes are not (it may have more
-/// than one attribute).
-/// 256 section types
-pub const SECTION_TYPE = 0x000000ff;
-pub const SECTION_ATTRIBUTES = 0xffffff00; ///  24 section attributes
-
-pub const S_REGULAR = 0x0; /// regular section
-pub const S_ZEROFILL = 0x1; /// zero fill on demand section
-pub const S_CSTRING_LITERALS = 0x2; /// section with only literal C string
-pub const S_4BYTE_LITERALS = 0x3; /// section with only 4 byte literals
-pub const S_8BYTE_LITERALS = 0x4; /// section with only 8 byte literals
-pub const S_LITERAL_POINTERS = 0x5; /// section with only pointers to
-
-
-pub const N_STAB = 0xe0; /// if any of these bits set, a symbolic debugging entry
-pub const N_PEXT = 0x10; /// private external symbol bit
-pub const N_TYPE = 0x0e; /// mask for the type bits
-pub const N_EXT = 0x01; /// external symbol bit, set for external symbols
-
-
-pub const N_GSYM = 0x20; /// global symbol: name,,NO_SECT,type,0
-pub const N_FNAME = 0x22; /// procedure name (f77 kludge): name,,NO_SECT,0,0
-pub const N_FUN = 0x24; /// procedure: name,,n_sect,linenumber,address
-pub const N_STSYM = 0x26; /// static symbol: name,,n_sect,type,address
-pub const N_LCSYM = 0x28; /// .lcomm symbol: name,,n_sect,type,address
-pub const N_BNSYM = 0x2e; /// begin nsect sym: 0,,n_sect,0,address
-pub const N_AST = 0x32; /// AST file path: name,,NO_SECT,0,0
-pub const N_OPT = 0x3c; /// emitted with gcc2_compiled and in gcc source
-pub const N_RSYM = 0x40; /// register sym: name,,NO_SECT,type,register
-pub const N_SLINE = 0x44; /// src line: 0,,n_sect,linenumber,address
-pub const N_ENSYM = 0x4e; /// end nsect sym: 0,,n_sect,0,address
-pub const N_SSYM = 0x60; /// structure elt: name,,NO_SECT,type,struct_offset
-pub const N_SO = 0x64; /// source file name: name,,n_sect,0,address
-pub const N_OSO = 0x66; /// object file name: name,,0,0,st_mtime
-pub const N_LSYM = 0x80; /// local sym: name,,NO_SECT,type,offset
-pub const N_BINCL = 0x82; /// include file beginning: name,,NO_SECT,0,sum
-pub const N_SOL = 0x84; /// #included file name: name,,n_sect,0,address
-pub const N_PARAMS =  0x86; /// compiler parameters: name,,NO_SECT,0,0
-pub const N_VERSION = 0x88; /// compiler version: name,,NO_SECT,0,0
-pub const N_OLEVEL =  0x8A; /// compiler -O level: name,,NO_SECT,0,0
-pub const N_PSYM = 0xa0; /// parameter: name,,NO_SECT,type,offset
-pub const N_EINCL = 0xa2; /// include file end: name,,NO_SECT,0,0
-pub const N_ENTRY = 0xa4; /// alternate entry: name,,n_sect,linenumber,address
-pub const N_LBRAC = 0xc0; /// left bracket: 0,,NO_SECT,nesting level,address
-pub const N_EXCL = 0xc2; /// deleted include file: name,,NO_SECT,0,sum
-pub const N_RBRAC = 0xe0; /// right bracket: 0,,NO_SECT,nesting level,address
-pub const N_BCOMM = 0xe2; /// begin common: name,,NO_SECT,0,0
-pub const N_ECOMM = 0xe4; /// end common: name,,n_sect,0,0
-pub const N_ECOML = 0xe8; /// end common (local name): 0,,n_sect,0,address
-pub const N_LENG = 0xfe; /// second stab entry with length information
-
-/// If a segment contains any sections marked with S_ATTR_DEBUG then all
-/// sections in that segment must have this attribute.  No section other than
-/// a section marked with this attribute may reference the contents of this
-/// section.  A section with this attribute may contain no symbols and must have
-/// a section type S_REGULAR.  The static linker will not copy section contents
-/// from sections with this attribute into its output file.  These sections
-/// generally contain DWARF debugging info.
-pub const S_ATTR_DEBUG = 0x02000000; /// a debug section
-
-pub const cpu_type_t = integer_t;
-pub const cpu_subtype_t = integer_t;
-pub const integer_t = c_int;
-pub const vm_prot_t = c_int;
-
 // sys/types.h on macos uses #pragma pack(4) so these checks are
 // to make sure the struct is laid out the same. These values were
 // produced from C code using the offsetof macro.
diff --git a/std/c/linux.zig b/std/c/linux.zig
index 2699e9bd09..b0dadf071d 100644
--- a/std/c/linux.zig
+++ b/std/c/linux.zig
@@ -8,3 +8,6 @@ pub const pthread_attr_t = extern struct {
     __size: [56]u8,
     __align: c_long,
 };
+
+/// See std.elf for constants for this
+pub extern fn getauxval(__type: c_ulong) c_ulong;
diff --git a/std/debug/index.zig b/std/debug/index.zig
index 2ba9a1c85f..39c41d4bc1 100644
--- a/std/debug/index.zig
+++ b/std/debug/index.zig
@@ -4,6 +4,7 @@ const mem = std.mem;
 const io = std.io;
 const os = std.os;
 const elf = std.elf;
+const macho = std.macho;
 const DW = std.dwarf;
 const ArrayList = std.ArrayList;
 const builtin = @import("builtin");
@@ -369,33 +370,7 @@ pub const OpenSelfDebugInfoError = error{
 
 pub fn openSelfDebugInfo(allocator: *mem.Allocator) !DebugInfo {
     switch (builtin.os) {
-        builtin.Os.linux => {
-            const st = try allocator.create(DebugInfo{
-                .self_exe_file = undefined,
-                .elf = undefined,
-                .debug_info = undefined,
-                .debug_abbrev = undefined,
-                .debug_str = undefined,
-                .debug_line = undefined,
-                .debug_ranges = null,
-                .abbrev_table_list = ArrayList(AbbrevTableHeader).init(allocator),
-                .compile_unit_list = ArrayList(CompileUnit).init(allocator),
-            });
-            errdefer allocator.destroy(st);
-            st.self_exe_file = try os.openSelfExe();
-            errdefer st.self_exe_file.close();
-
-            try st.elf.openFile(allocator, &st.self_exe_file);
-            errdefer st.elf.close();
-
-            st.debug_info = (try st.elf.findSection(".debug_info")) orelse return error.MissingDebugInfo;
-            st.debug_abbrev = (try st.elf.findSection(".debug_abbrev")) orelse return error.MissingDebugInfo;
-            st.debug_str = (try st.elf.findSection(".debug_str")) orelse return error.MissingDebugInfo;
-            st.debug_line = (try st.elf.findSection(".debug_line")) orelse return error.MissingDebugInfo;
-            st.debug_ranges = (try st.elf.findSection(".debug_ranges"));
-            try scanAllCompileUnits(st);
-            return st;
-        },
+        builtin.Os.linux => return openSelfDebugInfoLinux(allocator),
         builtin.Os.macosx, builtin.Os.ios => return openSelfDebugInfoMacOs(allocator),
         builtin.Os.windows => {
             // TODO: https://github.com/ziglang/zig/issues/721
@@ -405,40 +380,91 @@ pub fn openSelfDebugInfo(allocator: *mem.Allocator) !DebugInfo {
     }
 }
 
+fn openSelfDebugInfoLinux(allocator: *mem.Allocator) !DebugInfo {
+    var di = DebugInfo{
+        .self_exe_file = undefined,
+        .elf = undefined,
+        .debug_info = undefined,
+        .debug_abbrev = undefined,
+        .debug_str = undefined,
+        .debug_line = undefined,
+        .debug_ranges = null,
+        .abbrev_table_list = ArrayList(AbbrevTableHeader).init(allocator),
+        .compile_unit_list = ArrayList(CompileUnit).init(allocator),
+    };
+    di.self_exe_file = try os.openSelfExe();
+    errdefer di.self_exe_file.close();
+
+    try di.elf.openFile(allocator, &di.self_exe_file);
+    errdefer di.elf.close();
+
+    di.debug_info = (try di.elf.findSection(".debug_info")) orelse return error.MissingDebugInfo;
+    di.debug_abbrev = (try di.elf.findSection(".debug_abbrev")) orelse return error.MissingDebugInfo;
+    di.debug_str = (try di.elf.findSection(".debug_str")) orelse return error.MissingDebugInfo;
+    di.debug_line = (try di.elf.findSection(".debug_line")) orelse return error.MissingDebugInfo;
+    di.debug_ranges = (try di.elf.findSection(".debug_ranges"));
+    try scanAllCompileUnits(&di);
+    return di;
+}
+
+pub fn findElfSection(elf: *Elf, name: []const u8) ?*elf.Shdr {
+    var file_stream = io.FileInStream.init(elf.in_file);
+    const in = &file_stream.stream;
+
+    section_loop: for (elf.section_headers) |*elf_section| {
+        if (elf_section.sh_type == SHT_NULL) continue;
+
+        const name_offset = elf.string_section.offset + elf_section.name;
+        try elf.in_file.seekTo(name_offset);
+
+        for (name) |expected_c| {
+            const target_c = try in.readByte();
+            if (target_c == 0 or expected_c != target_c) continue :section_loop;
+        }
+
+        {
+            const null_byte = try in.readByte();
+            if (null_byte == 0) return elf_section;
+        }
+    }
+
+    return null;
+}
+
 fn openSelfDebugInfoMacOs(allocator: *mem.Allocator) !DebugInfo {
     const hdr = &std.c._mh_execute_header;
-    assert(hdr.magic == std.c.MH_MAGIC_64);
+    assert(hdr.magic == std.macho.MH_MAGIC_64);
 
     const hdr_base = @ptrCast([*]u8, hdr);
-    var ptr = hdr_base + @sizeOf(std.c.mach_header_64);
+    var ptr = hdr_base + @sizeOf(macho.mach_header_64);
     var ncmd: u32 = hdr.ncmds;
     const symtab = while (ncmd != 0) : (ncmd -= 1) {
-        const lc = @ptrCast(*std.c.load_command, ptr);
+        const lc = @ptrCast(*std.macho.load_command, ptr);
         switch (lc.cmd) {
-            std.c.LC_SYMTAB => break @ptrCast(*std.c.symtab_command, ptr),
+            std.macho.LC_SYMTAB => break @ptrCast(*std.macho.symtab_command, ptr),
             else => {},
         }
         ptr += lc.cmdsize; // TODO https://github.com/ziglang/zig/issues/1403
     } else {
         return error.MissingDebugInfo;
     };
-    const syms = @ptrCast([*]std.c.nlist_64, hdr_base + symtab.symoff)[0..symtab.nsyms];
+    const syms = @ptrCast([*]macho.nlist_64, hdr_base + symtab.symoff)[0..symtab.nsyms];
     const strings = @ptrCast([*]u8, hdr_base + symtab.stroff)[0..symtab.strsize];
 
     const symbols_buf = try allocator.alloc(MachoSymbol, syms.len);
 
-    var ofile: ?*std.c.nlist_64 = null;
+    var ofile: ?*macho.nlist_64 = null;
     var reloc: u64 = 0;
     var symbol_index: usize = 0;
     var last_len: u64 = 0;
     for (syms) |*sym| {
-        if (sym.n_type & std.c.N_STAB != 0) {
+        if (sym.n_type & std.macho.N_STAB != 0) {
             switch (sym.n_type) {
-                std.c.N_OSO => {
+                std.macho.N_OSO => {
                     ofile = sym;
                     reloc = 0;
                 },
-                std.c.N_FUN => {
+                std.macho.N_FUN => {
                     if (sym.n_sect == 0) {
                         last_len = sym.n_value;
                     } else {
@@ -450,7 +476,7 @@ fn openSelfDebugInfoMacOs(allocator: *mem.Allocator) !DebugInfo {
                         symbol_index += 1;
                     }
                 },
-                std.c.N_BNSYM => {
+                std.macho.N_BNSYM => {
                     if (reloc == 0) {
                         reloc = sym.n_value;
                     }
@@ -459,8 +485,8 @@ fn openSelfDebugInfoMacOs(allocator: *mem.Allocator) !DebugInfo {
             }
         }
     }
-    const sentinel = try allocator.createOne(std.c.nlist_64);
-    sentinel.* = std.c.nlist_64{
+    const sentinel = try allocator.createOne(macho.nlist_64);
+    sentinel.* = macho.nlist_64{
         .n_strx = 0,
         .n_type = 36,
         .n_sect = 0,
@@ -515,8 +541,8 @@ fn printLineFromFile(out_stream: var, line_info: *const LineInfo) !void {
 }
 
 const MachoSymbol = struct {
-    nlist: *std.c.nlist_64,
-    ofile: ?*std.c.nlist_64,
+    nlist: *macho.nlist_64,
+    ofile: ?*macho.nlist_64,
     reloc: u64,
 
     /// Returns the address from the macho file
@@ -530,9 +556,9 @@ const MachoSymbol = struct {
 };
 
 const MachOFile = struct {
-    bytes: []align(@alignOf(std.c.mach_header_64)) const u8,
-    sect_debug_info: ?*const std.c.section_64,
-    sect_debug_line: ?*const std.c.section_64,
+    bytes: []align(@alignOf(macho.mach_header_64)) const u8,
+    sect_debug_info: ?*const macho.section_64,
+    sect_debug_line: ?*const macho.section_64,
 };
 
 pub const DebugInfo = switch (builtin.os) {
@@ -542,10 +568,10 @@ pub const DebugInfo = switch (builtin.os) {
         ofiles: OFileTable,
 
         const OFileTable = std.HashMap(
-            *std.c.nlist_64,
+            *macho.nlist_64,
             MachOFile,
-            std.hash_map.getHashPtrAddrFn(*std.c.nlist_64),
-            std.hash_map.getTrivialEqlFn(*std.c.nlist_64),
+            std.hash_map.getHashPtrAddrFn(*macho.nlist_64),
+            std.hash_map.getTrivialEqlFn(*macho.nlist_64),
         );
 
         pub fn allocator(self: DebugInfo) *mem.Allocator {
@@ -563,7 +589,7 @@ pub const DebugInfo = switch (builtin.os) {
         abbrev_table_list: ArrayList(AbbrevTableHeader),
         compile_unit_list: ArrayList(CompileUnit),
 
-        pub fn allocator(self: *const DebugInfo) *mem.Allocator {
+        pub fn allocator(self: DebugInfo) *mem.Allocator {
             return self.abbrev_table_list.allocator;
         }
 
@@ -983,30 +1009,31 @@ fn getLineNumberInfoMacOs(di: *DebugInfo, symbol: MachoSymbol, target_address: u
         const ofile_path = mem.toSliceConst(u8, di.strings.ptr + ofile.n_strx);
 
         gop.kv.value = MachOFile{
-            .bytes = try std.io.readFileAllocAligned(di.ofiles.allocator, ofile_path, @alignOf(std.c.mach_header_64)),
+            .bytes = try std.io.readFileAllocAligned(di.ofiles.allocator, ofile_path, @alignOf(macho.mach_header_64)),
             .sect_debug_info = null,
             .sect_debug_line = null,
         };
-        const hdr = @ptrCast(*const std.c.mach_header_64, gop.kv.value.bytes.ptr);
-        if (hdr.magic != std.c.MH_MAGIC_64) return error.InvalidDebugInfo;
+        const hdr = @ptrCast(*const macho.mach_header_64, gop.kv.value.bytes.ptr);
+        if (hdr.magic != std.macho.MH_MAGIC_64) return error.InvalidDebugInfo;
 
         const hdr_base = @ptrCast([*]const u8, hdr);
-        var ptr = hdr_base + @sizeOf(std.c.mach_header_64);
+        var ptr = hdr_base + @sizeOf(macho.mach_header_64);
         var ncmd: u32 = hdr.ncmds;
         const segcmd = while (ncmd != 0) : (ncmd -= 1) {
-            const lc = @ptrCast(*const std.c.load_command, ptr);
+            const lc = @ptrCast(*const std.macho.load_command, ptr);
             switch (lc.cmd) {
-                std.c.LC_SEGMENT_64 => break @ptrCast(*const std.c.segment_command_64, ptr),
+                std.macho.LC_SEGMENT_64 => break @ptrCast(*const std.macho.segment_command_64, ptr),
                 else => {},
             }
             ptr += lc.cmdsize; // TODO https://github.com/ziglang/zig/issues/1403
         } else {
             return error.MissingDebugInfo;
         };
-        const sections = @alignCast(@alignOf(std.c.section_64), @ptrCast([*]const std.c.section_64, ptr + @sizeOf(std.c.segment_command_64)))[0..segcmd.nsects];
+        const sections = @alignCast(@alignOf(macho.section_64), @ptrCast([*]const macho.section_64, ptr + @sizeOf(std.macho.segment_command_64)))[0..segcmd.nsects];
         for (sections) |*sect| {
-            if (sect.flags & std.c.SECTION_TYPE == std.c.S_REGULAR and
-                (sect.flags & std.c.SECTION_ATTRIBUTES) & std.c.S_ATTR_DEBUG == std.c.S_ATTR_DEBUG) {
+            if (sect.flags & macho.SECTION_TYPE == macho.S_REGULAR and
+                (sect.flags & macho.SECTION_ATTRIBUTES) & macho.S_ATTR_DEBUG == macho.S_ATTR_DEBUG)
+            {
                 const sect_name = mem.toSliceConst(u8, &sect.sectname);
                 if (mem.eql(u8, sect_name, "__debug_line")) {
                     gop.kv.value.sect_debug_line = sect;
@@ -1052,7 +1079,7 @@ fn getLineNumberInfoMacOs(di: *DebugInfo, symbol: MachoSymbol, target_address: u
 
     const opcode_base = readByteMem(&ptr);
 
-    const standard_opcode_lengths = ptr[0..opcode_base - 1];
+    const standard_opcode_lengths = ptr[0 .. opcode_base - 1];
     ptr += opcode_base - 1;
 
     var include_directories = ArrayList([]const u8).init(di.allocator());
diff --git a/std/elf.zig b/std/elf.zig
index 8e6445c631..3d81555319 100644
--- a/std/elf.zig
+++ b/std/elf.zig
@@ -869,6 +869,11 @@ pub const Phdr = switch (@sizeOf(usize)) {
     8 => Elf64_Phdr,
     else => @compileError("expected pointer size of 32 or 64"),
 };
+pub const Shdr = switch (@sizeOf(usize)) {
+    4 => Elf32_Shdr,
+    8 => Elf64_Shdr,
+    else => @compileError("expected pointer size of 32 or 64"),
+};
 pub const Sym = switch (@sizeOf(usize)) {
     4 => Elf32_Sym,
     8 => Elf64_Sym,
diff --git a/std/macho.zig b/std/macho.zig
new file mode 100644
index 0000000000..4325810b03
--- /dev/null
+++ b/std/macho.zig
@@ -0,0 +1,348 @@
+
+pub const mach_header = extern struct {
+    magic: u32,
+    cputype: cpu_type_t,
+    cpusubtype: cpu_subtype_t,
+    filetype: u32,
+    ncmds: u32,
+    sizeofcmds: u32,
+    flags: u32,
+};
+
+pub const mach_header_64 = extern struct {
+    magic: u32,
+    cputype: cpu_type_t,
+    cpusubtype: cpu_subtype_t,
+    filetype: u32,
+    ncmds: u32,
+    sizeofcmds: u32,
+    flags: u32,
+    reserved: u32,
+};
+
+pub const load_command = extern struct {
+    cmd: u32,
+    cmdsize: u32,
+};
+
+
+/// The symtab_command contains the offsets and sizes of the link-edit 4.3BSD
+/// "stab" style symbol table information as described in the header files
+/// <nlist.h> and <stab.h>.
+pub const symtab_command = extern struct {
+    cmd: u32, /// LC_SYMTAB
+    cmdsize: u32, /// sizeof(struct symtab_command)
+    symoff: u32, /// symbol table offset
+    nsyms: u32, /// number of symbol table entries
+    stroff: u32, /// string table offset
+    strsize: u32, /// string table size in bytes
+};
+
+/// The linkedit_data_command contains the offsets and sizes of a blob
+/// of data in the __LINKEDIT segment.  
+const linkedit_data_command = extern struct {
+    cmd: u32,/// LC_CODE_SIGNATURE, LC_SEGMENT_SPLIT_INFO, LC_FUNCTION_STARTS, LC_DATA_IN_CODE, LC_DYLIB_CODE_SIGN_DRS or LC_LINKER_OPTIMIZATION_HINT.
+    cmdsize: u32, /// sizeof(struct linkedit_data_command)
+    dataoff: u32 , /// file offset of data in __LINKEDIT segment
+    datasize: u32 , /// file size of data in __LINKEDIT segment 
+};
+
+/// The segment load command indicates that a part of this file is to be
+/// mapped into the task's address space.  The size of this segment in memory,
+/// vmsize, maybe equal to or larger than the amount to map from this file,
+/// filesize.  The file is mapped starting at fileoff to the beginning of
+/// the segment in memory, vmaddr.  The rest of the memory of the segment,
+/// if any, is allocated zero fill on demand.  The segment's maximum virtual
+/// memory protection and initial virtual memory protection are specified
+/// by the maxprot and initprot fields.  If the segment has sections then the
+/// section structures directly follow the segment command and their size is
+/// reflected in cmdsize.
+pub const segment_command = extern struct {
+    cmd: u32,/// LC_SEGMENT
+    cmdsize: u32,/// includes sizeof section structs
+    segname: [16]u8,/// segment name
+    vmaddr: u32,/// memory address of this segment
+    vmsize: u32,/// memory size of this segment
+    fileoff: u32,/// file offset of this segment
+    filesize: u32,/// amount to map from the file
+    maxprot: vm_prot_t,/// maximum VM protection
+    initprot: vm_prot_t,/// initial VM protection
+    nsects: u32,/// number of sections in segment
+    flags: u32,
+};
+
+/// The 64-bit segment load command indicates that a part of this file is to be
+/// mapped into a 64-bit task's address space.  If the 64-bit segment has
+/// sections then section_64 structures directly follow the 64-bit segment
+/// command and their size is reflected in cmdsize.
+pub const segment_command_64 = extern struct {
+    cmd: u32,               /// LC_SEGMENT_64
+    cmdsize: u32,           /// includes sizeof section_64 structs
+    segname: [16]u8,        /// segment name
+    vmaddr: u64,            /// memory address of this segment
+    vmsize: u64,            /// memory size of this segment
+    fileoff: u64,           /// file offset of this segment
+    filesize: u64,          /// amount to map from the file
+    maxprot: vm_prot_t,     /// maximum VM protection
+    initprot: vm_prot_t,    /// initial VM protection
+    nsects: u32,            /// number of sections in segment
+    flags: u32,             
+};
+
+/// A segment is made up of zero or more sections.  Non-MH_OBJECT files have
+/// all of their segments with the proper sections in each, and padded to the
+/// specified segment alignment when produced by the link editor.  The first
+/// segment of a MH_EXECUTE and MH_FVMLIB format file contains the mach_header
+/// and load commands of the object file before its first section.  The zero
+/// fill sections are always last in their segment (in all formats).  This
+/// allows the zeroed segment padding to be mapped into memory where zero fill
+/// sections might be. The gigabyte zero fill sections, those with the section
+/// type S_GB_ZEROFILL, can only be in a segment with sections of this type.
+/// These segments are then placed after all other segments.
+///
+/// The MH_OBJECT format has all of its sections in one segment for
+/// compactness.  There is no padding to a specified segment boundary and the
+/// mach_header and load commands are not part of the segment.
+///
+/// Sections with the same section name, sectname, going into the same segment,
+/// segname, are combined by the link editor.  The resulting section is aligned
+/// to the maximum alignment of the combined sections and is the new section's
+/// alignment.  The combined sections are aligned to their original alignment in
+/// the combined section.  Any padded bytes to get the specified alignment are
+/// zeroed.
+///
+/// The format of the relocation entries referenced by the reloff and nreloc
+/// fields of the section structure for mach object files is described in the
+/// header file <reloc.h>.
+pub const @"section" = extern struct {
+    sectname: [16]u8, /// name of this section
+    segname: [16]u8,  /// segment this section goes in
+    addr: u32,        /// memory address of this section
+    size: u32,        /// size in bytes of this section
+    offset: u32,      /// file offset of this section
+    @"align": u32,    /// section alignment (power of 2)
+    reloff: u32,      /// file offset of relocation entries
+    nreloc: u32,      /// number of relocation entries
+    flags: u32,       /// flags (section type and attributes
+    reserved1: u32,   /// reserved (for offset or index)
+    reserved2: u32,   /// reserved (for count or sizeof)
+};
+
+pub const section_64 = extern struct {
+    sectname: [16]u8, /// name of this section
+    segname: [16]u8,  /// segment this section goes in
+    addr: u64,        /// memory address of this section
+    size: u64,        /// size in bytes of this section
+    offset: u32,      /// file offset of this section
+    @"align": u32,    /// section alignment (power of 2)
+    reloff: u32,      /// file offset of relocation entries
+    nreloc: u32,      /// number of relocation entries
+    flags: u32,       /// flags (section type and attributes
+    reserved1: u32,   /// reserved (for offset or index)
+    reserved2: u32,   /// reserved (for count or sizeof)
+    reserved3: u32,   /// reserved
+};
+
+pub const nlist = extern struct {
+    n_strx: u32,
+    n_type: u8,
+    n_sect: u8,
+    n_desc: i16,
+    n_value: u32,
+};
+
+pub const nlist_64 = extern struct {
+    n_strx: u32,
+    n_type: u8,
+    n_sect: u8,
+    n_desc: u16,
+    n_value: u64,
+};
+
+/// After MacOS X 10.1 when a new load command is added that is required to be
+/// understood by the dynamic linker for the image to execute properly the
+/// LC_REQ_DYLD bit will be or'ed into the load command constant.  If the dynamic
+/// linker sees such a load command it it does not understand will issue a
+/// "unknown load command required for execution" error and refuse to use the
+/// image.  Other load commands without this bit that are not understood will
+/// simply be ignored.
+pub const LC_REQ_DYLD = 0x80000000;
+
+pub const LC_SEGMENT = 0x1; /// segment of this file to be mapped
+pub const LC_SYMTAB = 0x2; /// link-edit stab symbol table info
+pub const LC_SYMSEG = 0x3; /// link-edit gdb symbol table info (obsolete)
+pub const LC_THREAD = 0x4; /// thread
+pub const LC_UNIXTHREAD = 0x5; /// unix thread (includes a stack)
+pub const LC_LOADFVMLIB = 0x6; /// load a specified fixed VM shared library
+pub const LC_IDFVMLIB = 0x7; /// fixed VM shared library identification
+pub const LC_IDENT = 0x8; /// object identification info (obsolete)
+pub const LC_FVMFILE = 0x9; /// fixed VM file inclusion (internal use)
+pub const LC_PREPAGE      = 0xa; /// prepage command (internal use)
+pub const LC_DYSYMTAB = 0xb; /// dynamic link-edit symbol table info
+pub const LC_LOAD_DYLIB = 0xc; /// load a dynamically linked shared library
+pub const LC_ID_DYLIB = 0xd; /// dynamically linked shared lib ident
+pub const LC_LOAD_DYLINKER = 0xe; /// load a dynamic linker
+pub const LC_ID_DYLINKER = 0xf; /// dynamic linker identification
+pub const LC_PREBOUND_DYLIB = 0x10; /// modules prebound for a dynamically
+pub const LC_ROUTINES = 0x11; /// image routines
+pub const LC_SUB_FRAMEWORK = 0x12; /// sub framework
+pub const LC_SUB_UMBRELLA = 0x13; /// sub umbrella
+pub const LC_SUB_CLIENT = 0x14; /// sub client
+pub const LC_SUB_LIBRARY  = 0x15; /// sub library
+pub const LC_TWOLEVEL_HINTS = 0x16; /// two-level namespace lookup hints
+pub const LC_PREBIND_CKSUM  = 0x17; /// prebind checksum
+
+/// load a dynamically linked shared library that is allowed to be missing
+/// (all symbols are weak imported).
+pub const LC_LOAD_WEAK_DYLIB = (0x18 | LC_REQ_DYLD);
+
+pub const LC_SEGMENT_64 = 0x19; /// 64-bit segment of this file to be mapped
+pub const LC_ROUTINES_64 = 0x1a; /// 64-bit image routines
+pub const LC_UUID =  0x1b; /// the uuid
+pub const LC_RPATH = (0x1c | LC_REQ_DYLD); /// runpath additions
+pub const LC_CODE_SIGNATURE = 0x1d; /// local of code signature
+pub const LC_SEGMENT_SPLIT_INFO = 0x1e; /// local of info to split segments
+pub const LC_REEXPORT_DYLIB = (0x1f | LC_REQ_DYLD); /// load and re-export dylib
+pub const LC_LAZY_LOAD_DYLIB = 0x20; /// delay load of dylib until first use
+pub const LC_ENCRYPTION_INFO = 0x21; /// encrypted segment information
+pub const LC_DYLD_INFO =  0x22; /// compressed dyld information
+pub const LC_DYLD_INFO_ONLY = (0x22|LC_REQ_DYLD); /// compressed dyld information only
+pub const LC_LOAD_UPWARD_DYLIB = (0x23 | LC_REQ_DYLD); /// load upward dylib
+pub const LC_VERSION_MIN_MACOSX = 0x24; /// build for MacOSX min OS version
+pub const LC_VERSION_MIN_IPHONEOS = 0x25; /// build for iPhoneOS min OS version
+pub const LC_FUNCTION_STARTS = 0x26; /// compressed table of function start addresses
+pub const LC_DYLD_ENVIRONMENT = 0x27; /// string for dyld to treat like environment variable
+pub const LC_MAIN = (0x28|LC_REQ_DYLD); /// replacement for LC_UNIXTHREAD
+pub const LC_DATA_IN_CODE = 0x29; /// table of non-instructions in __text
+pub const LC_SOURCE_VERSION = 0x2A; /// source version used to build binary
+pub const LC_DYLIB_CODE_SIGN_DRS = 0x2B; /// Code signing DRs copied from linked dylibs
+pub const LC_ENCRYPTION_INFO_64 = 0x2C; /// 64-bit encrypted segment information
+pub const LC_LINKER_OPTION = 0x2D; /// linker options in MH_OBJECT files
+pub const LC_LINKER_OPTIMIZATION_HINT = 0x2E; /// optimization hints in MH_OBJECT files
+pub const LC_VERSION_MIN_TVOS = 0x2F; /// build for AppleTV min OS version
+pub const LC_VERSION_MIN_WATCHOS = 0x30; /// build for Watch min OS version
+pub const LC_NOTE = 0x31; /// arbitrary data included within a Mach-O file
+pub const LC_BUILD_VERSION = 0x32; /// build for platform min OS version
+
+pub const MH_MAGIC = 0xfeedface; /// the mach magic number
+pub const MH_CIGAM = 0xcefaedfe; /// NXSwapInt(MH_MAGIC)
+
+pub const MH_MAGIC_64 = 0xfeedfacf; /// the 64-bit mach magic number
+pub const MH_CIGAM_64 = 0xcffaedfe; /// NXSwapInt(MH_MAGIC_64)
+
+pub const MH_OBJECT = 0x1;  /// relocatable object file
+pub const MH_EXECUTE = 0x2;  /// demand paged executable file
+pub const MH_FVMLIB = 0x3;  /// fixed VM shared library file
+pub const MH_CORE =  0x4;  /// core file
+pub const MH_PRELOAD = 0x5;  /// preloaded executable file
+pub const MH_DYLIB = 0x6;  /// dynamically bound shared library
+pub const MH_DYLINKER = 0x7;  /// dynamic link editor
+pub const MH_BUNDLE = 0x8;  /// dynamically bound bundle file
+pub const MH_DYLIB_STUB = 0x9;  /// shared library stub for static linking only, no section contents
+pub const MH_DSYM =  0xa;  /// companion file with only debug sections
+pub const MH_KEXT_BUNDLE = 0xb;  /// x86_64 kexts
+
+// Constants for the flags field of the mach_header
+
+pub const MH_NOUNDEFS = 0x1;  /// the object file has no undefined references
+pub const MH_INCRLINK = 0x2;  /// the object file is the output of an incremental link against a base file and can't be link edited again
+pub const MH_DYLDLINK = 0x4;  /// the object file is input for the dynamic linker and can't be staticly link edited again
+pub const MH_BINDATLOAD = 0x8;  /// the object file's undefined references are bound by the dynamic linker when loaded.
+pub const MH_PREBOUND = 0x10;  /// the file has its dynamic undefined references prebound.
+pub const MH_SPLIT_SEGS = 0x20;  /// the file has its read-only and read-write segments split
+pub const MH_LAZY_INIT = 0x40;  /// the shared library init routine is to be run lazily via catching memory faults to its writeable segments (obsolete)
+pub const MH_TWOLEVEL = 0x80;  /// the image is using two-level name space bindings
+pub const MH_FORCE_FLAT = 0x100;  /// the executable is forcing all images to use flat name space bindings
+pub const MH_NOMULTIDEFS = 0x200;  /// this umbrella guarantees no multiple defintions of symbols in its sub-images so the two-level namespace hints can always be used.
+pub const MH_NOFIXPREBINDING = 0x400; /// do not have dyld notify the prebinding agent about this executable
+pub const MH_PREBINDABLE =  0x800;           /// the binary is not prebound but can have its prebinding redone. only used when MH_PREBOUND is not set.
+pub const MH_ALLMODSBOUND = 0x1000;  /// indicates that this binary binds to all two-level namespace modules of its dependent libraries. only used when MH_PREBINDABLE and MH_TWOLEVEL are both set. 
+pub const MH_SUBSECTIONS_VIA_SYMBOLS = 0x2000;/// safe to divide up the sections into sub-sections via symbols for dead code stripping
+pub const MH_CANONICAL =    0x4000;  /// the binary has been canonicalized via the unprebind operation
+pub const MH_WEAK_DEFINES = 0x8000;  /// the final linked image contains external weak symbols
+pub const MH_BINDS_TO_WEAK = 0x10000; /// the final linked image uses weak symbols
+
+pub const MH_ALLOW_STACK_EXECUTION = 0x20000;/// When this bit is set, all stacks in the task will be given stack execution privilege.  Only used in MH_EXECUTE filetypes.
+pub const MH_ROOT_SAFE = 0x40000;           /// When this bit is set, the binary declares it is safe for use in processes with uid zero
+                                         
+pub const MH_SETUID_SAFE = 0x80000;         /// When this bit is set, the binary declares it is safe for use in processes when issetugid() is true
+
+pub const MH_NO_REEXPORTED_DYLIBS = 0x100000; /// When this bit is set on a dylib, the static linker does not need to examine dependent dylibs to see if any are re-exported
+pub const MH_PIE = 0x200000;   /// When this bit is set, the OS will load the main executable at a random address.  Only used in MH_EXECUTE filetypes.
+pub const MH_DEAD_STRIPPABLE_DYLIB = 0x400000; /// Only for use on dylibs.  When linking against a dylib that has this bit set, the static linker will automatically not create a LC_LOAD_DYLIB load command to the dylib if no symbols are being referenced from the dylib.
+pub const MH_HAS_TLV_DESCRIPTORS = 0x800000; /// Contains a section of type S_THREAD_LOCAL_VARIABLES
+
+pub const MH_NO_HEAP_EXECUTION = 0x1000000; /// When this bit is set, the OS will run the main executable with a non-executable heap even on platforms (e.g. i386) that don't require it. Only used in MH_EXECUTE filetypes.
+
+pub const MH_APP_EXTENSION_SAFE = 0x02000000; /// The code was linked for use in an application extension.
+
+pub const MH_NLIST_OUTOFSYNC_WITH_DYLDINFO = 0x04000000; /// The external symbols listed in the nlist symbol table do not include all the symbols listed in the dyld info.
+
+
+/// The flags field of a section structure is separated into two parts a section
+/// type and section attributes.  The section types are mutually exclusive (it
+/// can only have one type) but the section attributes are not (it may have more
+/// than one attribute).
+/// 256 section types
+pub const SECTION_TYPE = 0x000000ff;
+pub const SECTION_ATTRIBUTES = 0xffffff00; ///  24 section attributes
+
+pub const S_REGULAR = 0x0; /// regular section
+pub const S_ZEROFILL = 0x1; /// zero fill on demand section
+pub const S_CSTRING_LITERALS = 0x2; /// section with only literal C string
+pub const S_4BYTE_LITERALS = 0x3; /// section with only 4 byte literals
+pub const S_8BYTE_LITERALS = 0x4; /// section with only 8 byte literals
+pub const S_LITERAL_POINTERS = 0x5; /// section with only pointers to
+
+
+pub const N_STAB = 0xe0; /// if any of these bits set, a symbolic debugging entry
+pub const N_PEXT = 0x10; /// private external symbol bit
+pub const N_TYPE = 0x0e; /// mask for the type bits
+pub const N_EXT = 0x01; /// external symbol bit, set for external symbols
+
+
+pub const N_GSYM = 0x20; /// global symbol: name,,NO_SECT,type,0
+pub const N_FNAME = 0x22; /// procedure name (f77 kludge): name,,NO_SECT,0,0
+pub const N_FUN = 0x24; /// procedure: name,,n_sect,linenumber,address
+pub const N_STSYM = 0x26; /// static symbol: name,,n_sect,type,address
+pub const N_LCSYM = 0x28; /// .lcomm symbol: name,,n_sect,type,address
+pub const N_BNSYM = 0x2e; /// begin nsect sym: 0,,n_sect,0,address
+pub const N_AST = 0x32; /// AST file path: name,,NO_SECT,0,0
+pub const N_OPT = 0x3c; /// emitted with gcc2_compiled and in gcc source
+pub const N_RSYM = 0x40; /// register sym: name,,NO_SECT,type,register
+pub const N_SLINE = 0x44; /// src line: 0,,n_sect,linenumber,address
+pub const N_ENSYM = 0x4e; /// end nsect sym: 0,,n_sect,0,address
+pub const N_SSYM = 0x60; /// structure elt: name,,NO_SECT,type,struct_offset
+pub const N_SO = 0x64; /// source file name: name,,n_sect,0,address
+pub const N_OSO = 0x66; /// object file name: name,,0,0,st_mtime
+pub const N_LSYM = 0x80; /// local sym: name,,NO_SECT,type,offset
+pub const N_BINCL = 0x82; /// include file beginning: name,,NO_SECT,0,sum
+pub const N_SOL = 0x84; /// #included file name: name,,n_sect,0,address
+pub const N_PARAMS =  0x86; /// compiler parameters: name,,NO_SECT,0,0
+pub const N_VERSION = 0x88; /// compiler version: name,,NO_SECT,0,0
+pub const N_OLEVEL =  0x8A; /// compiler -O level: name,,NO_SECT,0,0
+pub const N_PSYM = 0xa0; /// parameter: name,,NO_SECT,type,offset
+pub const N_EINCL = 0xa2; /// include file end: name,,NO_SECT,0,0
+pub const N_ENTRY = 0xa4; /// alternate entry: name,,n_sect,linenumber,address
+pub const N_LBRAC = 0xc0; /// left bracket: 0,,NO_SECT,nesting level,address
+pub const N_EXCL = 0xc2; /// deleted include file: name,,NO_SECT,0,sum
+pub const N_RBRAC = 0xe0; /// right bracket: 0,,NO_SECT,nesting level,address
+pub const N_BCOMM = 0xe2; /// begin common: name,,NO_SECT,0,0
+pub const N_ECOMM = 0xe4; /// end common: name,,n_sect,0,0
+pub const N_ECOML = 0xe8; /// end common (local name): 0,,n_sect,0,address
+pub const N_LENG = 0xfe; /// second stab entry with length information
+
+/// If a segment contains any sections marked with S_ATTR_DEBUG then all
+/// sections in that segment must have this attribute.  No section other than
+/// a section marked with this attribute may reference the contents of this
+/// section.  A section with this attribute may contain no symbols and must have
+/// a section type S_REGULAR.  The static linker will not copy section contents
+/// from sections with this attribute into its output file.  These sections
+/// generally contain DWARF debugging info.
+pub const S_ATTR_DEBUG = 0x02000000; /// a debug section
+
+pub const cpu_type_t = integer_t;
+pub const cpu_subtype_t = integer_t;
+pub const integer_t = c_int;
+pub const vm_prot_t = c_int;
+
diff --git a/std/os/index.zig b/std/os/index.zig
index a0b6e6bf45..29d887e214 100644
--- a/std/os/index.zig
+++ b/std/os/index.zig
@@ -635,6 +635,35 @@ fn posixExecveErrnoToErr(err: usize) PosixExecveError {
 pub var linux_aux_raw = []usize{0} ** 38;
 pub var posix_environ_raw: [][*]u8 = undefined;
 
+/// See std.elf for the constants.
+pub fn linuxGetAuxVal(index: usize) usize {
+    if (builtin.link_libc) {
+        return usize(std.c.getauxval(index));
+    } else {
+        return linux_aux_raw[index];
+    }
+}
+
+pub fn getBaseAddress() usize {
+    switch (builtin.os) {
+        builtin.Os.linux => {
+            const base = linuxGetAuxVal(std.elf.AT_BASE);
+            if (base != 0) {
+                return base;
+            }
+            const phdr = linuxGetAuxVal(std.elf.AT_PHDR);
+            const ElfHeader = switch (@sizeOf(usize)) {
+                4 => std.elf.Elf32_Ehdr,
+                8 => std.elf.Elf64_Ehdr,
+                else => @compileError("Unsupported architecture"),
+            };
+            return phdr - @sizeOf(ElfHeader);
+        },
+        builtin.Os.macosx => return @ptrToInt(&std.c._mh_execute_header),
+        else => @compileError("Unsupported OS"),
+    }
+}
+
 /// Caller must free result when done.
 /// TODO make this go through libc when we have it
 pub fn getEnvMap(allocator: *Allocator) !BufMap {