Merge pull request #22239 from mlugg/runtime-store-comptime-only

Sema: disallow runtime stores to pointers with comptime-only element types

Resolves: #22175

src/Sema.zig

@@ -3628,6 +3628,10 @@ fn zirAllocExtended(
         }
     }
 
+    if (small.has_type and try var_ty.comptimeOnlySema(pt)) {
+        return sema.analyzeComptimeAlloc(block, var_ty, alignment);
+    }
+
     if (small.has_type) {
         if (!small.is_const) {
             try sema.validateVarType(block, ty_src, var_ty, false);
@@ -4075,7 +4079,7 @@ fn zirAlloc(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.I
     const ty_src = block.src(.{ .node_offset_var_decl_ty = inst_data.src_node });
 
     const var_ty = try sema.resolveType(block, ty_src, inst_data.operand);
-    if (block.is_comptime) {
+    if (block.is_comptime or try var_ty.comptimeOnlySema(pt)) {
         return sema.analyzeComptimeAlloc(block, var_ty, .none);
     }
     if (sema.func_is_naked and try var_ty.hasRuntimeBitsSema(pt)) {
@@ -30675,6 +30679,18 @@ fn coerceExtra(
         else => {},
     }
 
+    const can_coerce_to = switch (dest_ty.zigTypeTag(zcu)) {
+        .noreturn, .@"opaque" => false,
+        else => true,
+    };
+
+    if (can_coerce_to) {
+        // undefined to anything. We do this after the big switch above so that
+        // special logic has a chance to run first, such as `*[N]T` to `[]T` which
+        // should initialize the length field of the slice.
+        if (maybe_inst_val) |val| if (val.toIntern() == .undef) return pt.undefRef(dest_ty);
+    }
+
     if (!opts.report_err) return error.NotCoercible;
 
     if (opts.is_ret and dest_ty.zigTypeTag(zcu) == .noreturn) {
@@ -30692,15 +30708,14 @@ fn coerceExtra(
         return sema.failWithOwnedErrorMsg(block, msg);
     }
 
-    // undefined to anything. We do this after the big switch above so that
-    // special logic has a chance to run first, such as `*[N]T` to `[]T` which
-    // should initialize the length field of the slice.
-    if (maybe_inst_val) |val| if (val.toIntern() == .undef) return pt.undefRef(dest_ty);
-
     const msg = msg: {
         const msg = try sema.errMsg(inst_src, "expected type '{}', found '{}'", .{ dest_ty.fmt(pt), inst_ty.fmt(pt) });
         errdefer msg.destroy(sema.gpa);
 
+        if (!can_coerce_to) {
+            try sema.errNote(inst_src, msg, "cannot coerce to '{}'", .{dest_ty.fmt(pt)});
+        }
+
         // E!T to T
         if (inst_ty.zigTypeTag(zcu) == .error_union and
             (try sema.coerceInMemoryAllowed(block, inst_ty.errorUnionPayload(zcu), dest_ty, false, target, dest_ty_src, inst_src, maybe_inst_val)) == .ok)
@@ -31927,6 +31942,17 @@ fn storePtr2(
         } else break :rs ptr_src;
     } else ptr_src;
 
+    // We're performing the store at runtime; as such, we need to make sure the pointee type
+    // is not comptime-only. We can hit this case with a `@ptrFromInt` pointer.
+    if (try elem_ty.comptimeOnlySema(pt)) {
+        return sema.failWithOwnedErrorMsg(block, msg: {
+            const msg = try sema.errMsg(src, "cannot store comptime-only type '{}' at runtime", .{elem_ty.fmt(pt)});
+            errdefer msg.destroy(sema.gpa);
+            try sema.errNote(ptr_src, msg, "operation is runtime due to this pointer", .{});
+            break :msg msg;
+        });
+    }
+
     // We do this after the possible comptime store above, for the case of field_ptr stores
     // to unions because we want the comptime tag to be set, even if the field type is void.
     if ((try sema.typeHasOnePossibleValue(elem_ty)) != null) {

test/cases/compile_errors/store_comptime_only_type_to_runtime_pointer.zig

@@ -0,0 +1,42 @@
+export fn a() void {
+    const p: *fn () void = @ptrFromInt(4);
+    p.* = undefined;
+}
+
+export fn b(p: *anyopaque) void {
+    p.* = undefined;
+}
+
+export fn c(p: *anyopaque, q: *anyopaque) void {
+    p.* = q.*;
+}
+
+const Opaque = opaque {};
+export fn d(p: *Opaque) void {
+    p.* = undefined;
+}
+
+export fn e() void {
+    const p: *comptime_int = @ptrFromInt(16);
+    p.* = undefined;
+}
+
+export fn f() void {
+    const p: **comptime_int = @ptrFromInt(16); // double pointer ('*comptime_int' is comptime-only)
+    p.* = undefined;
+}
+
+// error
+//
+// :3:9: error: cannot store comptime-only type 'fn () void' at runtime
+// :3:6: note: operation is runtime due to this pointer
+// :7:11: error: expected type 'anyopaque', found '@TypeOf(undefined)'
+// :7:11: note: cannot coerce to 'anyopaque'
+// :11:12: error: cannot load opaque type 'anyopaque'
+// :16:11: error: expected type 'tmp.Opaque', found '@TypeOf(undefined)'
+// :16:11: note: cannot coerce to 'tmp.Opaque'
+// :14:16: note: opaque declared here
+// :21:9: error: cannot store comptime-only type 'comptime_int' at runtime
+// :21:6: note: operation is runtime due to this pointer
+// :26:9: error: cannot store comptime-only type '*comptime_int' at runtime
+// :26:6: note: operation is runtime due to this pointer