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Sema: copy pointer alignment to union field pointers

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This implements the semantics as discussed in today's compiler meeting,
where the alignment of pointers to fields of default-layout unions
cannot exceed the field's alignment.

Resolves: #15878
This commit is contained in:
mlugg 2023-06-10 01:23:17 +01:00
parent 3f04231600
commit 2611d97fb0
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GPG Key ID: 58978E823BDE3EF9
2 changed files with 119 additions and 3 deletions
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13
src/Sema.zig
View File

@ -26060,6 +26060,7 @@ fn unionFieldPtr(
assert(unresolved_union_ty.zigTypeTag(mod) == .Union);
const union_ptr_ty = sema.typeOf(union_ptr);
const union_ptr_info = union_ptr_ty.ptrInfo(mod);
const union_ty = try sema.resolveTypeFields(unresolved_union_ty);
const union_obj = mod.typeToUnion(union_ty).?;
const field_index = try sema.unionFieldIndex(block, union_ty, field_name, field_name_src);
@ -26067,10 +26068,16 @@ fn unionFieldPtr(
const ptr_field_ty = try mod.ptrType(.{
.child = field.ty.toIntern(),
.flags = .{
.is_const = !union_ptr_ty.ptrIsMutable(mod),
.is_volatile = union_ptr_ty.isVolatilePtr(mod),
.address_space = union_ptr_ty.ptrAddressSpace(mod),
.is_const = union_ptr_info.flags.is_const,
.is_volatile = union_ptr_info.flags.is_volatile,
.address_space = union_ptr_info.flags.address_space,
.alignment = if (union_obj.layout == .Auto) blk: {
const union_align = union_ptr_info.flags.alignment.toByteUnitsOptional() orelse try sema.typeAbiAlignment(union_ty);
const field_align = try sema.unionFieldAlignment(field);
break :blk InternPool.Alignment.fromByteUnits(@min(union_align, field_align));
} else union_ptr_info.flags.alignment,
},
.packed_offset = union_ptr_info.packed_offset,
});
const enum_field_index = @as(u32, @intCast(union_obj.tag_ty.enumFieldIndex(field_name, mod).?));

109
test/behavior/union.zig
View File

@ -1583,3 +1583,112 @@ test "coerce enum literal to union in result loc" {
try U.doTest(true);
try comptime U.doTest(true);
}
test "defined-layout union field pointer has correct alignment" {
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest; // TODO
const S = struct {
fn doTheTest(comptime U: type) !void {
var a: U = .{ .x = 123 };
var b: U align(1) = .{ .x = 456 };
var c: U align(64) = .{ .x = 789 };
const ap = &a.x;
const bp = &b.x;
const cp = &c.x;
comptime assert(@TypeOf(ap) == *u32);
comptime assert(@TypeOf(bp) == *align(1) u32);
comptime assert(@TypeOf(cp) == *align(64) u32);
try expectEqual(@as(u32, 123), ap.*);
try expectEqual(@as(u32, 456), bp.*);
try expectEqual(@as(u32, 789), cp.*);
}
};
const U1 = extern union { x: u32 };
const U2 = packed union { x: u32 };
try S.doTheTest(U1);
try S.doTheTest(U2);
try comptime S.doTheTest(U1);
try comptime S.doTheTest(U2);
}
test "undefined-layout union field pointer has correct alignment" {
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest; // TODO
const S = struct {
fn doTheTest(comptime U: type) !void {
var a: U = .{ .x = 123 };
var b: U align(1) = .{ .x = 456 };
var c: U align(64) = .{ .x = 789 };
const ap = &a.x;
const bp = &b.x;
const cp = &c.x;
comptime assert(@TypeOf(ap) == *u32);
comptime assert(@TypeOf(bp) == *align(1) u32);
comptime assert(@TypeOf(cp) == *u32); // undefined layout so does not inherit larger aligns
try expectEqual(@as(u32, 123), ap.*);
try expectEqual(@as(u32, 456), bp.*);
try expectEqual(@as(u32, 789), cp.*);
}
};
const U1 = union { x: u32 };
const U2 = union(enum) { x: u32 };
try S.doTheTest(U1);
try S.doTheTest(U2);
try comptime S.doTheTest(U1);
try comptime S.doTheTest(U2);
}
test "packed union field pointer has correct alignment" {
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest; // TODO
const U = packed union { x: u20 };
const S = packed struct(u24) { a: u2, u: U, b: u2 };
var a: S = undefined;
var b: S align(1) = undefined;
var c: S align(64) = undefined;
const ap = &a.u.x;
const bp = &b.u.x;
const cp = &c.u.x;
comptime assert(@TypeOf(ap) == *align(4:2:3) u20);
comptime assert(@TypeOf(bp) == *align(1:2:3) u20);
comptime assert(@TypeOf(cp) == *align(64:2:3) u20);
a.u = .{ .x = 123 };
b.u = .{ .x = 456 };
c.u = .{ .x = 789 };
try expectEqual(@as(u20, 123), ap.*);
try expectEqual(@as(u20, 456), bp.*);
try expectEqual(@as(u20, 789), cp.*);
}