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codegen: fix taking the address of a zero-bit field in a zero-bit struct

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Normally when we want a pointer to the end of a struct we just add 1 to
the struct pointer.  However, when it is a zero-bit struct, the pointer
type being used during lowering is often a dummy pointer type that
actually points to a non-zero-bit type, so we actually want to add 0
instead, since a zero-bit struct begins and ends at the same address.
This commit is contained in:
Jacob Young
2022-12-18 22:09:13 -05:00
parent 52e5c66025
commit 0e3feebb04
3 changed files with 30 additions and 9 deletions
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26
test/behavior/struct.zig
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@@ -1365,7 +1365,7 @@ test "fieldParentPtr of a zero-bit field" {
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
const S = struct {
fn testOneType(comptime A: type) !void {
fn testStruct(comptime A: type) !void {
{
const a = A{ .u = 0 };
const b_ptr = &a.b;
@@ -1379,9 +1379,29 @@ test "fieldParentPtr of a zero-bit field" {
try std.testing.expectEqual(&a, a_ptr);
}
}
fn testNestedStruct(comptime A: type) !void {
{
const a = A{ .u = 0 };
const c_ptr = &a.b.c;
const b_ptr = @fieldParentPtr(@TypeOf(a.b), "c", c_ptr);
try std.testing.expectEqual(&a.b, b_ptr);
const a_ptr = @fieldParentPtr(A, "b", b_ptr);
try std.testing.expectEqual(&a, a_ptr);
}
{
var a = A{ .u = 0 };
const c_ptr = &a.b.c;
const b_ptr = @fieldParentPtr(@TypeOf(a.b), "c", c_ptr);
try std.testing.expectEqual(&a.b, b_ptr);
const a_ptr = @fieldParentPtr(A, "b", b_ptr);
try std.testing.expectEqual(&a, a_ptr);
}
}
fn doTheTest() !void {
try testOneType(struct { b: void = {}, u: u8 });
try testOneType(struct { u: u8, b: void = {} });
try testStruct(struct { b: void = {}, u: u8 });
try testStruct(struct { u: u8, b: void = {} });
try testNestedStruct(struct { b: struct { c: void = {} } = .{}, u: u8 });
try testNestedStruct(struct { u: u8, b: struct { c: void = {} } = .{} });
}
};
try S.doTheTest();