commit 0e3feebb042a538405153e4bc75a3bb73ee2e63c (tree)
parent 52e5c6602550788cab96957d1a177bc7952d7a09
Author: Jacob Young <jacobly0@users.noreply.github.com>
Date: Sun, 18 Dec 2022 22:09:13 -0500
codegen: fix taking the address of a zero-bit field in a zero-bit struct
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.
Diffstat:
3 files changed, 30 insertions(+), 9 deletions(-)
diff --git a/src/codegen/c.zig b/src/codegen/c.zig
@@ -5131,7 +5131,9 @@ fn structFieldPtr(f: *Function, inst: Air.Inst.Index, struct_ptr_ty: Type, struc
.begin, .end => {
try writer.writeByte('(');
try f.writeCValue(writer, struct_ptr, .Other);
- try writer.print(")[{}]", .{@boolToInt(field_loc == .end)});
+ try writer.print(")[{}]", .{
+ @boolToInt(field_loc == .end and struct_ty.hasRuntimeBitsIgnoreComptime()),
+ });
},
.field => |field| if (extra_name != .none) {
try f.writeCValueDerefMember(writer, struct_ptr, extra_name);
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
@@ -4046,9 +4046,8 @@ pub const DeclGen = struct {
break :blk parent_llvm_ty.constInBoundsGEP(parent_llvm_ptr, &indices, indices.len);
} else {
bitcast_needed = !parent_ty.eql(ptr_child_ty, dg.module);
- const indices: [1]*llvm.Value = .{
- llvm_u32.constInt(1, .False),
- };
+ const llvm_index = llvm_u32.constInt(@boolToInt(parent_ty.hasRuntimeBitsIgnoreComptime()), .False);
+ const indices: [1]*llvm.Value = .{llvm_index};
break :blk parent_llvm_ty.constInBoundsGEP(parent_llvm_ptr, &indices, indices.len);
}
},
@@ -9774,8 +9773,8 @@ pub const FuncGen = struct {
// end of the struct. Treat our struct pointer as an array of two and get
// the index to the element at index `1` to get a pointer to the end of
// the struct.
- const llvm_usize = try self.dg.lowerType(Type.usize);
- const llvm_index = llvm_usize.constInt(1, .False);
+ const llvm_u32 = self.dg.context.intType(32);
+ const llvm_index = llvm_u32.constInt(@boolToInt(struct_ty.hasRuntimeBitsIgnoreComptime()), .False);
const indices: [1]*llvm.Value = .{llvm_index};
return self.builder.buildInBoundsGEP(struct_llvm_ty, struct_ptr, &indices, indices.len, "");
}
diff --git a/test/behavior/struct.zig b/test/behavior/struct.zig
@@ -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();
