| author |  Matthew Lugg <mlugg@mlugg.co.uk> 2025-01-12 23:45:22+00:00 |
| committer | Matthew Lugg <mlugg@mlugg.co.uk> 2025-01-14 20:27:49+00:00 |
| log | 27274d4fdea8061d7afacbb2b179fd49fbaca125 |
| tree | c822f893fc11d549384a3ba3942aa280011b69b3 |
| parent | affe45b31f48d216a407f060c49df6bad82ad30c |
Type: `struct {}` does not have a well-defined layout
`Type.hasWellDefinedLayout` was in disagreement with pointer loading
logic about auto-layout structs with zero fields, `struct {}`. For
consistency, these types should not have a well-defined layout.
This is technically a breaking change.2 files changed, 12 insertions(+), 5 deletions(-)
src- test
- cases
- compile_errors
src/Type.zig+1-5
| ... | ... | @@ -723,11 +723,7 @@ pub fn hasWellDefinedLayout(ty: Type, zcu: *const Zcu) bool { |
| 723 | 723 | .generic_poison, |
| 724 | 724 | => false, |
| 725 | 725 | }, |
| 726 | .struct_type => { | |
| 727 | const struct_type = ip.loadStructType(ty.toIntern()); | |
| 728 | // Struct with no fields have a well-defined layout of no bits. | |
| 729 | return struct_type.layout != .auto or struct_type.field_types.len == 0; | |
| 730 | }, | |
| 726 | .struct_type => ip.loadStructType(ty.toIntern()).layout != .auto, | |
| 731 | 727 | .union_type => { |
| 732 | 728 | const union_type = ip.loadUnionType(ty.toIntern()); |
| 733 | 729 | return switch (union_type.flagsUnordered(ip).runtime_tag) { |
test/cases/compile_errors/dereference_bad_pointer_via_array_mul.zig created+11
| ... | ... | @@ -0,0 +1,11 @@ |
| 1 | const A = struct {}; | |
| 2 | const B = struct {}; | |
| 3 | comptime { | |
| 4 | const val: [1]A = .{.{}}; | |
| 5 | const ptr: *const [1]B = @ptrCast(&val); | |
| 6 | _ = ptr ** 2; | |
| 7 | } | |
| 8 | ||
| 9 | // error | |
| 10 | // | |
| 11 | // :6:9: error: comptime dereference requires '[1]tmp.B' to have a well-defined layout |