zig/doc/langref/test_comptime_shlExact_overflow.zig at master - mirrors/zig - "Borealis" Git by INX: Hosted by INX "Xenon".

mirrors/zig

mirror of https://codeberg.org/ziglang/zig.git synced 2025-12-06 05:44:20 +00:00

Justus Klausecker d0586da18e Sema: Improve comptime arithmetic undef handling

This commit expands on the foundations laid by https://github.com/ziglang/zig/pull/23177
and moves even more `Sema`-only functionality from `Value`
to `Sema.arith`. Specifically all shift and bitwise operations,
`@truncate`, `@bitReverse` and `@byteSwap` have been moved and
adapted to the new rules around `undefined`.

Especially the comptime shift operations have been basically
rewritten, fixing many open issues in the process.

New rules applied to operators:
* `<<`, `@shlExact`, `@shlWithOverflow`, `>>`, `@shrExact`: compile error if any operand is undef
* `<<|`, `~`, `^`, `@truncate`, `@bitReverse`, `@byteSwap`: return undef if any operand is undef
* `&`, `|`: Return undef if both operands are undef, turn undef into actual `0xAA` bytes otherwise

Additionally this commit canonicalizes the representation of
aggregates with all-undefined members in the `InternPool` by
disallowing them and enforcing the usage of a single typed
`undef` value instead. This reduces the amount of edge cases
and fixes a bunch of bugs related to partially undefined vecs.

List of operations directly affected by this patch:
* `<<`, `<<|`, `@shlExact`, `@shlWithOverflow`
* `>>`, `@shrExact`
* `&`, `|`, `~`, `^` and their atomic rmw + reduce pendants
* `@truncate`, `@bitReverse`, `@byteSwap`

2025-08-12 16:33:57 +02:00

6 lines

135 B

Zig

Raw Permalink Blame History

 comptime {
     const x = @shlExact(@as(u8, 0b01010101), 2);
     _ = x;
 }
 // test_error=overflow of integer type 'u8' with value '340'