Files
zig/test/cases
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
..
2025-07-16 10:27:39 -07:00
2024-09-26 21:02:14 -07:00

Test Case Quick Reference

Use comments at the end of the file to indicate metadata about the test case. Here are examples of different kinds of tests:

Compile Error Test

If you want it to be run with zig test and match expected error messages:

// error
// is_test=true
//
// :4:13: error: 'try' outside function scope

Execution

This will do zig run on the code and expect exit code 0.

// run

Translate-c

If you want to test translating C code to Zig use translate-c:

// translate-c
// c_frontend=aro,clang
// target=x86_64-linux
//
// pub const foo = 1;
// pub const immediately_after_foo = 2;
//
// pub const somewhere_else_in_the_file = 3:

Run Translated C

If you want to test translating C code to Zig and then executing it use run-translated-c:

// run-translated-c
// c_frontend=aro,clang
// target=x86_64-linux
//
// Hello world!

Incremental Compilation

Make multiple files that have ".", and then an integer, before the ".zig" extension, like this:

hello.0.zig
hello.1.zig
hello.2.zig

Each file can be a different kind of test, such as expecting compile errors, or expecting to be run and exit(0). The test harness will use these to simulate incremental compilation.

At the time of writing there is no way to specify multiple files being changed as part of an update.

Subdirectories

Subdirectories do not have any semantic meaning but they can be used for organization since the test harness will recurse into them. The full directory path will be prepended as a prefix on the test case name.

Limiting which Backends and Targets are Tested

// run
// backend=stage2,llvm
// target=x86_64-linux,x86_64-macos

Possible backends are:

  • stage1: equivalent to -fstage1.
  • stage2: equivalent to passing -fno-stage1 -fno-LLVM.
  • llvm: equivalent to -fLLVM -fno-stage1.