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libzigc: add llround, llroundf, llroundl #35936

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novara754 wants to merge 1 commit from novara754/zig:llround into master
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Implements llround, llroundf and llroundl for libzigc #30978 just like #35600.

Tested with:

$ ./build/stage3/bin/zig build -p stage4 -Denable-llvm -Dno-lib
$ ./stage4/bin/zig build test-c-abi -Dtest-target-filter=x86_64-linux --summary line --maxrss 18600000000
$ ./stage4/bin/zig build test-libc-nsz -Dlibc-test-path=../libc-test -Dtest-filter=llround --summary line
Implements llround, llroundf and llroundl for libzigc #30978 just like #35600. Tested with: ``` $ ./build/stage3/bin/zig build -p stage4 -Denable-llvm -Dno-lib $ ./stage4/bin/zig build test-c-abi -Dtest-target-filter=x86_64-linux --summary line --maxrss 18600000000 $ ./stage4/bin/zig build test-libc-nsz -Dlibc-test-path=../libc-test -Dtest-filter=llround --summary line ```

Looks like this didn't trigger the CI workflow for some reason. Please do a rebase on master and force push; that should hopefully get it going.

Looks like this didn't trigger the CI workflow for some reason. Please do a rebase on master and force push; that should hopefully get it going.
andrewrk force-pushed llround from 082903d0e8 to dfb3c54e24
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2026年06月28日 00:14:42 +02:00 Compare
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Looks like this didn't seem to work on all architectures, though I have to admit I'm at a loss as to why.
I assume its due to difference in architectures in regards to floating point exceptions.

Is this something that should be fixed in the implementations for llround or should Zig's @round built-in be modified to accommodate?

I'm not sure how to proceed and would love some pointers.

Looks like this didn't seem to work on all architectures, though I have to admit I'm at a loss as to why. I assume its due to difference in architectures in regards to floating point exceptions. Is this something that should be fixed in the implementations for `llround` or should Zig's `@round` built-in be modified to accommodate? I'm not sure how to proceed and would love some pointers.
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I believe the failing test runs are the only ones running test-libc-nsz - at least, after searching through some of the various builds, only the failing runs mention test-libc-nsz or libc-test-path. The significance of this is that the libc test suite examines a large number of edge cases for libc functions, including rounding mode and floating point exception flags. I expect that if other builds also ran this test suite, they would fail with the same errors - regardless of architecture.

It looks like you may need to implement floating point exception handling within the one-liner function implementations you’re adding. This open PR adds the machinery to do so within ziglibc, although I believe there are other examples of functions within ziglibc that force the compiler to generate machine code implementing the correct behaviour.

should Zig's @round built-in be modified to accommodate?

This can't be done at the moment, because neither the Zig compiler nor any of its backends have support for fenv operations.

I recommend that you run test-libc-nsz for yourself on your branch to identify the errors, and then add any fenv manipulation code necessary to pass the failing tests. This is probably easiest done by rebasing on top of the branch I shared above, which provides access to functions like feraiseexcept in Zig.

I believe the failing test runs are the only ones running test-libc-nsz - at least, after searching through some of [the various builds](https://codeberg.org/ziglang/zig/actions/runs/4847/jobs/2/attempt/2), only the failing runs mention `test-libc-nsz` or `libc-test-path`. The significance of this is that the [libc test suite](https://wiki.musl-libc.org/libc-test) examines a large number of edge cases for libc functions, including rounding mode and floating point exception flags. I expect that if other builds also ran this test suite, they would fail with the same errors - regardless of architecture. It looks like you may need to implement floating point exception handling within the one-liner function implementations you’re adding. [This open PR](https://codeberg.org/ziglang/zig/pulls/35623) adds the machinery to do so within ziglibc, although I believe there are other examples of functions within ziglibc that force the compiler to generate machine code implementing the correct behaviour. > should Zig's @round built-in be modified to accommodate? This can't be done at the moment, because neither the Zig compiler nor any of its backends have support for fenv operations. I recommend that you run `test-libc-nsz` for yourself on your branch to identify the errors, and then add any fenv manipulation code necessary to pass the failing tests. This is probably easiest done by rebasing on top of the branch I shared above, which provides access to functions like `feraiseexcept` in Zig.
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