`modf` function was generalized and renamed to `modfGeneric`, `modf` and
`modff` provide the appropriate type while calling that function. The
unit tests were also generalized so they can be reused for different
float types.
Both `modf` and `modff` were tested after making these changes:
```
$ stage4/bin/zig build test-libc -Dlibc-test-path=<LIBC-TEST-PATH> -Dtest-filter=modf -fqemu -fwasmtime --summary line
Build Summary: 921/921 steps succeeded
```
```
stage4/bin/zig build test-libc -Dlibc-test-path=<LIBC-TEST-PATH> -Dtest-filter=modff -fqemu -fwasmtime --summary line
Build Summary: 369/369 steps succeeded
```
The behaviour regarding special cases differs between `libc` and Zig's
`stdlib` for `modf`, so the implementation couldn't be a straightforward
calling of `stdlib` function.
Other than the obvious documented differences, I also had problems with
the `INVALID` flag being raised while running `libc-test` suite on riscv
arch through qemu. The solution was to test if the argument is `NaN`,
and then return a quiet `NaN` if so.
Passing tests, that should include all the special cases to be wary of,
were also added.
Test results:
```
$ stage4/bin/zig build test-libc -Dlibc-test-path=<LIBC-TEST-PATH> -Dtest-filter=modf -fqemu -fwasmtime --summary line
Build Summary: 921/921 steps succeeded
```
The functions were sorted alphabetically for easier navigation, and less
confusion where to add a new one. The sorting of comptime exports was
done within the visual "blocks".
Since this is my first time contributing I wanted to keep it simple and I added just one function
I tested with
```bash
stage3/bin/zig build -p stage4 -Dno-lib -Dno-langref -Denable-llvm=true --search-prefix ~/repos/zig-boostrap/out/native-linux-musl-baseline/
stage4/bin/zig build test-libc -Dlibc-test-path=../libc-test -Dtest-target-filter=x86_64-linux-musl
```
and the tests passed.
I'm planning on doing more once I get the hang of it.
Co-authored-by: david <davidc.fried@gmail.com>
Reviewed-on: https://codeberg.org/ziglang/zig/pulls/30888
Reviewed-by: Andrew Kelley <andrew@ziglang.org>
Co-authored-by: Daggerfall-is-the-best-TES-game <daggerfall-is-the-best-tes-game@noreply.codeberg.org>
Co-committed-by: Daggerfall-is-the-best-TES-game <daggerfall-is-the-best-tes-game@noreply.codeberg.org>
mihael