[COMMITTED] stdlib: Adapt tst-stdbit-builtins.c _BitInt tests on clang

[Gabriel Ravier]

On 8/12/26 8:21 PM, Adhemerval Zanella wrote:
> Two issues with clang-23:
>
> 1. -std=gnu11 triggers warnings with the 'uwb' suffix due to
>     -Wc23-extensions being enabled by default.
>
> 2. an ICE with __builtin_stdc_bit_ceil with a non-constant
>     unsigned _BitInt(1) argument [1]
>
> This patch disables the warning for 1. and disables the affected
> stdc_bit_ceil tests for clang.
>
> [1] https://github.com/llvm/llvm-project/issues/214478
> ---
>   stdlib/tst-stdbit-builtins.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/stdlib/tst-stdbit-builtins.c b/stdlib/tst-stdbit-builtins.c
> index a0c83c6dc22..9236b8c1114 100644
> --- a/stdlib/tst-stdbit-builtins.c
> +++ b/stdlib/tst-stdbit-builtins.c
> @@ -19,6 +19,7 @@
>   #include <stdbit.h>
>   #include <limits.h>
>   #include <support/check.h>
> +#include <libc-diag.h>
>   
>   #if __glibc_has_builtin (__builtin_stdc_leading_zeros) \
>       && __glibc_has_builtin (__builtin_stdc_leading_ones) \
> @@ -512,6 +513,10 @@ do_test (void)
>     TEST_COMPARE (b, 14);
>   # ifdef BITINT_MAXWIDTH
>   #  if BITINT_MAXWIDTH >= 64
> +  /* clang with -std=gnu11 warns that '_BitInt' suffix for literals is a C23
> +     extension.  */
> +  DIAG_PUSH_NEEDS_COMMENT_CLANG;
> +  DIAG_IGNORE_NEEDS_COMMENT_CLANG (23, "-Wc23-extensions");
>     TEST_COMPARE (stdc_leading_zeros (0uwb), 1);
>     TEST_COMPARE (expr_has_type (stdc_leading_zeros (0uwb), ui), 1);
>     TEST_COMPARE (stdc_leading_zeros (1uwb), 0);
> @@ -568,6 +573,10 @@ do_test (void)
>     TEST_COMPARE (expr_has_type (stdc_bit_ceil (0uwb), unsigned _BitInt(1)), 1);
>     TEST_COMPARE (stdc_bit_ceil (1uwb), 1);
>     TEST_COMPARE (expr_has_type (stdc_bit_ceil (1uwb), unsigned _BitInt(1)), 1);
> +  DIAG_POP_NEEDS_COMMENT_CLANG;
> +  /* clang-23 triggers an ICE with __builtin_stdc_bit_ceil with a non-constant
> +     unsigned _BitInt(1).  */
> +#   ifdef __clang__
>     unsigned _BitInt(1) c = 0;
>     TEST_COMPARE (stdc_bit_floor (c++), 0);
>     TEST_COMPARE (c, 1);
> @@ -577,6 +586,7 @@ do_test (void)
>     TEST_COMPARE (c, 1);
>     TEST_COMPARE (stdc_bit_ceil (c++), 1);
>     TEST_COMPARE (c, 0);
> +#   endif
>   #  endif
>   #  if BITINT_MAXWIDTH >= 512
>     TEST_COMPARE (stdc_leading_zeros ((unsigned _BitInt(512)) 0), 512);


I am puzzled as to how exactly the ifdef works to prevent the ICE on 
Clang - shouldn't that ifdef __clang__ be ifndef __clang__ ?


(also, perhaps mildly unrelated but I noticed it while looking at the 
same file: is `TEST_COMPARE (stdc_bit_floor (((unsigned _BitInt(373)) 
512) << 242) != (((unsigned _BitInt(512)) 512) << 242), 0);` supposed to 
have the two sides be different widths ?)