[PATCH v4 10/12] math: Handle fabsf128 !__USE_EXTERN_INLINES

[H.J. Lu]

On Mon, Nov 10, 2025 at 9:32 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> clang on x86_64 fails to build s_fabsf128.c with:

Please mention

This is one of the known clang limitation wrt inline function and
attribute definition,
where it does not allow to 'add' new attribute if a function is already defined:

> ../sysdeps/ieee754/float128/../ldbl-128/s_fabsl.c:32:1: error: attribute declaration must precede definition [-Werror,-Wignored-attributes]
>    32 | libm_alias_ldouble (__fabs, fabs)
>       | ^
> ../sysdeps/generic/libm-alias-ldouble.h:63:38: note: expanded from macro 'libm_alias_ldouble'
>    63 | #define libm_alias_ldouble(from, to) libm_alias_ldouble_r (from, to, )
>       |                                      ^
> ../sysdeps/ieee754/float128/float128_private.h:133:43: note: expanded from macro 'libm_alias_ldouble_r'
>   133 | #define libm_alias_ldouble_r(from, to, r) libm_alias_float128_r (from, to, r)
>       |                                           ^
> ../sysdeps/ieee754/float128/s_fabsf128.c:5:3: note: expanded from macro 'libm_alias_float128_r'
>     5 |   static_weak_alias (from ## f128 ## r, to ## f128 ## r);       \
>       |   ^
> ./../include/libc-symbols.h:166:46: note: expanded from macro 'static_weak_alias'
>   166 | #  define static_weak_alias(name, aliasname) weak_alias (name, aliasname)
>       |                                              ^
> ./../include/libc-symbols.h:154:38: note: expanded from macro 'weak_alias'
>   154 | # define weak_alias(name, aliasname) _weak_alias (name, aliasname)
>       |                                      ^
> ./../include/libc-symbols.h:156:52: note: expanded from macro '_weak_alias'
>   156 |   extern __typeof (name) aliasname __attribute__ ((weak, alias (#name))) \
>       |                                                    ^
> ../include/math.h:134:1: note: previous definition is here
>   134 | fabsf128 (_Float128 x)
>
> If compiler does not support __USE_EXTERN_INLINES we need to route
> fabsf128 call to an internal symbol.
> ---
>  include/math.h                        | 11 ++++++++---
>  sysdeps/ieee754/float128/s_fabsf128.c |  3 +++
>  2 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/include/math.h b/include/math.h
> index 84d44d44dc1..2565a4723ae 100644
> --- a/include/math.h
> +++ b/include/math.h
> @@ -114,9 +114,11 @@ __issignalingf (float x)
>
>  # if __HAVE_DISTINCT_FLOAT128
>
> +#  ifdef __USE_EXTERN_INLINES
> +
>  /* __builtin_isinf_sign is broken in GCC < 7 for float128.  */
> -#  if ! __GNUC_PREREQ (7, 0)
> -#   include <ieee754_float128.h>
> +#   if ! __GNUC_PREREQ (7, 0)
> +#    include <ieee754_float128.h>
>  extern inline int
>  __isinff128 (_Float128 x)
>  {
> @@ -126,13 +128,16 @@ __isinff128 (_Float128 x)
>    lx |= -lx;
>    return ~(lx >> 63) & (hx >> 62);
>  }
> -#  endif
> +#   endif
>
>  extern inline _Float128
>  fabsf128 (_Float128 x)
>  {
>    return __builtin_fabsf128 (x);
>  }
> +#  else
> +libm_hidden_proto (fabsf128)
> +#  endif
>  # endif
>
>
> diff --git a/sysdeps/ieee754/float128/s_fabsf128.c b/sysdeps/ieee754/float128/s_fabsf128.c
> index 2c1f277653e..9d64f150402 100644
> --- a/sysdeps/ieee754/float128/s_fabsf128.c
> +++ b/sysdeps/ieee754/float128/s_fabsf128.c
> @@ -6,3 +6,6 @@
>    libm_alias_float128_other_r (from, to, r)
>  #endif
>  #include "../ldbl-128/s_fabsl.c"
> +#ifndef __USE_EXTERN_INLINES
> +libm_hidden_def (fabsf128)
> +#endif
> --
> 2.43.0
>


-- 
H.J.