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

[Adhemerval Zanella Netto]

On 10/11/25 22:51, H.J. Lu wrote:
> 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:

I changed to:

--
math: Handle fabsf128 !__USE_EXTERN_INLINES

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

clang on x86_64 fails to build s_fabsf128.c with:

../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.
--

Ok with this commit message change?> 
>> ../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
>>
> 
>