Re: Adding isinfl() and isnanl()

On 2026-02-05 17:53, Joel Sherrill wrote:
> 
> 
> On Thu, Feb 5, 2026 at 9:28 AM Corinna Vinschen <[email protected] 
> <mailto:[email protected]>> wrote:
> 
>     On Feb  5 09:09, Joel Sherrill wrote:
>      > Hi
>      >
>      > math.h:123 has isinfl () and isnanl() as this:
>      >
>      > 123
>      > <https://sourceware.org/git?p=newlib-cygwin.git;a=blob;f=newlib/libc/
>     include/math.h;h=5e92d2662da145cabad51e5946051aa34e9092b6;hb=HEAD#l123
>     <https://sourceware.org/git?p=newlib-cygwin.git;a=blob;f=newlib/libc/
>     include/math.h;h=5e92d2662da145cabad51e5946051aa34e9092b6;hb=HEAD#l123>>
>      > #ifdef __CYGWIN__ /* not implemented in newlib yet */
>      > 124
>      > <https://sourceware.org/git?p=newlib-cygwin.git;a=blob;f=newlib/libc/
>     include/math.h;h=5e92d2662da145cabad51e5946051aa34e9092b6;hb=HEAD#l124
>     <https://sourceware.org/git?p=newlib-cygwin.git;a=blob;f=newlib/libc/
>     include/math.h;h=5e92d2662da145cabad51e5946051aa34e9092b6;hb=HEAD#l124>>
>      > extern int isinfl (long double);
>      > 125
>      > <https://sourceware.org/git?p=newlib-cygwin.git;a=blob;f=newlib/libc/
>     include/math.h;h=5e92d2662da145cabad51e5946051aa34e9092b6;hb=HEAD#l125
>     <https://sourceware.org/git?p=newlib-cygwin.git;a=blob;f=newlib/libc/
>     include/math.h;h=5e92d2662da145cabad51e5946051aa34e9092b6;hb=HEAD#l125>>
>      > extern int isnanl (long double);
>      > 126
>      > <https://sourceware.org/git?p=newlib-cygwin.git;a=blob;f=newlib/libc/
>     include/math.h;h=5e92d2662da145cabad51e5946051aa34e9092b6;hb=HEAD#l126
>     <https://sourceware.org/git?p=newlib-cygwin.git;a=blob;f=newlib/libc/
>     include/math.h;h=5e92d2662da145cabad51e5946051aa34e9092b6;hb=HEAD#l126>>
>      > #endif
>      >
>      > The winsup implementation has them as simple wrappers for the
>      > corresponding built-in functions such as __builtin_isinf_sign().
>      >
>      > If I copied the winsup/ implementation and put each in a new file
>      > in newlib/libm so they are always available, is that OK?
> 
>     Barring other problems, you should just move them out of winsup into
>     newlib.
> 
>      > If so, any suggestions on location inside libm for simple wrappers
>      > for the corresponding builtin?
> 
>     libm/common
> 
>      > What would the conditional guard need to be? Just Cygwin and RTEMS?
>      > or more?
> 
>     I think this would have to be target cpu dependent.
> 
>      > Anything I am missing?
> 
>     Is it a safe bet that these builtins are available as inline functions
>     on all supported target cpus and compilers?  Unimplemented builtins just
>     point to their corresponding C lib function, isn't it?

You can use __has_builtin since gcc 10:

	$ info cpp __has_builtin		# gcc 13.4 4.2.9

https://gcc.gnu.org/onlinedocs/gcc-13.4.0/cpp/_005f_005fhas_005fbuiltin.html

$ info gcc 'C Extensions' 'Other Builtins'	# gcc 13.4 6.59

https://gcc.gnu.org/onlinedocs/gcc-13.4.0/gcc/Other-Builtins.html

Two paras above builtin_alloca:
https://gcc.gnu.org/onlinedocs/gcc-13.4.0/gcc/Other-Builtins.html#index-_005f_005fbuiltin_005falloca

...
"GCC provides built-in versions of the ISO C99 floating-point comparison macros 
that avoid raising exceptions for unordered operands.
They have the same names as the standard macros ( ‘isgreater’, ‘isgreaterequal’,
‘isless’, ‘islessequal’, ‘islessgreater’, and ‘isunordered’) , with ‘__builtin_’ 
prefixed.
*We intend for a library implementor to be able to simply ‘#define’ each 
standard macro to its built-in equivalent.*
In the same fashion, GCC provides ‘fpclassify’, ‘isfinite’, ‘isinf_sign’, 
‘isnormal’ and ‘signbit’ built-ins used with ‘__builtin_’ prefixed.
The ‘isinf’ and ‘isnan’ built-in functions appear both with and without the 
‘__builtin_’ prefix.
With ‘-ffinite-math-only’ option the ‘isinf’ and ‘isnan’ built-in functions will 
always return 0."

> Thanks. This one comment makes me want to avoid doing this.
> 
> I can easily test the ~15 RTEMS architectures but that leaves a lot
> I can't easily check. I will see if the code using this can be done a different
> way. Suggestions on that?

Avoid target builtins?

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retrancher  but when there is no more to cut
                                 -- Antoine de Saint-Exupéry