Re: Mismatch between newlib and glibc regarding fileno

[Torbjorn SVENSSON <torbjorn.svensson@foss.st.com>]

On 2024-02-09 17:54, Corinna Vinschen wrote:
> On Feb  9 08:40, Andrew Pinski wrote:
>> On Fri, Feb 9, 2024 at 8:30 AM Torbjorn SVENSSON
>> <torbjorn.svensson@foss.st.com> wrote:
>>>
>>> Hi all,
>>>
>>> I've been trying to run tests for arm-none-eabi on GCC14 tree.
>>> What I've seen is that fileno() is not available. If you look though the
>>> header files, I see that this is guarded by __POSIX_VISIBLE and due to a
>>> recent change in the GCC testsuite (part of PR96395), they moved the
>>> test case to gcc/testsuite/c-c++-common/analyzer/fileno-1.c and then
>>> invoke it with g++ and -std=c++98. With this change, strict ANSI is
>>> defined, but not __POSIX_VISIBLE.
>>
>> Note the testcase failure is recorded as https://gcc.gnu.org/PR113278 .
>>
>>>
>>> If I run the same test on the native g++ tool in Ubuntu, I instead get
>>> that __USE_POSIX is set (the guard for fileno() in glibc), so this
>>> differs from the behavior noticed with newlib.
>>
>> That is also due to _GNU_SOURCE being defined for C++ for Linux/g++. I
>> think this is just a GCC testcase issue rather than something needing
>> to be fixed in newlib even.
> 
> Along these lines, note the Linux man page for fileno:
> 
>      STANDARDS
>         POSIX.1-2008.
> 
>      HISTORY
>        POSIX.1-2001.
> 
> and the feature test in GLibc's stdio.h:
> 
>      #ifdef  __USE_POSIX
>      /* Return the system file descriptor for STREAM.  */
>      extern int fileno (FILE *__stream) __THROW __wur;
>      #endif /* Use POSIX.  */
> 
> 
> Corinna
> 


Okay, so newlib is more restrictive than glibc on this topic.
I will prepare a patch for test cases in GCC with defining _POSIX_SOURCE 
  so that the test cases succeed for newlib.

Kind regards,
Torbjörn