Re: [PATCH] Fix __fp_lock_all() and __fp_unlock_all()

On 19/05/2022 14:02, Corinna Vinschen wrote:
> On May 18 19:13, Sebastian Huber wrote:
>> For _REENT_GLOBAL_STDIO_STREAMS, lock/unlock all FILE objects.  In the
>> repository, this function is only used by Cygwin during process forks.  Since
>> Cygwin enabled _REENT_GLOBAL_STDIO_STREAMS recently, without this fix no FILE
>> object at all was locked.
>> ---
>>   newlib/libc/stdio/findfp.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/newlib/libc/stdio/findfp.c b/newlib/libc/stdio/findfp.c
>> index 6933ff1db..a39082387 100644
>> --- a/newlib/libc/stdio/findfp.c
>> +++ b/newlib/libc/stdio/findfp.c
>> @@ -333,6 +333,8 @@ __fp_lock_all (void)
>>   #ifndef _REENT_GLOBAL_STDIO_STREAMS
>>     ptr = _REENT;
>>     (void) _fwalk_sglue (ptr, __fp_lock, &ptr->__sglue);
>> +#else
>> +  (void) _fwalk_sglue (NULL, __fp_lock, &__sglue);
>>   #endif
> 
> The resulting __fp_lock_all/__fp_unlock_all functions look a bit weird
> to me, codewise. Counter-proposal:
> 
> diff --git a/newlib/libc/stdio/findfp.c b/newlib/libc/stdio/findfp.c
> index 118637a18f5b..ebfbf0976de5 100644
> --- a/newlib/libc/stdio/findfp.c
> +++ b/newlib/libc/stdio/findfp.c
> @@ -329,31 +329,24 @@ __fp_unlock (struct _reent * ptr __unused, FILE * fp)
>     return 0;
>   }
>   
> +#ifdef _REENT_GLOBAL_STDIO_STREAMS
> +# define _PTR NULL
> +# define _GLUE __sglue
> +#else
> +# define _PTR _REENT
> +# define _GLUE _PTR->__sglue
> +#endif
> +
>   void
>   __fp_lock_all (void)
>   {
> -#ifndef _REENT_GLOBAL_STDIO_STREAMS
> -  struct _reent *ptr;
> -#endif
> -
> -  __sfp_lock_acquire ();
> -
> -#ifndef _REENT_GLOBAL_STDIO_STREAMS
> -  ptr = _REENT;
> -  (void) _fwalk_sglue (ptr, __fp_lock, &ptr->__sglue);
> -#endif
> +  _fwalk_sglue (_PTR, __fp_lock, &_GLUE);
>   }
>   
>   void
>   __fp_unlock_all (void)
>   {
> -#ifndef _REENT_GLOBAL_STDIO_STREAMS
> -  struct _reent *ptr;
> -
> -  ptr = _REENT;
> -  (void) _fwalk_sglue (ptr, __fp_unlock, &ptr->__sglue);
> -#endif
> -
> +  _fwalk_sglue (_PTR, __fp_unlock, &_GLUE);
>     __sfp_lock_release ();
>   }
>   #endif
> 
> What do you think?

This patch was a preparation for this proposal:

https://sourceware.org/pipermail/newlib/2022/019735.html

It is a behaviour change for the default Newlib configuration, however, 
from my point of view it is more or less a bug fix.

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