[PATCH v2] Use global stdio streams for all configurations

[Sebastian Huber]

On 10.06.22 12:45, Corinna Vinschen wrote:
> On Jun  8 11:43, Sebastian Huber wrote:
>> The _REENT_GLOBAL_STDIO_STREAMS was introduced by commit
>> 668a4c8722090fffd10869dbb15b879651c1370d in 2017.  Since then it was enabled by
>> default for RTEMS.  Recently, the option was enabled for Cygwin which
>> previously used an alternative implementation to use global stdio streams.
>>
>> In Newlib, the stdio streams are defined to thread-specific pointers
>> _reent::_stdin, _reent::_stdout and _reent::_stderr.  If the option is disabled
>> (the default for most systems), then these pointers are initialized to
>> thread-specific FILE objects which use file descriptors 0, 1, and 2,
>> respectively.  There are at least three problems with this:
>>
>> (1) The thread-specific FILE objects are closed by _reclaim_reent().  This
>>      leads to problems with language run-time libraries that provide wrappers to
>>      the C/POSIX stdio streams (for example C++ and Ada), since they use the
>>      thread-specific FILE objects of the initialization thread.  In case the
>>      initialization thread is deleted, then they use freed memory.
>>
>> (2) Since thread-specific FILE objects are used with a common output device via
>>      file descriptors 0, 1 and 2, the locking at FILE object level cannot ensure
>>      atomicity of the output, e.g. a call to printf().
>>
>> (3) There are resource managment issues, see:
>>
>>      https://sourceware.org/pipermail/newlib/2022/019558.html
>>
>>      https://bugs.linaro.org/show_bug.cgi?id=5841
>>
>> This patch enables the _REENT_GLOBAL_STDIO_STREAMS behaviour for all Newlib
>> configurations and removes the option.  This removes a couple of #ifdef blocks.
>> ---
>> v2:
>>
>> * Add missing ';' to _REENT_INIT_PTR_ZEROED().
>>
>> * Rebase to Newlib master.
>>
>>   newlib/README                         |   6 --
>>   newlib/configure.ac                   |  10 +--
>>   newlib/libc/include/sys/config.h      |   7 --
>>   newlib/libc/include/sys/reent.h       | 118 +++-----------------------
>>   newlib/libc/reent/impure.c            |   6 --
>>   newlib/libc/reent/reent.c             |  20 -----
>>   newlib/libc/stdio/fcloseall.c         |   4 -
>>   newlib/libc/stdio/findfp.c            |  53 +-----------
>>   newlib/libc/stdio/local.h             |  17 ----
>>   winsup/cygwin/include/cygwin/config.h |   1 -
>>   10 files changed, 14 insertions(+), 228 deletions(-)
> LGTM together with your "Fix __fp_lock_all() and __fp_unlock_all()" patch.

Thanks for having a look at it. I am on holidays next week. Should I 
still check it in today?

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