Re: [PATCH v2] Use global stdio streams for all configurations

[Corinna Vinschen <vinschen@redhat.com>]

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.

Thx,
Corinna