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

[Volodymyr Medvid <vmedvid@riseup.net>]

On Fri, Jun 10, 2022 at 1:45 PM Corinna Vinschen <vinschen@redhat.com> 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.
>
> Thx,
> Corinna
>

Hi, I confirmed the memory leak reported as
https://sourceware.org/pipermail/newlib/2022/019558.html and
https://bugs.linaro.org/show_bug.cgi?id=5841 is no longer observed
with this patch - many thanks!