[PATCH v2 08/11] Add stdio_exit_handler()

[Takashi Yano]

On Thu, 12 May 2022 14:11:40 +0200
Matthew Joyce wrote:
> From: Matt Joyce <matthew.joyce@embedded-brains.de>
> 
> Added a dedicated stdio exit handler to avoid using _GLOBAL_REENT
> in exit().
> ---
>  newlib/libc/include/sys/reent.h |  2 ++
>  newlib/libc/stdio/findfp.c      | 11 ++++++++++-
>  newlib/libc/stdlib/exit.c       |  5 +++--
>  winsup/cygwin/signal.cc         |  5 +++--
>  4 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/newlib/libc/include/sys/reent.h b/newlib/libc/include/sys/reent.h
> index 4b0d68610..067294dc7 100644
> --- a/newlib/libc/include/sys/reent.h
> +++ b/newlib/libc/include/sys/reent.h
> @@ -837,6 +837,8 @@ extern struct _reent *_impure_ptr __ATTRIBUTE_IMPURE_PTR__;
>  
>  extern struct _reent _impure_data __ATTRIBUTE_IMPURE_DATA__;
>  
> +extern void (*__stdio_exit_handler) (void);
> +
>  void _reclaim_reent (struct _reent *);
>  
>  /* #define _REENT_ONLY define this to get only reentrant routines */
> diff --git a/newlib/libc/stdio/findfp.c b/newlib/libc/stdio/findfp.c
> index 5b0402ac1..719886e27 100644
> --- a/newlib/libc/stdio/findfp.c
> +++ b/newlib/libc/stdio/findfp.c
> @@ -26,6 +26,8 @@
>  #include <sys/lock.h>
>  #include "local.h"
>  
> +void (*__stdio_exit_handler) (void);
> +
>  #if defined(_REENT_SMALL) && !defined(_REENT_GLOBAL_STDIO_STREAMS)
>  const struct __sFILE_fake __sf_fake_stdin =
>      {_NULL, 0, 0, 0, 0, {_NULL, 0}, 0, _NULL};
> @@ -153,6 +155,12 @@ sfmoreglue (struct _reent *d, int n)
>    return &g->glue;
>  }
>  
> +static void
> +stdio_exit_handler (void)
> +{
> +  (void) _fwalk_reent (_GLOBAL_REENT, CLEANUP_FILE);
> +}
> +
>  /*
>   * Find a free FILE for fopen et al.
>   */
> @@ -166,12 +174,13 @@ __sfp (struct _reent *d)
>  
>    _newlib_sfp_lock_start ();
>  
> -  if (_GLOBAL_REENT->__cleanup == NULL) {
> +  if (__stdio_exit_handler == NULL) {
>  #ifdef _REENT_GLOBAL_STDIO_STREAMS
>      _GLOBAL_REENT->__sglue._niobs = 3;
>      _GLOBAL_REENT->__sglue._iobs = &__sf[0];
>  #endif
>      __sinit (_GLOBAL_REENT);
> +    __stdio_exit_handler = stdio_exit_handler;
>    }
>  
>    for (g = &_GLOBAL_REENT->__sglue;; g = g->_next)
> diff --git a/newlib/libc/stdlib/exit.c b/newlib/libc/stdlib/exit.c
> index 3e618914e..9b7bd518b 100644
> --- a/newlib/libc/stdlib/exit.c
> +++ b/newlib/libc/stdlib/exit.c
> @@ -59,7 +59,8 @@ exit (int code)
>  #endif
>      __call_exitprocs (code, NULL);
>  
> -  if (_GLOBAL_REENT->__cleanup)
> -    (*_GLOBAL_REENT->__cleanup) (_GLOBAL_REENT);
> +  if (__stdio_exit_handler != NULL)
> +    (*__stdio_exit_handler) ();
> +
>    _exit (code);
>  }
> diff --git a/winsup/cygwin/signal.cc b/winsup/cygwin/signal.cc
> index 9b6c2509d..f5f2efdc7 100644
> --- a/winsup/cygwin/signal.cc
> +++ b/winsup/cygwin/signal.cc
> @@ -13,6 +13,7 @@ details. */
>  #include <stdlib.h>
>  #include <sys/cygwin.h>
>  #include <sys/signalfd.h>
> +#include <sys/reent.h> /* needed for __stdio_exit_handler declaration */
>  #include "pinfo.h"
>  #include "sigproc.h"
>  #include "cygtls.h"
> @@ -408,8 +409,8 @@ abort (void)
>    _my_tls.call_signal_handler (); /* Call any signal handler */
>  
>    /* Flush all streams as per SUSv2.  */
> -  if (_GLOBAL_REENT->__cleanup)
> -    _GLOBAL_REENT->__cleanup (_GLOBAL_REENT);
> +  if (__stdio_exit_handler != NULL)
> +    (*__stdio_exit_handler) ();
>    do_exit (SIGABRT);	/* signal handler didn't exit.  Goodbye. */
>  }
>  
> -- 
> 2.31.1
> 

After this commit, "ps | cat" outputs nothing in cygwin. However,
just "ps" and "ls | cat" works. "stdbuf -o 0 ps | cat" also works.

I am not sure this is the right thing, however, I found the following
patch solves the issue. It seems that initializing __stdio_exit_handler
is missing.

diff --git a/newlib/libc/stdio/findfp.c b/newlib/libc/stdio/findfp.c
index 19952d4e0..e759b5402 100644
--- a/newlib/libc/stdio/findfp.c
+++ b/newlib/libc/stdio/findfp.c
@@ -63,6 +63,8 @@ struct _glue __sglue = {NULL, 3, &_GLOBAL_REENT->__sf[0]};
 #endif
 #endif
 
+static void stdio_exit_handler (void);
+
 #if (defined (__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED))
 _NOINLINE_STATIC void
 #else
@@ -109,6 +111,11 @@ std (FILE *ptr,
   if (__stextmode (ptr->_file))
     ptr->_flags |= __SCLE;
 #endif
+
+  if (__stdio_exit_handler == NULL) {
+    __sinit (_GLOBAL_REENT);
+    __stdio_exit_handler = stdio_exit_handler;
+  }
 }
 
 static inline void

Could you please have a look?

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>