[PATCH] Introduce _REENT_GLOBAL_STDIO_STREAMS

[Sebastian Huber]

In Newlib, the stdio streams are defined to thread-specific pointers
_reent::_stdin, _reent::_stdout and _reent::_stderr.  In case
_REENT_SMALL is not defined, then these pointers are initialized via
_REENT_INIT_PTR() or _REENT_INIT_PTR_ZEROED() to thread-specific FILE
objects provided via _reent::__sf[3].  There are two problems with this
(at least in case of RTEMS).

(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 (e.g.  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().

Introduce a new Newlib configuration option _REENT_GLOBAL_STDIO_STREAMS
to enable the use of global stdio FILE objects.  Use this option for RTEMS.

Signed-off-by: Sebastian Huber <sebastian.huber at embedded-brains.de>
---
 newlib/libc/include/sys/config.h |  1 +
 newlib/libc/include/sys/reent.h  | 21 +++++++++++++++------
 newlib/libc/stdio/findfp.c       |  6 ++++++
 3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/newlib/libc/include/sys/config.h b/newlib/libc/include/sys/config.h
index 555239f8b..ae8caff7b 100644
--- a/newlib/libc/include/sys/config.h
+++ b/newlib/libc/include/sys/config.h
@@ -238,6 +238,7 @@
 #define _READ_WRITE_RETURN_TYPE _ssize_t
 #define __DYNAMIC_REENT__
 #define _REENT_GLOBAL_ATEXIT
+#define _REENT_GLOBAL_STDIO_STREAMS
 #endif
 
 #ifndef __EXPORT
diff --git a/newlib/libc/include/sys/reent.h b/newlib/libc/include/sys/reent.h
index 8b67889ac..2a79ccc71 100644
--- a/newlib/libc/include/sys/reent.h
+++ b/newlib/libc/include/sys/reent.h
@@ -644,14 +644,23 @@ struct _reent
      of the above members (on the off chance that future binary compatibility
      would be broken otherwise).  */
   struct _glue __sglue;		/* root of glue chain */
+# ifndef _REENT_GLOBAL_STDIO_STREAMS
   __FILE __sf[3];  		/* first three file descriptors */
+# endif
 };
 
+#ifdef _REENT_GLOBAL_STDIO_STREAMS
+extern __FILE __sf[3];
+#define _REENT_STDIO_STREAM(var, index) &__sf[index]
+#else
+#define _REENT_STDIO_STREAM(var, index) &(var).__sf[index]
+#endif
+
 #define _REENT_INIT(var) \
   { 0, \
-    &(var).__sf[0], \
-    &(var).__sf[1], \
-    &(var).__sf[2], \
+    _REENT_STDIO_STREAM(var, 0), \
+    _REENT_STDIO_STREAM(var, 1), \
+    _REENT_STDIO_STREAM(var, 2), \
     0, \
     "", \
     0, \
@@ -696,9 +705,9 @@ struct _reent
   }
 
 #define _REENT_INIT_PTR_ZEROED(var) \
-  { (var)->_stdin = &(var)->__sf[0]; \
-    (var)->_stdout = &(var)->__sf[1]; \
-    (var)->_stderr = &(var)->__sf[2]; \
+  { (var)->_stdin = _REENT_STDIO_STREAM(var, 0); \
+    (var)->_stdout = _REENT_STDIO_STREAM(var, 1); \
+    (var)->_stderr = _REENT_STDIO_STREAM(var, 2); \
     (var)->_new._reent._rand_next = 1; \
     (var)->_new._reent._r48._seed[0] = _RAND48_SEED_0; \
     (var)->_new._reent._r48._seed[1] = _RAND48_SEED_1; \
diff --git a/newlib/libc/stdio/findfp.c b/newlib/libc/stdio/findfp.c
index 83d3dc558..886ca7cc6 100644
--- a/newlib/libc/stdio/findfp.c
+++ b/newlib/libc/stdio/findfp.c
@@ -35,6 +35,10 @@ const struct __sFILE_fake __sf_fake_stderr =
     {_NULL, 0, 0, 0, 0, {_NULL, 0}, 0, _NULL};
 #endif
 
+#ifdef _REENT_GLOBAL_STDIO_STREAMS
+__FILE __sf[3];
+#endif
+
 #if (defined (__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED))
 _NOINLINE_STATIC _VOID
 #else
@@ -221,8 +225,10 @@ _DEFUN(__sinit, (s),
 
   s->__sglue._next = NULL;
 #ifndef _REENT_SMALL
+# ifndef _REENT_GLOBAL_STDIO_STREAMS
   s->__sglue._niobs = 3;
   s->__sglue._iobs = &s->__sf[0];
+# endif
 #else
   s->__sglue._niobs = 0;
   s->__sglue._iobs = NULL;
-- 
2.12.3