Add global stdio streams support for reent small.

[Douglas <info at ourairquality dot org>]

The global stdio streams option did not appear to work with reent small
option, but these two options are both useful on a low memory system.

This seems to simplify the reent small code in this area when using the
global stdio streams option. The fake streams and some of the checking
is not longer necessary.

btw the __sf slot in the reent small struct _reent appears to be unused.
Could that be removed, or is it fill for backwards compatibility?

>From e9b22ff92b932570180cb02ebf43699fa2775a97 Mon Sep 17 00:00:00 2001
From: Our Air Quality <info@ourairquality.org>
Date: Wed, 28 Feb 2018 23:31:48 +1100
Subject: [PATCH] Add global stdio streams support for reent small.

---
 newlib/libc/include/sys/reent.h | 41 ++++++++++++++++++++++++++++++++++++++++-
 newlib/libc/stdio/findfp.c      | 10 ++++++++--
 newlib/libc/stdio/local.h       |  2 +-
 3 files changed, 49 insertions(+), 4 deletions(-)

diff --git a/newlib/libc/include/sys/reent.h b/newlib/libc/include/sys/reent.h
index 1ef226194..0f21c6884 100644
--- a/newlib/libc/include/sys/reent.h
+++ b/newlib/libc/include/sys/reent.h
@@ -144,7 +144,7 @@ struct __sbuf {
  * _ub._base!=NULL) and _up and _ur save the current values of _p and _r.
  */
 
-#ifdef _REENT_SMALL
+#if defined(_REENT_SMALL) && !defined(_REENT_GLOBAL_STDIO_STREAMS)
 /*
  * struct __sFILE_fake is the start of a struct __sFILE, with only the
  * minimal fields allocated.  In __sinit() we really allocate the 3
@@ -418,6 +418,43 @@ struct _reent
   char *_signal_buf;                    /* strsignal */
 };
 
+#ifdef _REENT_GLOBAL_STDIO_STREAMS
+extern __FILE __sf[3];
+
+# define _REENT_INIT(var) \
+  { 0, \
+    &__sf[0], \
+    &__sf[1], \
+    &__sf[2], \
+    0,   \
+    _NULL, \
+    0, \
+    0, \
+    _NULL, \
+    _NULL, \
+    _NULL, \
+    0, \
+    0, \
+    _NULL, \
+    _NULL, \
+    _NULL, \
+    _NULL, \
+    _NULL, \
+    _REENT_INIT_ATEXIT \
+    {_NULL, 0, _NULL}, \
+    _NULL, \
+    _NULL, \
+    _NULL \
+  }
+
+#define _REENT_INIT_PTR_ZEROED(var) \
+  { (var)->_stdin = &__sf[0]; \
+    (var)->_stdout = &__sf[1]; \
+    (var)->_stderr = &__sf[2]; \
+  }
+
+#else
+
 extern const struct __sFILE_fake __sf_fake_stdin;
 extern const struct __sFILE_fake __sf_fake_stdout;
 extern const struct __sFILE_fake __sf_fake_stderr;
@@ -454,6 +491,8 @@ extern const struct __sFILE_fake __sf_fake_stderr;
     (var)->_stderr = (__FILE *)&__sf_fake_stderr; \
   }
 
+#endif
+
 /* Only add assert() calls if we are specified to debug.  */
 #ifdef _REENT_CHECK_DEBUG
 #include <assert.h>
diff --git a/newlib/libc/stdio/findfp.c b/newlib/libc/stdio/findfp.c
index cf924536f..3c4af5b22 100644
--- a/newlib/libc/stdio/findfp.c
+++ b/newlib/libc/stdio/findfp.c
@@ -26,7 +26,7 @@
 #include <sys/lock.h>
 #include "local.h"
 
-#ifdef _REENT_SMALL
+#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};
 const struct __sFILE_fake __sf_fake_stdout =
@@ -73,7 +73,7 @@ std (FILE *ptr,
 #else /* _STDIO_CLOSE_STD_STREAMS */
   ptr->_close = NULL;
 #endif /* _STDIO_CLOSE_STD_STREAMS */
-#if !defined(__SINGLE_THREAD__) && !defined(_REENT_SMALL)
+#if !defined(__SINGLE_THREAD__) && !(defined(_REENT_SMALL) && !defined(_REENT_GLOBAL_STDIO_STREAMS))
   __lock_init_recursive (ptr->_lock);
   /*
    * #else
@@ -269,9 +269,15 @@ __sinit (struct _reent *s)
      __sinit if it's 0. */
   if (s == _GLOBAL_REENT)
     s->__sdidinit = 1;
+# ifndef _REENT_GLOBAL_STDIO_STREAMS
   s->_stdin = __sfp(s);
   s->_stdout = __sfp(s);
   s->_stderr = __sfp(s);
+# else
+  s->_stdin = &__sf[0];
+  s->_stdout = &__sf[1];
+  s->_stderr = &__sf[2];
+# endif
 #endif
 
 #ifdef _REENT_GLOBAL_STDIO_STREAMS
diff --git a/newlib/libc/stdio/local.h b/newlib/libc/stdio/local.h
index 5f56792de..c778c21ae 100644
--- a/newlib/libc/stdio/local.h
+++ b/newlib/libc/stdio/local.h
@@ -197,7 +197,7 @@ extern _READ_WRITE_RETURN_TYPE __swrite64 (struct _reent *, void *,
 
 /* Called by the main entry point fns to ensure stdio has been initialized.  */
 
-#ifdef _REENT_SMALL
+#if defined(_REENT_SMALL) && !defined(_REENT_GLOBAL_STDIO_STREAMS)
 #define CHECK_INIT(ptr, fp) \
   do								\
     {								\
-- 
2.14.3