From b0f271d1db223b2cadd73e10258c48013d943691 Mon Sep 17 00:00:00 2001
From: Sebastian Huber <sebastian.huber@embedded-brains.de>
Date: Mon, 7 Aug 2017 07:35:19 +0200
Subject: [PATCH] Proper locking for getchar() and putchar()

Add internal inline functions _getchar_unlocked() and
_putchar_unlocked() if __CUSTOM_FILE_IO__ is not defined.  These
functions get _REENT only once.  Use them for getchar_unlocked() and
putchar_unlocked().  Define getchar() and putchar() to these unlocked
internal functions if __SINGLE_THREAD__ is defined, otherwise use the
external functions to use proper locking of the FILE object.

Assumes that __SINGLE_THREAD__ is not defined if __CYGWIN__ is defined.

Signed-off-by: Sebastian Huber <sebastian.huber@embedded-brains.de>
---
 newlib/libc/include/stdio.h | 39 ++++++++++++++++++++++++++++++-------
 1 file changed, 32 insertions(+), 7 deletions(-)

diff --git a/newlib/libc/include/stdio.h b/newlib/libc/include/stdio.h
index 1c32423d3..5d8cb1092 100644
--- a/newlib/libc/include/stdio.h
+++ b/newlib/libc/include/stdio.h
@@ -735,14 +735,37 @@ _ELIDABLE_INLINE int __sputc_r(struct _reent *_ptr, int _c, FILE *_p) {
 #define	fileno(p)	__sfileno(p)
 #endif
 
-#ifndef __CYGWIN__
-#ifndef lint
-#define	getc(fp)	__sgetc_r(_REENT, fp)
-#define putc(x, fp)	__sputc_r(_REENT, x, fp)
-#endif /* lint */
-#endif /* __CYGWIN__ */
+static __inline int
+_getchar_unlocked(void)
+{
+	struct _reent *_ptr;
+
+	_ptr = _REENT;
+	return (__sgetc_r(_ptr, _stdin_r(_ptr)));
+}
+
+static __inline int
+_putchar_unlocked(int _c)
+{
+	struct _reent *_ptr;
+
+	_ptr = _REENT;
+	return (__sputc_r(_ptr, _c, _stdout_r(_ptr)));
+}
+
+#ifdef __SINGLE_THREAD__
+#define	getc(_p)	__sgetc_r(_REENT, _p)
+#define	putc(_c, _p)	__sputc_r(_REENT, _c, _p)
+#define	getchar()	_getchar_unlocked()
+#define	putchar(_c)	_putchar_unlocked(_c)
+#endif /* __SINGLE_THREAD__ */
 #endif /* __cplusplus */
 
+#if __MISC_VISIBLE || __POSIX_VISIBLE
+#define	getchar_unlocked()	_getchar_unlocked()
+#define	putchar_unlocked(_c)	_putchar_unlocked(_c)
+#endif
+
 #if __MISC_VISIBLE
 /* fast always-buffered version, true iff error */
 #define	fast_putc(x,p) (--(p)->_w < 0 ? \
@@ -756,7 +779,7 @@ _ELIDABLE_INLINE int __sputc_r(struct _reent *_ptr, int _c, FILE *_p) {
 #define L_ctermid       16
 #endif
 
-#endif /* !__CUSTOM_FILE_IO__ */
+#else /* __CUSTOM_FILE_IO__ */
 
 #define	getchar()	getc(stdin)
 #define	putchar(x)	putc(x, stdout)
@@ -766,6 +789,8 @@ _ELIDABLE_INLINE int __sputc_r(struct _reent *_ptr, int _c, FILE *_p) {
 #define	putchar_unlocked(x)	putc_unlocked(x, stdout)
 #endif
 
+#endif /* !__CUSTOM_FILE_IO__ */
+
 _END_STD_C
 
 #endif /* _STDIO_H_ */