Re: [PATCH 01/20] unlocked stdio extensions

[Yaakov Selkowitz <yselkowi at redhat dot com>]

Index: libc/stdio/clearerr.c
===================================================================
RCS file: /cvs/src/src/newlib/libc/stdio/clearerr.c,v
retrieving revision 1.6
diff -u -p -r1.6 clearerr.c
--- libc/stdio/clearerr.c	30 May 2012 08:58:41 -0000	1.6
+++ libc/stdio/clearerr.c	17 Dec 2014 18:26:40 -0000
@@ -17,20 +17,31 @@
 
 /*
 FUNCTION
-<<clearerr>>---clear file or stream error indicator
+<<clearerr>>, <<clearerr_unlocked>>---clear file or stream error indicator
 
 INDEX
 	clearerr
+INDEX
+	clearerr_unlocked
 
 ANSI_SYNOPSIS
 	#include <stdio.h>
 	void clearerr(FILE *<[fp]>);
 
+	#define _BSD_SOURCE
+	#include <stdio.h>
+	void clearerr_unlocked(FILE *<[fp]>);
+
 TRAD_SYNOPSIS
 	#include <stdio.h>
 	void clearerr(<[fp]>)
 	FILE *<[fp]>;
 
+	#define _BSD_SOURCE
+	#include <stdio.h>
+	void clearerr_unlocked(<[fp]>)
+	FILE *<[fp]>;
+
 DESCRIPTION
 The <<stdio>> functions maintain an error indicator with each file
 pointer <[fp]>, to record whether any read or write errors have
@@ -42,6 +53,14 @@ Use <<clearerr>> to reset both of these 
 
 See <<ferror>> and <<feof>> to query the two indicators.
 
+<<clearerr_unlocked>> is a non-thread-safe version of <<clearerr>>.
+<<clearerr_unlocked>> may only safely be used within a scope
+protected by flockfile() (or ftrylockfile()) and funlockfile().  This
+function may safely be used in a multi-threaded program if and only
+if they are called while the invoking thread owns the (FILE *)
+object, as is the case after a successful call to the flockfile() or
+ftrylockfile() functions.  If threads are disabled, then
+<<clearerr_unlocked>> is equivalent to <<clearerr>>.
 
 RETURNS
 <<clearerr>> does not return a result.
@@ -49,6 +68,8 @@ RETURNS
 PORTABILITY
 ANSI C requires <<clearerr>>.
 
+<<clearerr_unlocked>> is a BSD extension also provided by GNU libc.
+
 No supporting OS subroutines are required.
 */
 
Index: libc/stdio/clearerr_u.c
===================================================================
RCS file: libc/stdio/clearerr_u.c
diff -N libc/stdio/clearerr_u.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ libc/stdio/clearerr_u.c	17 Dec 2014 18:26:40 -0000
@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2014 Red Hat, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <_ansi.h>
+#include <stdio.h>
+#include "local.h"
+
+/* A subroutine version of the macro clearerr_unlocked.  */
+
+#undef	clearerr_unlocked
+
+_VOID
+_DEFUN(clearerr_unlocked, (fp),
+       FILE * fp)
+{
+  CHECK_INIT(_REENT, fp);
+  __sclearerr (fp);
+}