strerror_r: provide POSIX implementation

* libc/include/string.h (strerror_r): Update declaration.
* libc/string/strerror.c (strerror): Update documentation.
* libc/string/strerror_r.c (strerror_r): Always return
NUL-terminated string; don't overwrite too-short buf.
* libc/string/xpg_strerror_r.c (__xpg_strerror_r): Implement POSIX
variant.
* libc/string/Makefile.am (GENERAL_SOURCES): Build new file.
* libc/string/Makefile.in: Regenerate.

7 files changed, 115 insertions, 13 deletions

diff --git a/newlib/ChangeLog b/newlib/ChangeLog
index 8d500a371..e65008bee 100644
--- a/newlib/ChangeLog
+++ b/newlib/ChangeLog
@@ -1,3 +1,14 @@
+2011-02-09  Eric Blake  <eblake@redhat.com>
+
+	* libc/include/string.h (strerror_r): Update declaration.
+	* libc/string/strerror.c (strerror): Update documentation.
+	* libc/string/strerror_r.c (strerror_r): Always return
+	NUL-terminated string; don't overwrite too-short buf.
+	* libc/string/xpg_strerror_r.c (__xpg_strerror_r): Implement POSIX
+	variant.
+	* libc/string/Makefile.am (GENERAL_SOURCES): Build new file.
+	* libc/string/Makefile.in: Regenerate.
+
 2011-01-28  Corinna Vinschen  <vinschen@redhat.com>
 
 	* libc/stdio/fclose.c: Only use sfp lock to guard non-atomic
diff --git a/newlib/libc/include/string.h b/newlib/libc/include/string.h
index 547cddd84..7202b06ab 100644
--- a/newlib/libc/include/string.h
+++ b/newlib/libc/include/string.h
@@ -66,7 +66,20 @@ char 	*_EXFUN(strdup,(const char *));
 char 	*_EXFUN(_strdup_r,(struct _reent *, const char *));
 char 	*_EXFUN(strndup,(const char *, size_t));
 char 	*_EXFUN(_strndup_r,(struct _reent *, const char *, size_t));
-char 	*_EXFUN(strerror_r,(int, char *, size_t));
+/* There are two common strerror_r variants.  If you request
+   _GNU_SOURCE, you get the GNU version; otherwise you get the POSIX
+   version.  POSIX requires that #undef strerror_r will still let you
+   invoke the underlying function, but that requires gcc support.  */
+#ifdef _GNU_SOURCE
+char    *_EXFUN(strerror_r,(int, char *, size_t));
+#else
+# ifdef __GNUC__
+int      _EXFUN(strerror_r,(int, char *, size_t)) __asm__ ("__xpg_strerror_r");
+# else
+int      _EXFUN(__xpg_strerror_r,(int, char *, size_t));
+#  define strerror_r __xpg_strerror_r
+# endif
+#endif
 size_t	 _EXFUN(strlcat,(char *, const char *, size_t));
 size_t	 _EXFUN(strlcpy,(char *, const char *, size_t));
 int	 _EXFUN(strncasecmp,(const char *, const char *, size_t));
diff --git a/newlib/libc/string/Makefile.am b/newlib/libc/string/Makefile.am
index 82fec8be1..561d0e5a0 100644
--- a/newlib/libc/string/Makefile.am
+++ b/newlib/libc/string/Makefile.am
@@ -71,7 +71,8 @@ GENERAL_SOURCES = \
 	wmemcmp.c \
 	wmemcpy.c \
 	wmemmove.c \
-	wmemset.c
+	wmemset.c \
+	xpg_strerror_r.c
 
 if ELIX_LEVEL_1
 ELIX_2_SOURCES =
diff --git a/newlib/libc/string/Makefile.in b/newlib/libc/string/Makefile.in
index 6e0376b8c..a6e7e2e98 100644
--- a/newlib/libc/string/Makefile.in
+++ b/newlib/libc/string/Makefile.in
@@ -88,7 +88,7 @@ am__objects_1 = lib_a-bcopy.$(OBJEXT) lib_a-bzero.$(OBJEXT) \
 	lib_a-wcsxfrm.$(OBJEXT) lib_a-wcwidth.$(OBJEXT) \
 	lib_a-wmemchr.$(OBJEXT) lib_a-wmemcmp.$(OBJEXT) \
 	lib_a-wmemcpy.$(OBJEXT) lib_a-wmemmove.$(OBJEXT) \
-	lib_a-wmemset.$(OBJEXT)
+	lib_a-wmemset.$(OBJEXT) lib_a-xpg_strerror_r.$(OBJEXT)
 @ELIX_LEVEL_1_FALSE@am__objects_2 = lib_a-bcmp.$(OBJEXT) \
 @ELIX_LEVEL_1_FALSE@	lib_a-memccpy.$(OBJEXT) \
 @ELIX_LEVEL_1_FALSE@	lib_a-mempcpy.$(OBJEXT) \
@@ -120,7 +120,7 @@ am__objects_4 = bcopy.lo bzero.lo index.lo memchr.lo memcmp.lo \
 	wcslcpy.lo wcslen.lo wcsncat.lo wcsncmp.lo wcsncpy.lo \
 	wcsnlen.lo wcspbrk.lo wcsrchr.lo wcsspn.lo wcsstr.lo wcstok.lo \
 	wcswidth.lo wcsxfrm.lo wcwidth.lo wmemchr.lo wmemcmp.lo \
-	wmemcpy.lo wmemmove.lo wmemset.lo
+	wmemcpy.lo wmemmove.lo wmemset.lo xpg_strerror_r.lo
 @ELIX_LEVEL_1_FALSE@am__objects_5 = bcmp.lo memccpy.lo mempcpy.lo \
 @ELIX_LEVEL_1_FALSE@	stpcpy.lo stpncpy.lo strndup.lo \
 @ELIX_LEVEL_1_FALSE@	strcasestr.lo strndup_r.lo wcpcpy.lo \
@@ -215,6 +215,7 @@ MKDIR_P = @MKDIR_P@
 NEWLIB_CFLAGS = @NEWLIB_CFLAGS@
 NM = @NM@
 NMEDIT = @NMEDIT@
+NO_INCLUDE_LIST = @NO_INCLUDE_LIST@
 OBJDUMP = @OBJDUMP@
 OBJEXT = @OBJEXT@
 OTOOL = @OTOOL@
@@ -363,7 +364,8 @@ GENERAL_SOURCES = \
 	wmemcmp.c \
 	wmemcpy.c \
 	wmemmove.c \
-	wmemset.c
+	wmemset.c \
+	xpg_strerror_r.c
 
 @ELIX_LEVEL_1_FALSE@ELIX_2_SOURCES = \
 @ELIX_LEVEL_1_FALSE@	bcmp.c \
@@ -887,6 +889,12 @@ lib_a-wmemset.o: wmemset.c
 lib_a-wmemset.obj: wmemset.c
 	$(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(lib_a_CFLAGS) $(CFLAGS) -c -o lib_a-wmemset.obj `if test -f 'wmemset.c'; then $(CYGPATH_W) 'wmemset.c'; else $(CYGPATH_W) '$(srcdir)/wmemset.c'; fi`
 
+lib_a-xpg_strerror_r.o: xpg_strerror_r.c
+	$(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(lib_a_CFLAGS) $(CFLAGS) -c -o lib_a-xpg_strerror_r.o `test -f 'xpg_strerror_r.c' || echo '$(srcdir)/'`xpg_strerror_r.c
+
+lib_a-xpg_strerror_r.obj: xpg_strerror_r.c
+	$(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(lib_a_CFLAGS) $(CFLAGS) -c -o lib_a-xpg_strerror_r.obj `if test -f 'xpg_strerror_r.c'; then $(CYGPATH_W) 'xpg_strerror_r.c'; else $(CYGPATH_W) '$(srcdir)/xpg_strerror_r.c'; fi`
+
 lib_a-bcmp.o: bcmp.c
 	$(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(lib_a_CFLAGS) $(CFLAGS) -c -o lib_a-bcmp.o `test -f 'bcmp.c' || echo '$(srcdir)/'`bcmp.c
 
diff --git a/newlib/libc/string/strerror.c b/newlib/libc/string/strerror.c
index 043763141..61e40ab7a 100644
--- a/newlib/libc/string/strerror.c
+++ b/newlib/libc/string/strerror.c
@@ -301,6 +301,17 @@ declares that subsequent calls to <<strerror>> may overwrite the
 result string; therefore portable code cannot depend on the reentrancy
 of this subroutine.
 
+Although this implementation of <<strerror>> guarantees a non-null
+result with a NUL-terminator, some implementations return <<NULL>>
+on failure.  Although POSIX allows <<strerror>> to set <<errno>>
+to EINVAL on failure, this implementation does not do so (unless
+you provide <<_user_strerror>>).
+
+POSIX recommends that unknown <[errnum]> result in a message
+including that value, however it is not a requirement and this
+implementation does not provide that information (unless you
+provide <<_user_strerror>>).
+
 This implementation of <<strerror>> provides for user-defined
 extensibility.  <<errno.h>> defines <[__ELASTERROR]>, which can be
 used as a base for user-defined error values.  If the user supplies a
@@ -313,6 +324,9 @@ character pointer.  If <[errnum]> is unknown to <<_user_strerror>>,
 <<_user_strerror>> returns <[NULL]>.  The default <<_user_strerror>>
 returns <[NULL]> for all input values.
 
+Note that <<_user_sterror>> must be thread-safe and not alter <<errno>>
+if <<strerror_r>> is to comply with POSIX.
+
 <<strerror>> requires no supporting OS subroutines.
 
 QUICKREF
diff --git a/newlib/libc/string/strerror_r.c b/newlib/libc/string/strerror_r.c
index be5358f3e..c2057b7f0 100644
--- a/newlib/libc/string/strerror_r.c
+++ b/newlib/libc/string/strerror_r.c
@@ -1,3 +1,4 @@
+/* GNU variant of strerror_r. */
 /*
 FUNCTION
 	<<strerror_r>>---convert error number to string and copy to buffer
@@ -7,7 +8,11 @@ INDEX
 
 ANSI_SYNOPSIS
 	#include <string.h>
+	#ifdef _GNU_SOURCE
 	char *strerror_r(int <[errnum]>, char *<[buffer]>, size_t <[n]>);
+	#else
+	int strerror_r(int <[errnum]>, char *<[buffer]>, size_t <[n]>);
+	#endif
 
 TRAD_SYNOPSIS
 	#include <string.h>
@@ -19,35 +24,60 @@ TRAD_SYNOPSIS
 DESCRIPTION
 <<strerror_r>> converts the error number <[errnum]> into a
 string and copies the result into the supplied <[buffer]> for
-a length up to <[n]>, including the NUL terminator. The value of 
-<[errnum]> is usually a copy of <<errno>>.  If <<errnum>> is not a known 
+a length up to <[n]>, including the NUL terminator. The value of
+<[errnum]> is usually a copy of <<errno>>.  If <<errnum>> is not a known
 error number, the result is the empty string.
 
 See <<strerror>> for how strings are mapped to <<errnum>>.
 
 RETURNS
-This function returns a pointer to a string.  Your application must
-not modify that string.
+There are two variants: the GNU version always returns a NUL-terminated
+string, which is <[buffer]> if all went well, but which is another
+pointer if <[n]> was too small (leaving <[buffer]> untouched).  If the
+return is not <[buffer]>, your application must not modify that string.
+The POSIX version returns 0 on success, <[EINVAL]> if <<errnum>> was not
+recognized, and <[ERANGE]> if <[n]> was too small.  The variant chosen
+depends on macros that you define before inclusion of <<string.h>>.
 
 PORTABILITY
-<<strerror_r>> is a GNU extension.
+<<strerror_r>> with a <[char *]> result is a GNU extension.
+<<strerror_r>> with an <[int]> result is required by POSIX 2001.
+This function is compliant only if <<_user_strerror>> is not provided,
+or if it is thread-safe and does not modify <<errno>>.
+
+POSIX states that the contents of <[buf]> are unspecified on error,
+although this implementation guarantees a NUL-terminated string for
+all except <[n]> of 0.
+
+POSIX recommends that unknown <[errnum]> result in a message including
+that value, however it is not a requirement and this implementation
+provides only an empty string (unless you provide <<_user_strerror>>).
+POSIX also recommends that unknown <[errnum]> fail with EINVAL even
+when providing such a message, however it is not a requirement and
+this implementation will return success if <<_user_strerror>> provided
+a non-empty alternate string.
 
 <<strerror_r>> requires no supporting OS subroutines.
 
 */
 
 #undef __STRICT_ANSI__
+#define _GNU_SOURCE
 #include <errno.h>
 #include <string.h>
+#undef strerror_r
 
+/* For backwards-compatible linking, this must be the GNU signature;
+   see xpg_strerror_r.c for the POSIX version.  */
 char *
 _DEFUN (strerror_r, (errnum, buffer, n),
 	int errnum _AND
 	char *buffer _AND
 	size_t n)
 {
-  char *error;
-  error = strerror (errnum);
+  char *error = strerror (errnum);
 
-  return strncpy (buffer, (const char *)error, n);
+  if (strlen (error) >= n)
+    return error;
+  return strcpy (buffer, error);
 }
diff --git a/newlib/libc/string/xpg_strerror_r.c b/newlib/libc/string/xpg_strerror_r.c
new file mode 100644
index 000000000..ce94bd8a4
--- /dev/null
+++ b/newlib/libc/string/xpg_strerror_r.c
@@ -0,0 +1,25 @@
+/* POSIX variant of strerror_r. */
+#undef __STRICT_ANSI__
+#include <errno.h>
+#include <string.h>
+
+int
+_DEFUN (__xpg_strerror_r, (errnum, buffer, n),
+	int errnum _AND
+	char *buffer _AND
+	size_t n)
+{
+  char *error;
+
+  if (!n)
+    return ERANGE;
+  error = strerror (errnum);
+  if (strlen (error) >= n)
+    {
+      memcpy (buffer, error, n - 1);
+      buffer[n - 1] = '\0';
+      return ERANGE;
+    }
+  strcpy (buffer, error);
+  return *error ? 0 : EINVAL;
+}