From patchwork Thu Jan 20 18:11:21 2011
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Subject: [libfortran] PR46267 strerror() might not be thread-safe
Date: Thu, 20 Jan 2011 08:11:21 -0000
From: Janne Blomqvist <blomqvist.janne@gmail.com>
X-Patchwork-Id: 79746
Message-Id: <AANLkTik9-NJ93hozTxpgasrO=v=qJBJcTtW3zoNe23Jy@mail.gmail.com>
To: Fortran List <fortran@gcc.gnu.org>, GCC Patches <gcc-patches@gcc.gnu.org>

Hello,

POSIX does not require strerror() to be thread-safe (although some
implementations are), using it is thus a potential error in
libgfortran. The attached patch fixes this in the case that
strerror_r() is available; thanks to Jakub for the hint about
__builtin_classify_type.

Regtested on x86_64-unknown-linux-gnu, Ok for trunk?


diff --git a/libgfortran/configure.ac b/libgfortran/configure.ac
index 7b28f12..4f137e4 100644
--- a/libgfortran/configure.ac
+++ b/libgfortran/configure.ac
@@ -249,7 +249,7 @@ AC_CHECK_FUNCS(chdir strerror getlogin gethostname kill link symlink perror)
 AC_CHECK_FUNCS(sleep time ttyname signal alarm ctime clock access fork execl)
 AC_CHECK_FUNCS(wait setmode execvp pipe dup2 close fdopen strcasestr getrlimit)
 AC_CHECK_FUNCS(gettimeofday stat fstat lstat getpwuid vsnprintf dup getcwd)
-AC_CHECK_FUNCS(localtime_r gmtime_r)
+AC_CHECK_FUNCS(localtime_r gmtime_r strerror_r)
 
 # Check for glibc backtrace functions
 AC_CHECK_FUNCS(backtrace backtrace_symbols)
diff --git a/libgfortran/intrinsics/gerror.c b/libgfortran/intrinsics/gerror.c
index ccb5c3e..44873f9 100644
--- a/libgfortran/intrinsics/gerror.c
+++ b/libgfortran/intrinsics/gerror.c
@@ -45,14 +45,13 @@ PREFIX(gerror) (char * msg, gfc_charlen_type msg_len)
 
   memset (msg, ' ', msg_len); /* Blank the string.  */
 
-  p = strerror (errno);
+  p = gf_strerror (errno);
   if (p == NULL)
     return;
 
   p_len = strlen (p);
   if (msg_len < p_len)
-    memcpy (msg, p, msg_len);
-  else
-    memcpy (msg, p, p_len);
+    p_len = msg_len;
+  memcpy (msg, p, p_len);
 }
 #endif
diff --git a/libgfortran/io/unix.c b/libgfortran/io/unix.c
index fa64e20..b7eba0b 100644
--- a/libgfortran/io/unix.c
+++ b/libgfortran/io/unix.c
@@ -262,7 +262,7 @@ flush_if_preconnected (stream * s)
 const char *
 get_oserror (void)
 {
-  return strerror (errno);
+  return gf_strerror (errno);
 }
 
 
diff --git a/libgfortran/libgfortran.h b/libgfortran/libgfortran.h
index ac86492..d092a54 100644
--- a/libgfortran/libgfortran.h
+++ b/libgfortran/libgfortran.h
@@ -1,5 +1,6 @@
 /* Common declarations for all of libgfortran.
-   Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
+   Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
+   2011
    Free Software Foundation, Inc.
    Contributed by Paul Brook <paul@nowt.org>, and
    Andy Vaught <andy@xena.eas.asu.edu>
@@ -756,6 +757,9 @@ internal_proto(notify_std);
 extern notification notification_std(int);
 internal_proto(notification_std);
 
+extern char *gf_strerror (int);
+internal_proto(gf_strerror);
+
 /* fpu.c */
 
 extern void set_fpu (void);
diff --git a/libgfortran/runtime/error.c b/libgfortran/runtime/error.c
index 1baf9d3..a04f2c5 100644
--- a/libgfortran/runtime/error.c
+++ b/libgfortran/runtime/error.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2002, 2003, 2005, 2006, 2007, 2009, 2010
+/* Copyright (C) 2002, 2003, 2005, 2006, 2007, 2009, 2010, 2011
    Free Software Foundation, Inc.
    Contributed by Andy Vaught
 
@@ -141,6 +141,36 @@ gfc_xtoa (GFC_UINTEGER_LARGEST n, char *buffer, size_t len)
   return p;
 }
 
+
+/* Hopefully thread-safe wrapper for a strerror() style function.  */
+
+char *
+gf_strerror (int errnum)
+{
+#ifdef HAVE_STRERROR_R
+#define GF_STRERROR_R_MAXSZ 256
+  static __thread char msg[GF_STRERROR_R_MAXSZ];
+  /* TODO: How to prevent the compiler warning due to strerror_r of
+     the untaken branch having the wrong return type?  */
+  if (__builtin_classify_type (strerror_r (0, msg, 0)) == 5)
+    {
+      /* GNU strerror_r()  */
+      return strerror_r (errnum, msg, GF_STRERROR_R_MAXSZ);
+    }
+  else
+    {
+      /* POSIX strerror_r ()  */
+      strerror_r (errnum, msg, GF_STRERROR_R_MAXSZ);
+      return msg;
+    }
+#else
+  /* strerror () is not necessarily thread-safe, but should at least
+     be available everywhere.  */
+  return strerror (errnum);
+#endif
+}
+
+
 /* show_locus()-- Print a line number and filename describing where
  * something went wrong */