PR 67414 Better diagnostics on backtrace failure, gf_strerror bugfix

2015-09-02  Janne Blomqvist  <jb@gcc.gnu.org>

	PR libfortran/67414
	* io/write.c (gfc_itoa): Move to runtime/string.c.
	* libgfortran.h (show_backtrace): Make arg bool.
	(gfc_itoa): New prototype.
	* runtime/backtrace.c (struct mystate): Change type of try_simple
	field, add in_signal_handler field.
	(error_callback): Print out error number, or if not in a signal
	handler, the error message.
	(show_backtrace): Change type of arg, change initialization of
	struct mystate.
	(backtrace): Call show_backtrace with correct arg type.
	* runtime/compile_options.c (backtrace_handler): Call with correct
	arg type.
	* runtime/error.c (sys_abort): Likewise.
	(gf_strerror): Handle newlocale() failure.
	* runtime/string.c (gfc_itoa): Function moved here from
	io/write.c.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@227404 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 89 insertions, 14 deletions

diff --git a/libgfortran/runtime/backtrace.c b/libgfortran/runtime/backtrace.c
index 0d7c1fcea22..12ad76aac12 100644
--- a/libgfortran/runtime/backtrace.c
+++ b/libgfortran/runtime/backtrace.c
@@ -26,6 +26,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 
 #include <string.h>
 #include <stdlib.h>
+#include <errno.h>
 
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
@@ -38,8 +39,9 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 /* Store our own state while backtracing.  */
 struct mystate
 {
-  int try_simple;
   int frame;
+  bool try_simple;
+  bool in_signal_handler;
 };
 
 
@@ -65,15 +67,35 @@ static void
 error_callback (void *data, const char *msg, int errnum)
 {
   struct mystate *state = (struct mystate *) data;
+#define ERRHDR "\nCould not print backtrace: "
+
   if (errnum < 0)
     {
-      state->try_simple = 1;
+      state->try_simple = true;
       return;
     }
-
-  estr_write ("\nSomething went wrong while printing the backtrace: ");
-  estr_write (msg);
-  estr_write ("\n");
+  else if (errnum == 0)
+    {
+      estr_write (ERRHDR);
+      estr_write (msg);
+      estr_write ("\n");
+    }
+  else
+    {
+      char errbuf[256];
+      if (state->in_signal_handler)
+	{
+	  estr_write (ERRHDR);
+	  estr_write (msg);
+	  estr_write (", errno: ");
+	  const char *p = gfc_itoa (errnum, errbuf, sizeof (errbuf));
+	  estr_write (p);
+	  estr_write ("\n");
+	}
+      else
+	st_printf (ERRHDR "%s: %s\n", msg,
+		  gf_strerror (errnum, errbuf, sizeof (errbuf)));
+    }
 }
 
 static int
@@ -110,10 +132,10 @@ full_callback (void *data, uintptr_t pc, const char *filename,
 /* Display the backtrace.  */
 
 void
-show_backtrace (int in_signal_handler)
+show_backtrace (bool in_signal_handler)
 {
   struct backtrace_state *lbstate;
-  struct mystate state = { 0, 0 };
+  struct mystate state = { 0, false, in_signal_handler };
  
   lbstate = backtrace_create_state (NULL, 1, error_callback, NULL);
 
@@ -147,6 +169,6 @@ export_proto (backtrace);
 void
 backtrace (void)
 {
-  show_backtrace (0);
+  show_backtrace (false);
 }
 
diff --git a/libgfortran/runtime/compile_options.c b/libgfortran/runtime/compile_options.c
index f44256b43b4..087c070d3de 100644
--- a/libgfortran/runtime/compile_options.c
+++ b/libgfortran/runtime/compile_options.c
@@ -126,7 +126,7 @@ backtrace_handler (int signum)
 
   show_signal (signum);
   estr_write ("\nBacktrace for this error:\n");
-  show_backtrace (1);
+  show_backtrace (true);
 
   /* Now reraise the signal.  We reactivate the signal's
      default handling, which is to terminate the process.
diff --git a/libgfortran/runtime/error.c b/libgfortran/runtime/error.c
index 9eb07645411..4aabe4a4a74 100644
--- a/libgfortran/runtime/error.c
+++ b/libgfortran/runtime/error.c
@@ -173,7 +173,7 @@ sys_abort (void)
       || (options.backtrace == -1 && compile_options.backtrace == 1))
     {
       estr_write ("\nProgram aborted. Backtrace:\n");
-      show_backtrace (0);
+      show_backtrace (false);
       signal (SIGABRT, SIG_DFL);
     }
 
@@ -221,8 +221,16 @@ gf_strerror (int errnum,
 #ifdef HAVE_STRERROR_L
   locale_t myloc = newlocale (LC_CTYPE_MASK | LC_MESSAGES_MASK, "",
 			      (locale_t) 0);
-  char *p = strerror_l (errnum, myloc);
-  freelocale (myloc);
+  char *p;
+  if (myloc)
+    {
+      p = strerror_l (errnum, myloc);
+      freelocale (myloc);
+    }
+  else
+    /* newlocale might fail e.g. due to running out of memory, fall
+       back to the simpler strerror.  */
+    p = strerror (errnum);
   return p;
 #elif defined(HAVE_STRERROR_R)
 #ifdef HAVE_USELOCALE
diff --git a/libgfortran/runtime/string.c b/libgfortran/runtime/string.c
index 3c339da22a4..5bd0f61928e 100644
--- a/libgfortran/runtime/string.c
+++ b/libgfortran/runtime/string.c
@@ -1,7 +1,7 @@
 /* Copyright (C) 2002-2015 Free Software Foundation, Inc.
    Contributed by Paul Brook
 
-This file is part of the GNU Fortran 95 runtime library (libgfortran).
+This file is part of the GNU Fortran runtime library (libgfortran).
 
 Libgfortran is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -167,3 +167,48 @@ find_option (st_parameter_common *cmp, const char *s1, gfc_charlen_type s1_len,
 
   return -1;
 }
+
+
+/* gfc_itoa()-- Integer to decimal conversion.
+   The itoa function is a widespread non-standard extension to
+   standard C, often declared in <stdlib.h>.  Even though the itoa
+   defined here is a static function we take care not to conflict with
+   any prior non-static declaration.  Hence the 'gfc_' prefix, which
+   is normally reserved for functions with external linkage.  Notably,
+   in contrast to the *printf() family of functions, this ought to be
+   async-signal-safe.  */
+
+const char *
+gfc_itoa (GFC_INTEGER_LARGEST n, char *buffer, size_t len)
+{
+  int negative;
+  char *p;
+  GFC_UINTEGER_LARGEST t;
+
+  if (len < GFC_ITOA_BUF_SIZE)
+    sys_abort ();
+
+  if (n == 0)
+    return "0";
+
+  negative = 0;
+  t = n;
+  if (n < 0)
+    {
+      negative = 1;
+      t = -n; /*must use unsigned to protect from overflow*/
+    }
+
+  p = buffer + GFC_ITOA_BUF_SIZE - 1;
+  *p = '\0';
+
+  while (t != 0)
+    {
+      *--p = '0' + (t % 10);
+      t /= 10;
+    }
+
+  if (negative)
+    *--p = '-';
+  return p;
+}