# HG changeset patch
# User Bruno Haible <bruno@clisp.org>
# Date 1148471331 0
# Node ID 7f5add7487dc78db7555efca9edc1e497f2b835f
# Parent  87a7e1a6aca2cb7ff6377a3233f740d33f2f831a
Be resilient about NULL pointer arguments.

diff --git a/lib/ChangeLog b/lib/ChangeLog
--- a/lib/ChangeLog
+++ b/lib/ChangeLog
@@ -1,3 +1,10 @@
+2006-05-24  Bruno Haible  <bruno@clisp.org>
+
+	* printf-args.c (printf_fetchargs): Turn NULL pointers for
+	TYPE_STRING and TYPE_WIDE_STRING into a non-NULL replacement.
+	Reported by Thorsten Maerz <torte@netztorte.de> via
+	Aaron Stone <aaron@serendipity.cx>.
+
 2006-05-19  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* nanosleep.c [HAVE_SYS_SELECT_H]: Include <sys/select.h>.
diff --git a/lib/printf-args.c b/lib/printf-args.c
--- a/lib/printf-args.c
+++ b/lib/printf-args.c
@@ -1,5 +1,5 @@
 /* Decomposed printf argument list.
-   Copyright (C) 1999, 2002-2003 Free Software Foundation, Inc.
+   Copyright (C) 1999, 2002-2003, 2006 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -84,10 +84,29 @@
 #endif
       case TYPE_STRING:
 	ap->a.a_string = va_arg (args, const char *);
+	/* A null pointer is an invalid argument for "%s", but in practice
+	   it occurs quite frequently in printf statements that produce
+	   debug output.  Use a fallback in this case.  */
+	if (ap->a.a_string == NULL)
+	  ap->a.a_string = "(NULL)";
 	break;
 #ifdef HAVE_WCHAR_T
       case TYPE_WIDE_STRING:
 	ap->a.a_wide_string = va_arg (args, const wchar_t *);
+	/* A null pointer is an invalid argument for "%ls", but in practice
+	   it occurs quite frequently in printf statements that produce
+	   debug output.  Use a fallback in this case.  */
+	if (ap->a.a_wide_string == NULL)
+	  {
+	    static const wchar_t wide_null_string[] =
+	      {
+		(wchar_t)'(',
+		(wchar_t)'N', (wchar_t)'U', (wchar_t)'L', (wchar_t)'L',
+		(wchar_t)')',
+		(wchar_t)0
+	      };
+	    ap->a.a_wide_string = wide_null_string;
+	  }
 	break;
 #endif
       case TYPE_POINTER: