Re: Prevent crashes using $arg0

[Daniel Jacobowitz <drow@false.org>]

On Tue, Feb 07, 2006 at 10:38:28PM +0200, Eli Zaretskii wrote:
> Is it possible to have $arg0 behave outside user-defined functions as
> any other convenience variable?  That is, can we have this response
> instead:
> 
>     (gdb) if 1 == 1
>      >print $arg0
>      >end
>     $1 = void
>     (gdb)
> 
> ?  If this is not too hard, it's cleaner, since it doesn't reserve the
> names of these variables globally.

Good idea.

> [Time passes...] Actually, I'm quite sure we should behave like I
> suggested, since we already do that without the if clause:
> 
>     (gdb) print $arg0
>     $1 = void
>     (gdb)

And let's test that too.

Does this look better?  Tested x86_64-pc-linux-gnu.

-- 
Daniel Jacobowitz
CodeSourcery

2006-02-20  Daniel Jacobowitz  <dan@codesourcery.com>

	* cli/cli-script.c (insert_args): Handle NULL user_args.

2006-02-20  Daniel Jacobowitz  <dan@codesourcery.com>

	* gdb.base/commands.exp (stray_arg0_test): New test.

Index: cli/cli-script.c
===================================================================
RCS file: /cvs/src/src/gdb/cli/cli-script.c,v
retrieving revision 1.32
diff -u -p -r1.32 cli-script.c
--- cli/cli-script.c	17 Dec 2005 22:40:17 -0000	1.32
+++ cli/cli-script.c	20 Feb 2006 16:00:50 -0000
@@ -1,8 +1,8 @@
 /* GDB CLI command scripting.
 
    Copyright (c) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
-   1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2004, 2005 Free
-   Software Foundation, Inc.
+   1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2004, 2005, 2006
+   Free Software Foundation, Inc.
 
    This file is part of GDB.
 
@@ -590,6 +590,11 @@ insert_args (char *line)
   char *p, *save_line, *new_line;
   unsigned len, i;
 
+  /* If we are not in a user-defined function, treat $argc, $arg0, et
+     cetera as normal convenience variables.  */
+  if (user_args == NULL)
+    return xstrdup (line);
+
   /* First we need to know how much memory to allocate for the new line.  */
   save_line = line;
   len = 0;
Index: testsuite/gdb.base/commands.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.base/commands.exp,v
retrieving revision 1.14
diff -u -p -r1.14 commands.exp
--- testsuite/gdb.base/commands.exp	7 Mar 2005 21:36:16 -0000	1.14
+++ testsuite/gdb.base/commands.exp	20 Feb 2006 16:00:50 -0000
@@ -1,5 +1,5 @@
 #   Copyright 1988, 1990, 1991, 1992, 1994, 1995, 1997, 1998, 1999, 2000,
-#   2001, 2002, 2003 Free Software Foundation, Inc.
+#   2001, 2002, 2003, 2005, 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
@@ -563,6 +563,26 @@ proc temporary_breakpoint_commands {} {
 	timeout { fail "(timeout) run factorial until temporary breakpoint" }
     }
 }
+
+# Test that GDB can handle $arg0 outside of user functions without
+# crashing.
+proc stray_arg0_test { } {
+    gdb_test "print \$arg0" \
+	"\\\$\[0-9\]* = void" \
+	"stray_arg0_test #1"
+
+    gdb_test "if 1 == 1\nprint \$arg0\nend" \
+	"\\\$\[0-9\]* = void" \
+	"stray_arg0_test #2"
+
+    gdb_test "print \$arg0 = 1" \
+	"\\\$\[0-9\]* = 1" \
+	"stray_arg0_test #3"
+
+    gdb_test "print \$arg0" \
+	"\\\$\[0-9\]* = 1" \
+	"stray_arg0_test #4"
+}
   
 gdbvar_simple_if_test
 gdbvar_simple_while_test
@@ -579,3 +599,4 @@ test_command_prompt_position
 deprecated_command_test
 bp_deleted_in_command_test
 temporary_breakpoint_commands
+stray_arg0_test