[RFA]: Fix do_cleanups if oldchain is NULL

[Daniel Jacobowitz]

On Fri, Jan 02, 2004 at 11:06:49AM -0500, Andrew Cagney wrote:
> >I recently solved a bug on the ia64 concerning cleanups.  What was 
> >happening was that a cleanup list was being re-initialized to NULL inside 
> >a loop and later do_cleanups() was called.  This caused the entire cleanup 
> >list to be run because the design is to run the list until the passed in 
> >cleanup is reached.  This caused other errors when the stream being used 
> >was deleted, etc...
> >
> >This patch adds a check to do_my_cleanups() so no cleanups will be 
> >performed if the passed in chain is NULL.
> >
> >Ok to commit?
> 
> (hmm, no one thought to review this while I was on hols :-()

Sorry, I was holding off on reviewing other people's patches during my vacation
so that I could catch up on my own.

> I think the bug is in the calling code, and not utils.c.  That patch 
> unfortunatly makes a fundamental change to the core of the cleanup code 
> and there's no easy way of demonstrating that other callers aren't 
> assuming that NULL implies do all cleanups.

How about making NULL an internal error then, as below?  I think we
should either do that or document its behavior, and it seems
accident-prone.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

2003-01-02  Daniel Jacobowitz  <drow@mvista.com>

	* utils.c (do_my_cleanups): Raise an internal error if the old_chain
	is NULL.

Index: utils.c
===================================================================
RCS file: /cvs/src/src/gdb/utils.c,v
retrieving revision 1.111
diff -u -p -r1.111 utils.c
--- utils.c	2 Jan 2004 17:35:01 -0000	1.111
+++ utils.c	2 Jan 2004 17:49:37 -0000
@@ -1,8 +1,8 @@
 /* General utility routines for GDB, the GNU debugger.
 
    Copyright 1986, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
-   1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003 Free Software
-   Foundation, Inc.
+   1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
+   Free Software Foundation, Inc.
 
    This file is part of GDB.
 
@@ -318,6 +318,11 @@ do_my_cleanups (struct cleanup **pmy_cha
 		struct cleanup *old_chain)
 {
   struct cleanup *ptr;
+
+  if (old_chain == NULL)
+    internal_error (__FILE__, __LINE__,
+		    "NULL chain passed to do_my_cleanups");
+
   while ((ptr = *pmy_chain) != old_chain)
     {
       *pmy_chain = ptr->next;	/* Do this first incase recursion */