This is the mail archive of the
gdb@sourceware.org
mailing list for the GDB project.
Re: gdb_assert when resetting breakpoints
- From: Kai Tietz <Kai dot Tietz at onevision dot com>
- To: gdb <gdb at sourceware dot org>
- Cc: Roland Schwingel <roland dot schwingel at onevision dot de>
- Date: Tue, 17 Mar 2009 11:24:25 +0100
- Subject: Re: gdb_assert when resetting breakpoints
gdb-owner@sourceware.org wrote on 10.03.2009 15:02:40:
> Hi...
>
> When using current gdb cvs head sources I encounter a gdb_assert() in
> breakpoint.c line 7451.
> This is in function breakpoint_re_set_one().
> Let me tell you what I am doing to get it (reproduceably). I am not a
> guru to gdb's internals so
> please forgive me if I conclude something wrong.
>
> I am having a mixed C and Objective C application. I am running on
> windows using GNUstep
> for my ObjC Foundation classes. GNUstep-base is a shared library loaded
> lazy.
> Due to the nature of this bug I assume that this will also appear on
> other platforms like linux
> (according to my analysis). So it is not windows specific.
>
> I start gdb and set a breakpoint to main() using "b main". Then I run my
> app using "r".
> A few seconds later I get the assert in breakpoint.c:7451
> gdb_assert(sals.nelts==1).
> When I debug into it sals.nelts == 2. The assert happens when the
> gnustep-base shared
> library was loaded.
>
> What has happenend: In breakpoint.c line 7417 you find:
> sals = decode_line_1 (&s, 1, (struct symtab *) NULL, 0, (char ***)
> NULL,not_found_ptr);
> s points to "main" at that moment as found in the breakpoint structure
> supplied to breakpoint_re_set_one().
>
> sals (returned from decode_line_1) contains 2 entries.
> Sals entry 0 points to the ObjectiveC METHOD main of the foundation base
> class NSThread
> (written in ObjC notation -[NSThread main]). This is a real ObjC
> baseclass not something
> from my own code. It has also nothing to do with an application's
> entrypoint. It also perfectly
> legal in ObjectiveC to name methods like C functions. They do not
collide.
> Sals entry 1 points to the function "main()" of my application. This is
> the entry which I think is
> the correct one to use here.
>
> Obviously decode_line_1 returns every symbol matching a certain string
> independant of
> its language. As far as I understand gdb at the moment this appears to
> be ok.
>
> So what is the correct behaviour here to fix this problem? I assume that
> there might be more
> areas of symbol duplicates that can occur not only main() vs -[NSThread
> main].
>
> Maybe the assert should be replaced by a loop over the sals entries
> matching the infos from the
> breakpoint structure passed to breakpoint_re_set_one() and the
> individual symtab entry of one
> sals entry by filename(?) matching?
>
> Thanks in advance for your help,
>
> Roland
>
>
Hi,
I prepared a patch for this issue, which should solve the described
problem of Roland.
Changelog:
2009-03-17 Kai Tietz <Kai.Tietz@onevision.com>
* breakpoint.c: take care about multiple breakpoints
possibilities when resetting breakpoints.
Is this patch ok for apply?
Cheers,
Kai
| (\_/) This is Bunny. Copy and paste Bunny
| (='.'=) into your signature to help him gain
| (")_(") world domination.
Patch:
Index: src/gdb/breakpoint.c
===================================================================
--- src.orig/gdb/breakpoint.c 2009-03-17 11:10:45.000000000 +0100
+++ src/gdb/breakpoint.c 2009-03-17 11:19:01.890880000 +0100
@@ -57,6 +57,7 @@
#include "top.h"
#include "wrapper.h"
#include "valprint.h"
+#include "filenames.h"
#include "mi/mi-common.h"
@@ -7392,6 +7393,7 @@
struct breakpoint *b = (struct breakpoint *) bint;
struct value *mark;
int i;
+ int sals_index = -1;
int not_found = 0;
int *not_found_ptr = ¬_found;
struct symtabs_and_lines sals = {};
@@ -7455,20 +7457,59 @@
if (not_found)
break;
- gdb_assert (sals.nelts == 1);
- resolve_sal_pc (&sals.sals[0]);
- if (b->condition_not_parsed && s && s[0])
+ /* If only one sals entry is found use it directly
+ elsewise cycle over all sals and match breakpoint
+ against all returned sals by checking filenames and
+ linenumbers. */
+ if (sals.nelts == 1)
+ sals_index = 0;
+ else
+ {
+ for (i=0;(i < sals.nelts) && (sals_index == -1);i++)
+ {
+ int symtab_linenum = sals.sals[i].line;
+ int bpoint_linenum = b->line_number;
+
+ if (symtab_linenum == bpoint_linenum)
+ {
+ struct symtab *s = sals.sals[i].symtab;
+
+ if (s)
+ {
+ const char *symtab_filename = s->filename;
+ const char *bpoint_filename = b->source_file;
+
+ if (symtab_filename)
+ symtab_filename = lbasename(symtab_filename);
+
+ if (bpoint_filename)
+ bpoint_filename = lbasename(bpoint_filename);
+
+ if (bpoint_filename && symtab_filename
+ &&
(FILENAME_CMP(bpoint_filename,symtab_filename)
+ == 0))
+ sals_index = i;
+ }
+ }
+ }
+ }
+ gdb_assert(sals_index != -1);
+ if (sals_index == -1)
+ break;
+
+ resolve_sal_pc (&sals.sals[sals_index]);
+ if (b->condition_not_parsed && s && s[sals_index])
{
char *cond_string = 0;
int thread = -1;
- find_condition_and_thread (s, sals.sals[0].pc,
+ find_condition_and_thread (s, sals.sals[sals_index].pc,
&cond_string, &thread);
if (cond_string)
b->cond_string = cond_string;
b->thread = thread;
b->condition_not_parsed = 0;
}
- expanded = expand_line_sal_maybe (sals.sals[0]);
+ expanded = expand_line_sal_maybe (sals.sals[sals_index]);
cleanups = make_cleanup (xfree, sals.sals);
update_breakpoint_locations (b, expanded);
do_cleanups (cleanups);