$ cat hello.c
#include <stdio.h>
int
main (void)
{
printf ("Hello, world!n");
}
$ gcc -g3 -DFOO -UFOO -DFOO=2 hello.c -o hello
$ gdb -ex start hello
GNU gdb 6.6.90.20070911-cvs
Copyright (C) 2007 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/l
icenses/gpl.html>
This is free software: you are free to change and
redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type
"show copying"
and "show warranty" for details.
This GDB was configured as "ia64-suse-linux"...
Using host libthread_db library
"/lib/libthread_db.so.1".
/cvs/branch/gdb/gdb/macrotab.c:127: internal-error:
macro_bcache_free: Assertion `! t->bcache' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n)
The comment in macro_define_object is apparently wrong,
especially the
first sentence in the second paragraph:
/* If we're redefining a symbol, and the existing key
would be
identical to our new key, then the splay_tree_insert
function
will try to delete the old definition. When the
definition is
living on an obstack, this isn't a happy thing.
Since this only happens in the presence of questionable
debug
info, we just ignore all definitions after the first.
The only
case I know of where this arises is in GCC's output
for
predefined macros, and all the definitions are the same
in that
case. */
Andreas.
--
Andreas Schwab, SuSE Labs, schwab suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg,
Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5
214B 8276 4ED5
"And now for something completely different."
|
Andreas Schwab <schwabsuse.de> writes:
> $ cat hello.c
> #include <stdio.h>
> int
> main (void)
> {
> printf ("Hello, world!n");
> }
> $ gcc -g3 -DFOO -UFOO -DFOO=2 hello.c -o hello
> $ gdb -ex start hello
> GNU gdb 6.6.90.20070911-cvs
> Copyright (C) 2007 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/l
icenses/gpl.html>
> This is free software: you are free to change and
redistribute it.
> There is NO WARRANTY, to the extent permitted by law.
Type "show copying"
> and "show warranty" for details.
> This GDB was configured as
"ia64-suse-linux"...
> Using host libthread_db library
"/lib/libthread_db.so.1".
> /cvs/branch/gdb/gdb/macrotab.c:127: internal-error:
macro_bcache_free: Assertion `! t->bcache' failed.
> A problem internal to GDB has been detected,
> further debugging may prove unreliable.
> Quit this debugging session? (y or n)
>
> The comment in macro_define_object is apparently wrong,
especially the
> first sentence in the second paragraph:
>
> /* If we're redefining a symbol, and the existing key
would be
> identical to our new key, then the
splay_tree_insert function
> will try to delete the old definition. When the
definition is
> living on an obstack, this isn't a happy thing.
>
> Since this only happens in the presence of
questionable debug
> info, we just ignore all definitions after the
first. The only
> case I know of where this arises is in GCC's
output for
> predefined macros, and all the definitions are the
same in that
> case. */
>
> Andreas.
Hi, Andreas. Thanks for the bug report. I've committed
the
following, which fixes the problem for me.
gdb/ChangeLog:
2007-09-21 Jim Blandy <jimbcodesourcery.com>
* macrotab.h (new_macro_table): Document that removing
information
from an obstack/bcache-managed macro table leaks memory.
* macrotab.c (macro_free, macro_bcache_free): Instead of
asserting
that data is never freed in obstack/bcache-managed macro
tables,
just leak the storage.
(macro_undef): If we're undefining a macro at exactly the
same
source location that we defined it, simply remove the
definition
altogether.
diff -r 77afe7ffac2f gdb/macrotab.c
--- a/gdb/macrotab.c Fri Sep 21 14:38:59 2007 -0700
+++ b/gdb/macrotab.c Fri Sep 21 17:32:52 2007 -0700
-87,8
+87,14 static void
static void
macro_free (void *object, struct macro_table *t)
{
- gdb_assert (! t->obstack);
- xfree (object);
+ if (t->obstack)
+ /* There are cases where we need to remove entries from
a macro
+ table, even when reading debugging information.
This should be
+ rare, and there's no easy way to free arbitrary data
from an
+ obstack, so we just leak it. */
+ ;
+ else
+ xfree (object);
}
-120,12
+126,18 macro_bcache_str (struct macro_table *t,
/* Free a possibly bcached object OBJ. That is, if the
macro table T
- has a bcache, it's an error; otherwise, xfree OBJ. */
+ has a bcache, do nothing; otherwise, xfree OBJ. */
static void
macro_bcache_free (struct macro_table *t, void *obj)
{
- gdb_assert (! t->bcache);
- xfree (obj);
+ if (t->bcache)
+ /* There are cases where we need to remove entries from
a macro
+ table, even when reading debugging information.
This should be
+ rare, and there's no easy way to free data from a
bcache, so we
+ just leak it. */
+ ;
+ else
+ xfree (obj);
}
-781,25
+793,39 macro_undef (struct macro_source_file *s
if (n)
{
- /* This function is the only place a macro's
end-of-scope
- location gets set to anything other than "end
of the
- compilation unit" (i.e., end_file is zero).
So if this macro
- already has its end-of-scope set, then we're
probably seeing
- a second #undefinition for the same #definition.
*/
struct macro_key *key = (struct macro_key *)
n->key;
- if (key->end_file)
+ /* If we're removing a definition at exactly the same
point that
+ we defined it, then just delete the entry
altogether. GCC
+ 4.1.2 will generate DWARF that says to do this if
you pass it
+ arguments like '-DFOO -UFOO -DFOO=2'. */
+ if (source == key->start_file
+ && line == key->start_line)
+ splay_tree_remove
(source->table->definitions, n->key);
+
+ else
{
- complaint (&symfile_complaints,
- _("macro '%s' is #undefined twice, at %s:%d and
%s:%d"), name,
- source->filename, line,
key->end_file->filename,
- key->end_line);
+ /* This function is the only place a macro's
end-of-scope
+ location gets set to anything other than
"end of the
+ compilation unit" (i.e., end_file is
zero). So if this
+ macro already has its end-of-scope set, then
we're
+ probably seeing a second #undefinition for the
same
+ #definition. */
+ if (key->end_file)
+ {
+ complaint (&symfile_complaints,
+ _("macro '%s' is #undefined
twice,"
+ " at %s:%d and
%s:%d"),
+ name,
+ source->filename, line,
+ key->end_file->filename,
key->end_line);
+ }
+
+ /* Whether or not we've seen a prior
#undefinition, wipe out
+ the old ending point, and make this the ending
point. */
+ key->end_file = source;
+ key->end_line = line;
}
-
- /* Whatever the case, wipe out the old ending point,
and
- make this the ending point. */
- key->end_file = source;
- key->end_line = line;
}
else
{
diff -r 77afe7ffac2f gdb/macrotab.h
--- a/gdb/macrotab.h Fri Sep 21 14:38:59 2007 -0700
+++ b/gdb/macrotab.h Fri Sep 21 17:32:52 2007 -0700
-152,15
+152,15 struct macro_source_file
amongst compilation units in an executable file; if
BCACHE is zero,
don't cache these things.
- Note that, if either OBSTACK or BCACHE are non-zero,
then you
- should only ever add information the macro table --- you
should
- never remove things from it. You'll get an error if you
try. At
- the moment, since we only provide obstacks and bcaches
for macro
- tables for symtabs, this restriction makes a nice sanity
check.
- Obstacks and bcaches are pretty much grow-only
structures anyway.
- However, if we find that it's occasionally useful to
delete things
- even from the symtab's tables, and the storage leak
isn't a
- problem, this restriction could be lifted. */
+ Note that, if either OBSTACK or BCACHE are non-zero,
then removing
+ information from the table may leak memory. Neither
obstacks nor
+ bcaches really allow you to remove information, so
although we can
+ update the data structure to record the change, we can't
free the
+ old data. At the moment, since we only provide obstacks
and
+ bcaches for macro tables for symtabs, this isn't a
problem; only
+ odd debugging information makes a definition and then
deletes it at
+ the same source location (although 'gcc -DFOO -UFOO
-DFOO=2' does
+ do that in GCC 4.1.2.). */
struct macro_table *new_macro_table (struct obstack
*obstack,
struct bcache
*bcache);
|
