gdb 7.6 can take tens of seconds to resolve symbols in C++

[Constantine Sapuntzakis]

See http://sourceware.org/bugzilla/show_bug.cgi?id=15454
filed by me.

Reverting 677b1bf from the gdb git repository fixes the problem.

In this revision, gdb started searching the base classes for the symbol too. The algorithm seems to require optimization.

Meanwhile, the problem can be worked with a one-line diff that reverts the behavior to the pre-677b1bf. Attaching the patch

lsb_release -rd
Description: Ubuntu 13.04
Release: 13.04

gdb:
  Installed: 7.6~20130417-0ubuntu1
  Candidate: 7.6~20130417-0ubuntu1
  Version table:
 *** 7.6~20130417-0ubuntu1 0
        500 http://us.archive.ubuntu.com/ubuntu/ raring/main amd64 Packages
        100 /var/lib/dpkg/status

[Constantine Sapuntzakis (csapuntz)]

Created attachment 7020
breakpoint trace

It takes minutes for GDB to find a symbol (vol::content_lh_key in this case) defined in a global namespace unless I prefix the symbol with ::

It seems to search for vol in the namespaces of all classes that the current class inherits from. This is ok, but it seems to repeat the search on the same symbol many times over.

I ran gdb against gdb and capture a bunch of stack traces during the symbol lookup. The file is attached.

break cp_lookup_symbol_in_namespace
silent
bt 4
print "\n\n"
cont
end

[Constantine Sapuntzakis (csapuntz)]

The following diff works around the problem for me by disabling lookup in base classes:

--- gdb-7.6~20130417/gdb/cp-namespace.c 2013-03-18 02:20:02.000000000 -0700
+++ gdb-7.6-mine/gdb/cp-namespace.c 2013-05-09 22:32:17.907659782 -0700
@@ -808,9 +808,7 @@
        if (sym != NULL)
          return sym;

- /* If no matching symbols were found, try searching any
- base classes. */
- return find_symbol_in_baseclass (parent_type, nested_name, block);
+ return NULL;
       }

     case TYPE_CODE_FUNC:

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "Disable base class search" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]

[Brian Murray (brian-murray)]

doko - could you take a look at this?

[Keiths-x (keiths-x)]

Does this patch help at all?

http://sourceware.org/ml/gdb-patches/2013-05/msg01097.html

[Brian Murray (brian-murray)]

The changes referenced in the following bug probably fixed this issue:

https://sourceware.org/bugzilla/show_bug.cgi?id=15519