Hi Ulrich,

Thanks for reporting things and the test case. I have attached a fix and 
added your test case to the test suite.

Thoughts ?
   Sami

On 06/24/2010 02:09 PM, Ulrich Weigand wrote:
> Hello,
>
> since one of this year's C++ namespace search related changes,
> GDB will go into an endless recursion and crash due to stack
> overflow when looking up symbols in the presence of a cycle
> in the "using" directive graph.
>
> For example, with the following test:
>
> namespace A
> {
>    namespace B
>      {
>        using namespace ::A;
>      }
>    using namespace B;
> }
>
> using namespace A;
>
> class test { };
> test x;
>
> int main() { }
>
> I'm seeing:
>
> (gdb) start
> Temporary breakpoint 1 at 0x80000626: file xxx.cc, line 16.
> Starting program: /home7/uweigand/fsf/gdb-head-build/gdb/a.out
>
> Temporary breakpoint 1, main () at xxx.cc:16
> 16      int main() { }
> (gdb) print x[0]
> Segmentation fault (core dumped)
>
> (The lookup that happens here is for operator[] -- which doesn't
> exist, but in trying to find it we run into the endless loop.)
>
> This is particularly annyoing as the SLES10 system library on
> s390 and ppc contains exactly this construct in the header
> /usr/include/c++/4.1.2/bits/localefwd.h:
>
> namespace std
> {
>    namespace __gnu_cxx_ldbl128
>      {
>        using namespace ::std;
>      }
>    using namespace __gnu_cxx_ldbl128 __attribute__((__strong__));
>
> which means it is present in just about every C++ executable.
>
> (This seems specific to the SLES backport of the long-double
> compatibility support.  The upstream implementation does not
> have this cycle ...  But still, the general construct looks
> to be valid C++ as far as I can tell.)
>
> Any thoughts how to fix this?
>
> Bye,
> Ulrich
>