$ uname -a
Linux rathercry.corp.yahoo.com 2.6.9-11.EL #1 Fri May 20 18:17:57 EDT 2005 i686
i686 i386 GNU/Linux
$ g++ -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../gcc-4.0.1/configure --prefix=/exp/opt/gcc401
--enable-languages=c++
Thread model: posix
gcc version 4.0.1
$ cat main.cc
namespace z {
  class A {
  public:
    A(int);
    ~A();
  };
#ifdef _IMPL
  A::A(int) {}
  A::~A() {}
#endif
}
using namespace z;
int main() {
  A a(0), b(0);
}
$ g++ -Wall -O3 main.cc
main.cc: In function ‘int main()’:
main.cc:15: internal compiler error: Segmentation fault
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://gcc.gnu.org/bugs.html> for instructions.

/* g++ -Wall -O3 -D_IMPL main.cc
   compiles fine, and
   g++ -Wall main.cc
   compiles fine, but linking complains about undefined A(int) and ~A(), as
expected.
*/

-- 
           Summary: internal compiler error
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: xiaoyi_wu at yahoo dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: Linux
  GCC host triplet: Linux
GCC target triplet: Linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23645