I use the apple\'s gdb, version as follow
GNU gdb 6.3.50-20050815 (Apple version gdb-1344) (Fri Jul 3 01:19:56 UTC 2009)
Copyright 2004 Free Software Founda
http://gcc.gnu.org/gcc-4.5/changes.html says
GCC now generates unwind info also for epilogues. DWARF debuginfo generated by GCC now uses more features of DWARF3 than before, and also some DWARF4 features. GDB older than 7.0 is not able to handle either of these, so to debug GCC 4.5 generated binaries or libraries GDB 7.0 or later is needed. You can disable use of DWARF4 features with the
-gdwarf-3 -gstrict-dwarf
options, or use-gdwarf-2 -gstrict-dwarf
to restrict GCC to just DWARF2, but epilogue unwind info is emitted unconditionally whenever unwind info is emitted.
But you already knew that, because everyone reads the release notes when they upgrade their compiler, right?! ;-)