In case you weren't familiar with the emacs build process, it's
somewhat strange -- you actually build a program called temacs, which
is then run, much lisp code is loaded, and then the program basically
dumps core in an organized fashion, producing (in theory) a runnable
binary with the lisp code internals pre-loaded, more or less.  The
particular code you'll want to examine is src/unex*.c; there are
several, since the process is platform-specific.  In the meantime,
though, you can try running temacs (it'll be src/temacs in the build
tree); it should respond better to your debugging efforts.

chad