GDB, the GNU Project debugger, allows you to see what is going on `inside' another program while it executes -- or what another program was doing at the moment it crashed.
config/ aout_gnu.h atof-ieee.c atof-vax.c bfin-aux.h bfin-defs.h bfin-lex.l bfin-parse.y e-crisaout.c e-criself.c e-i386aout.c e-i386coff.c e-i386elf.c e-mipsecoff.c e-mipself.c itbl-mips.h m68k-parse.h m68k-parse.y obj-aout.c obj-aout.h obj-coff.c obj-coff.h obj-ecoff.c obj-ecoff.h obj-elf.c obj-elf.h obj-evax.c obj-evax.h obj-multi.c obj-multi.h doc/ po/ testsuite/ CONTRIBUTORS COPYING ChangeLog ChangeLog-0001 ChangeLog-0203 ChangeLog-2004 ChangeLog-2005 ChangeLog-2006 ChangeLog-9295 ChangeLog-9697 ChangeLog-9899 MAINTAINERS Makefile.am Makefile.in NEWS README acinclude.m4 aclocal.m4 app.c as.c as.h asintl.h atof-generic.c bignum.h bit_fix.h cgen.c cgen.h cond.c config.in configure configure.in configure.tgt debug.c dep-in.sed depend.c dw2gencfi.c dw2gencfi.h dwarf2dbg.c dwarf2dbg.h ecoff.c ecoff.h ehopt.c emul-target.h emul.h expr.c expr.h flonum-copy.c flonum-konst.c flonum-mult.c flonum.h frags.c frags.h gdbinit.in hash.c hash.h input-file.c input-file.h input-scrub.c itbl-lex.h itbl-lex.l itbl-ops.c itbl-ops.h itbl-parse.y listing.c listing.h literal.c macro.c macro.h messages.c obj.h output-file.c output-file.h read.c read.h sb.c sb.h stabs.c stamp-h.in struc-symbol.h subsegs.c subsegs.h symbols.c symbols.h tc.h write.c write.h