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.
doc/ hosts/ po/ COPYING ChangeLog ChangeLog-0001 ChangeLog-0203 ChangeLog-2004 ChangeLog-2005 ChangeLog-2006 ChangeLog-9193 ChangeLog-9495 ChangeLog-9697 ChangeLog-9899 MAINTAINERS Makefile.am Makefile.in PORTING README TODO acinclude.m4 aclocal.m4 aix386-core.c aix5ppc-core.c aout-adobe.c aout-arm.c aout-cris.c aout-ns32k.c aout-sparcle.c aout-target.h aout-tic30.c aout0.c aout32.c aout64.c aoutf1.h aoutx.h archive.c archive64.c archures.c armnetbsd.c bfd-in.h bfd-in2.h bfd.c bfd.m4 bfdio.c bfdwin.c binary.c bout.c cache.c cf-i386lynx.c cf-sparclynx.c cisco-core.c coff-alpha.c coff-apollo.c coff-arm.c coff-aux.c coff-go32.c coff-h8300.c coff-h8500.c coff-i386.c coff-i860.c coff-i960.c coff-ia64.c coff-m68k.c coff-m88k.c coff-maxq.c coff-mcore.c coff-mips.c coff-or32.c coff-pmac.c coff-ppc.c coff-rs6000.c coff-sh.c coff-sparc.c coff-stgo32.c coff-svm68k.c coff-tic30.c coff-tic4x.c coff-tic54x.c coff-tic80.c coff-u68k.c coff-w65.c coff-we32k.c coff-x86_64.c coff-z80.c coff-z8k.c coff64-rs6000.c coffcode.h coffgen.c cofflink.c coffswap.h config.bfd config.in configure configure.com configure.host configure.in corefile.c cpu-alpha.c cpu-arc.c cpu-arm.c cpu-avr.c cpu-bfin.c cpu-cr16c.c cpu-cris.c cpu-crx.c cpu-d10v.c cpu-d30v.c cpu-dlx.c cpu-fr30.c cpu-frv.c cpu-h8300.c cpu-h8500.c cpu-hppa.c cpu-i370.c cpu-i386.c cpu-i860.c cpu-i960.c cpu-ia64-opc.c cpu-ia64.c cpu-ip2k.c