gdb is great. Here's the .gdbinit file I have
for my current project:
printf "************** DEBUGGING nfsmount **************\n" printf "invoke simply as 'gdb', this file does the rest.\n" printf "it must be named gdb.ini on some systems, .gdbinit on others.\n" printf "i'm using a symlink to take care of both cases.\n" file nfsmount break cold break *cold+5 printf "to advance one instruction, type 'si'\n" printf "to do the same, but go through subroutine calls, type 'ni'\n" display/5i $pc display/x $esp display/x $ebp display/x $edi display/x $esi display/x $edx display/x $ecx display/x $ebx display/x $eax run
I'd forgotten all this shit. When you start running, the number at $esp
is the C language argc, and the words following are pointers
to the argv strings. Following that is a zero, then the environment strings,
again followed by a zero. How easy can it get? Here's an illustration,
after invoking gdb with the above .gdbinit:
(gdb) x/20x $esp 0xbffff7b0: 0x00000001 0xbffff8d9 0x00000000 0xbffff8fd 0xbffff7c0: 0xbffff944 0xbffff9b4 0xbffff9c8 0xbffff9e6 0xbffff7d0: 0xbffff9f1 0xbffffa01 0xbffffa39 0xbffffa48 0xbffff7e0: 0xbffffa60 0xbffffa86 0xbffffad0 0xbffffae8 0xbffff7f0: 0xbffffaf5 0xbffffb08 0xbffffcbb 0xbffffcc9 (gdb) x/s 0xbffff8d9 0xbffff8d9: "/home/jcomeau/src/nfsmount/nfsmount" (gdb) x/s 0xbffff8fd 0xbffff8fd: "CPLUS_INCLUDE_PATH=/usr/lib/qt-3.2.1/include:/usr/lib/qt-3.2.1/include" (gdb)
So what do we need the goddamned half-megabyte of glibc for? Linus Torvalds and Richard Stallman (and a cast of thousands) made it so easy to write apps in assembly! OK, so I'm joking a little here... but only a little.
last updated 2013-01-10 20:24:44. served from tektonic.jcomeau.com