Debugging Firefox

[Andreas Gustafsson <gson%gson.org@localhost>]

Hi all,

I'm trying to run Firefox under gdb on NetBSD 7.0/amd64, but I'm not
having much luck.

I found a set of instructions at

  https://wiki.netbsd.org/tutorials/pkgsrc/debugging_firefox/

but when I follow them, gdb behaves stranegly, like being unable to
set a breakpoint in main(), and getting SIGTRAPs seemingly at random:

  $ /usr/pkgsrc/www/firefox/work/build/dist/bin $ ./run-mozilla.sh -g ./firefox
  [...]
  (gdb) break main
  Breakpoint 1 at 0x11be0: file /usr/pkgsrc/www/firefox/work/firefox-45.0.1/browser/app/nsBrowserApp.cpp, line 287.
  (gdb) run
  Starting program: /usr/pkgsrc/www/firefox/work/build/dist/bin/firefox 
  Error in re-setting breakpoint 1: Cannot access memory at address 0x11be0
  Error in re-setting breakpoint 1: Cannot access memory at address 0x11be0

  Program received signal SIGTRAP, Trace/breakpoint trap.
  0x00007f7ff683c3ea in ?? ()
  (gdb) where
  #0  0x00007f7ff683c3ea in ?? ()
  #1  0x00007f7ff78070f7 in ?? ()
  #2  0x0000000100000246 in ?? ()
  #3  0x00007f7ff7b8c400 in ?? ()
  #4  0x00007f7fdebfec70 in ?? ()
  #5  0x00007f7fee031a32 in ?? ()
  #6  0x00000001ffffffff in ?? ()
  #7  0x00007f7ff7b4a400 in ?? ()
  #8  0x0001000100000012 in ?? ()
  #9  0x0000000000000000 in ?? ()

And if I try to attach gdb to a running Firefox process, gdb seems to
think I'm trying to debug ld.elf_so:

  (gdb) attach 25976 
  Attaching to program: /usr/pkg/bin/firefox, process 25976
  Reading symbols from /usr/libexec/ld.elf_so...(no debugging symbols found)...done.
  Loaded symbols for /usr/libexec/ld.elf_so
  0x00007f7ff689f65a in .rtld_start () from /usr/libexec/ld.elf_so
  (gdb) where 
  #0  0x00007f7ff689f65a in .rtld_start () from /usr/libexec/ld.elf_so
  #1  0x00007f7ff7808f2b in ?? ()
  #2  0x00007f7fc76ffb60 in ?? ()
  #3  0x00007f7fcd847a48 in ?? ()
  #4  0x00007f7fc76ffb40 in ?? ()
  #5  0x00007f7ff1d9a324 in ?? ()
  #6  0x0000000200000000 in ?? ()
  #7  0x00007f7ff5f8b4d8 in ?? ()
  #8  0x00000000c76ffbf0 in ?? ()
  #9  0x00007f7fcbd09360 in ?? ()
  #10 0x00007f7fc76ffba0 in ?? ()
  #11 0x00007f7fcc4bf7a0 in ?? ()
  #12 0x00007f7ffffeb118 in ?? ()
  #13 0x0000000000000000 in ?? ()

Any hints?
-- 
Andreas Gustafsson, gson%gson.org@localhost