Re: Crashes on w32 and debugging

[Jason Rumney <jasonr@gnu.org>]

Lennart Borgman (gmail) wrote:
> I looked in the documentation for how to start Emacs under gdb, but I 
> can't find anything about it in nt/INSTALL.

1. Rebuild emacs after configure --no-opt (with optimisations on, 
stepping through the code doesn't always act as you expect it, and some 
variables cannot be inspected). 

2. cd ${emacs}/src          (where ${emacs} is your checkout directory). 
This serves two purposes - it makes it easy for gdb to find the emacs 
sources, and it also loads the .gdbinit in that directory, which defines 
some useful functions for looking at Lisp variables and backtraces.

3. gdb oo/i386/emacs.exe

4. Set any breakpoints using "break function_name" or "break 
file.c:linenumber"

5. run -Q

6. After the breakpoint is hit, step over functions with "next"/"n", or 
step in with "step"/"s". Inspect C variables with "print VARIABLE", if 
it is a lisp variable, "pr" immediately after the print will print its 
lisp value. "bt" will get a backtrace, including the Lisp backtrace as 
well as C.