Getting gdb to save a list of breakpoints?

Question

OK, info break lists the breakpoints, but not in a format that would work well with reusing them using the --command as in this question. Does gdb have a method for dumping them into a file acceptable for input again? Sometimes in a debugging session, it is necessary to restart gdb after building up a set of breakpoints for testing.

Edit: the .gdbinit file has the same problem as --command. The info break command does not list commands, but rather a table for human consumption.

To elaborate, here is a sample from info break:

(gdb) info break
Num Type           Disp Enb Address    What
1   breakpoint     keep y   0x08048517 <foo::bar(void)+7>

Answer 1

Put your gdb commands and breakpoints in a .gdbinit file just as you might type them at the gdb> prompt, and gdb will automatically load and run them on startup. This is a per-directory file, so you can have different files for different projects.

Answer 2

You can use logging:

(gdb) b main
Breakpoint 1 at 0x8049329
(gdb) info break
Num     Type           Disp Enb Address    What
1       breakpoint     keep y   0x08049329 <main+16>
(gdb) set logging file breaks.txt
(gdb) set logging on
Copying output to breaks.txt.
(gdb) info break
Num     Type           Disp Enb Address    What
1       breakpoint     keep y   0x08049329 <main+16>
(gdb) q

The file breaks.txt now contains:

Num     Type           Disp Enb Address    What
1       breakpoint     keep y   0x08049329 <main+16>

Writing an awk script that transforms that into a format useful for the .gdbinit or a --command file is easy. Or you may even make the script emit separate --eval-command's to the gdb command line...

Adding this small macro to .gdbinit will help you do it:

# call with dump_breaks file.txt
define dump_breaks
    set logging file $arg0
    set logging redirect on
    set logging on
    info breakpoints
    set logging off
    set logging redirect off
end

Answer 3

The problem is that setting a breakpoint is context sensative. What if you have two static functions named foo? If you are already debugging one of the modules that defines foo, then gdb will assume you meant that one. But if you just dump "break foo" into a file and then read that file at start-up, it will not be clear which function foo you mean.

Answer 4

Extension to the answer from Johannes: you could automatically reformat the output of info break into a valid gdb command file:

.gdbinit:

define bsave
   shell rm -f brestore.txt
   set logging file brestore.txt
   set logging on
   info break
   set logging off
   # reformat on-the-fly to a valid gdb command file
   shell perl -n -e 'print "break $1\n" if /^\d+.+?(\S+)$/g' brestore.txt > brestore.gdb
end 
document bsave
  store actual breakpoints
end

Afterwards you have a valid commandfile in brestore.gdb

This worked for me when the application is compiled with -g.

EDIT: successfully tested with gdb v6.8 on Ubuntu Karmic.

Answer 5

An extension to anon's extension to Johannes' answer:

.gdbinit:

define bsave
    shell rm -f brestore.txt
    set logging file brestore.txt
    set logging on
    info break
    set logging off
    # reformat on-the-fly to a valid gdb command file
    shell perl -n -e 'print "break $1\n" if /^\d+.+?(\S+)$/g' brestore.txt > brestore.gdb
end 
document bsave
  store actual breakpoints
end

define brestore
  source brestore.gdb
end
document brestore
  restore breakpoints saved by bsave
end

With brestore you can then restore the breakpoints saved with bsave.

Answer 6

Any other ideas? I have got

warning: Current output protocol does not support redirection

after

set logging on

EDIT:

I know that question is "how to save a list of breakpoints", however I just discover, that with gdb we can simply set "saved in file" breakpoints by

gdb> source breakpoints.txt

where breakpoints.txt is file like this:

break main.cpp:25
break engine.cpp:465
break wheel.cpp:57

Answer 7

Perhaps this:

http://sourceware.org/gdb/current/onlinedocs/gdb/Save-Breakpoints.html

Answer 8

warning: Current output protocol does not support redirection

I also get this error/warning in GDB when trying to enable logging in TUI mode, however the logging seems to work when in "non-TUI" mode. So I leave TUI mode whenever I want to log someting. (Toggle back and forth into TUI mode with CTRL-X, CTRL-A).

Here's how I work:

1. start GDB (in normal mode)
2. enable logging: set logging on - now it should not complain.
3. toggle back/forth to TUI mode and do GDB stuff
4. whenver I want to log something (like a huge backtrace dump) - toggle to normal mode

Hope this helps, /M:o)

Answer 9

As of gdb 7.2 you can now use the save breakpoints command.

save breakpoints <filename>
  Save all current breakpoint definitions to a file suitable for use
  in a later debugging session.  To read the saved breakpoint
  definitions, use the `source' command.