Debugging a program that uses SIGINT with gdb

Question

I frequently work with PostgreSQL for debugging, and it uses SIGINT internally for some of its inter-backend signalling.

As a result when running certain backends under gdb execution tends to get interrupted a lot. One can use the signal command to make sure SIGINT is passed to the program and that it is not captured by gdb... but then gdb doesn't respond to control-C on the command line, since that sends SIGINT.

If you run:

handle SIGINT noprint nostop pass

gdb will complain

SIGINT is used by the debugger.
Are you sure you want to change it? (y or n) y

Is there any way to get gdb to use a different interrupt signal? Or any alternative method that'd let me have gdb ignore SIGINT?

(This isn't an issue for most PostgreSQL backend debugging, but it's a pain with background workers and autovacuum).

Answer 1

On UNIX-like systems, you can distinguish a tty-initiated SIGINT from one sent by kill by looking at the si_pid element in the siginfo struct. If the pid is 0, it came from a tty.

So you could do something like this:

catch signal SIGINT
commands
  if $_siginfo._sifields._kill.si_pid == 0
    print "Received SIGINT from tty"
  else
    printf "Received SIGINT from %d; continuing\n", $_siginfo._sifields._kill.si_pid
    signal SIGINT
  end
end