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chain kill signals for cleanup functions

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If a piece of code wanted to do some cleanup before exiting
(e.g., cleaning up a lockfile or a tempfile), our usual
strategy was to install a signal handler that did something
like this:

  do_cleanup(); /* actual work */
  signal(signo, SIG_DFL); /* restore previous behavior */
  raise(signo); /* deliver signal, killing ourselves */

For a single handler, this works fine. However, if we want
to clean up two _different_ things, we run into a problem.
The most recently installed handler will run, but when it
removes itself as a handler, it doesn't put back the first
handler.

This patch introduces sigchain, a tiny library for handling
a stack of signal handlers. You sigchain_push each handler,
and use sigchain_pop to restore whoever was before you in
the stack.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King
2009-01-22 01:02:35 -05:00
committed by Junio C Hamano
parent 479b0ae81c
commit 4a16d07272
12 changed files with 125 additions and 19 deletions
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5
builtin-fetch.c
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@ -10,6 +10,7 @@
#include "transport.h"
#include "run-command.h"
#include "parse-options.h"
#include "sigchain.h"
static const char * const builtin_fetch_usage[] = {
"git fetch [options] [<repository> <refspec>...]",
@ -58,7 +59,7 @@ static void unlock_pack(void)
static void unlock_pack_on_signal(int signo)
{
unlock_pack();
signal(SIGINT, SIG_DFL);
sigchain_pop(signo);
raise(signo);
}
@ -672,7 +673,7 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
ref_nr = j;
}
signal(SIGINT, unlock_pack_on_signal);
sigchain_push(SIGINT, unlock_pack_on_signal);
atexit(unlock_pack);
exit_code = do_fetch(transport,
parse_fetch_refspec(ref_nr, refs), ref_nr);