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authorJeff King <peff@peff.net>2009-01-22 01:02:35 -0500
committerJunio C Hamano <gitster@pobox.com>2009-01-21 22:46:52 -0800
commit4a16d072723b48699ea162da24eff05eba298834 (patch)
tree04d834214e8448f254118278ec057c77e3f8f1f1 /sigchain.c
parent479b0ae81c9291a8bb8d7b2347cc58eeaa701304 (diff)
downloadgit-4a16d072723b48699ea162da24eff05eba298834.tar.gz
chain kill signals for cleanup functions
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>
Diffstat (limited to 'sigchain.c')
-rw-r--r--sigchain.c43
1 files changed, 43 insertions, 0 deletions
diff --git a/sigchain.c b/sigchain.c
new file mode 100644
index 0000000000..a18d505e56
--- /dev/null
+++ b/sigchain.c
@@ -0,0 +1,43 @@
+#include "sigchain.h"
+#include "cache.h"
+
+#define SIGCHAIN_MAX_SIGNALS 32
+
+struct sigchain_signal {
+ sigchain_fun *old;
+ int n;
+ int alloc;
+};
+static struct sigchain_signal signals[SIGCHAIN_MAX_SIGNALS];
+
+static void check_signum(int sig)
+{
+ if (sig < 1 || sig >= SIGCHAIN_MAX_SIGNALS)
+ die("BUG: signal out of range: %d", sig);
+}
+
+int sigchain_push(int sig, sigchain_fun f)
+{
+ struct sigchain_signal *s = signals + sig;
+ check_signum(sig);
+
+ ALLOC_GROW(s->old, s->n + 1, s->alloc);
+ s->old[s->n] = signal(sig, f);
+ if (s->old[s->n] == SIG_ERR)
+ return -1;
+ s->n++;
+ return 0;
+}
+
+int sigchain_pop(int sig)
+{
+ struct sigchain_signal *s = signals + sig;
+ check_signum(sig);
+ if (s->n < 1)
+ return 0;
+
+ if (signal(sig, s->old[s->n - 1]) == SIG_ERR)
+ return -1;
+ s->n--;
+ return 0;
+}