Detect forks

Some really stupid applications (Hey, vim, that means you!)
love to fork after initializing gtk/libcanberra. This is really
bad style. We however have to deal with this cleanly, so we try
to detect the forks making sure all our calls fail cleanly
after the fork.

1 files changed, 51 insertions, 0 deletions

diff --git a/src/fork-detect.c b/src/fork-detect.c
new file mode 100644
index 0000000..622037c
--- /dev/null
+++ b/src/fork-detect.c
@@ -0,0 +1,51 @@
+/***
+  This file is part of libcanberra.
+
+  Copyright 2009 Lennart Poettering
+
+  libcanberra is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License as
+  published by the Free Software Foundation, either version 2.1 of the
+  License, or (at your option) any later version.
+
+  libcanberra is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with libcanberra. If not, see
+  <http://www.gnu.org/licenses/>.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <unistd.h>
+#include <sys/types.h>
+
+#include "fork-detect.h"
+
+int ca_detect_fork(void) {
+    static volatile pid_t pid = (pid_t) -1;
+    pid_t v;
+
+    /* Some really stupid applications (Hey, vim, that means you!)
+     * love to fork after initializing gtk/libcanberra. This is really
+     * bad style. We however have to deal with this cleanly, so we try
+     * to detect the forks making sure all our calls fail cleanly
+     * after the fork. */
+
+    /* Ideally we'd use atomic operations here, but we don't have them
+     * and this is not exactly crucial, so we don't care */
+
+    v = pid;
+
+    if (v == getpid() || v == (pid_t) -1) {
+        pid = getpid();
+        return 0;
+    }
+
+    return 1;
+}