common-main: call restore_sigpipe_to_default()

This is another safety/sanity setup that should be in force
everywhere, but which we only applied in git.c. This did
catch most cases, since even external commands are typically
run via "git ..." (and the restoration applies to
sub-processes, too). But there were cases we missed, such as
somebody calling git-upload-pack directly via ssh, or
scripts which use dashed external commands directly.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/common-main.c b/common-main.c
index 353c6ea..20e55ef 100644
--- a/common-main.c
+++ b/common-main.c
@@ -1,6 +1,27 @@
 #include "cache.h"
 #include "exec_cmd.h"
 
+/*
+ * Many parts of Git have subprograms communicate via pipe, expect the
+ * upstream of a pipe to die with SIGPIPE when the downstream of a
+ * pipe does not need to read all that is written.  Some third-party
+ * programs that ignore or block SIGPIPE for their own reason forget
+ * to restore SIGPIPE handling to the default before spawning Git and
+ * break this carefully orchestrated machinery.
+ *
+ * Restore the way SIGPIPE is handled to default, which is what we
+ * expect.
+ */
+static void restore_sigpipe_to_default(void)
+{
+	sigset_t unblock;
+
+	sigemptyset(&unblock);
+	sigaddset(&unblock, SIGPIPE);
+	sigprocmask(SIG_UNBLOCK, &unblock, NULL);
+	signal(SIGPIPE, SIG_DFL);
+}
+
 int main(int argc, char **av)
 {
 	/*
@@ -18,5 +39,7 @@ int main(int argc, char **av)
 
 	argv[0] = git_extract_argv0_path(argv[0]);
 
+	restore_sigpipe_to_default();
+
 	return cmd_main(argc, argv);
 }