From: Elias Naur <mail@eliasnaur.com>
Date: Wed, 31 Jul 2019 12:33:57 +0000 (+0200)
Subject: runtime: don't forward SIGPIPE on macOS
X-Git-Tag: go1.14beta1~1280
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=d56a86e01f2e771a4706f0a5cfbe2d87cd888f05;p=gostls13.git

runtime: don't forward SIGPIPE on macOS

macOS and iOS deliver SIGPIPE signals to the main thread and not
the thread that raised it by writing to a closed socket or pipe.

SIGPIPE signals can be suppressed for sockets with the SO_NOSIGPIPE
option, but there is no similar option for pipes. We have no other
choice but to never forward SIGPIPE on macOS.

Fixes #33384

Change-Id: Ice3de75b121f00006ee11c26d560e619536460be
Reviewed-on: https://go-review.googlesource.com/c/go/+/188297
Run-TryBot: Elias Naur <mail@eliasnaur.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
---

diff --git a/misc/cgo/testcarchive/testdata/main3.c b/misc/cgo/testcarchive/testdata/main3.c
index 60a16cf5fc..4d11d9ce4c 100644
--- a/misc/cgo/testcarchive/testdata/main3.c
+++ b/misc/cgo/testcarchive/testdata/main3.c
@@ -12,6 +12,7 @@
 #include <time.h>
 #include <sched.h>
 #include <unistd.h>
+#include <pthread.h>
 
 #include "libgo3.h"
 
@@ -51,11 +52,18 @@ static void init() {
 	}
 }
 
+static void *provokeSIGPIPE(void *arg) {
+	ProvokeSIGPIPE();
+	return NULL;
+}
+
 int main(int argc, char** argv) {
 	int verbose;
 	struct sigaction sa;
 	int i;
 	struct timespec ts;
+	int res;
+	pthread_t tid;
 
 	verbose = argc > 2;
 	setvbuf(stdout, NULL, _IONBF, 0);
@@ -68,6 +76,19 @@ int main(int argc, char** argv) {
 	// a non-default SIGPIPE handler before the runtime initializes.
 	ProvokeSIGPIPE();
 
+	// Test that SIGPIPE on a non-main thread is also handled by Go.
+	res = pthread_create(&tid, NULL, provokeSIGPIPE, NULL);
+	if (res != 0) {
+		fprintf(stderr, "pthread_create: %s\n", strerror(res));
+		exit(EXIT_FAILURE);
+	}
+
+	res = pthread_join(tid, NULL);
+	if (res != 0) {
+		fprintf(stderr, "pthread_join: %s\n", strerror(res));
+		exit(EXIT_FAILURE);
+	}
+
 	if (verbose) {
 		printf("calling sigaction\n");
 	}
diff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go
index ad51dc1800..436c18c126 100644
--- a/src/runtime/signal_unix.go
+++ b/src/runtime/signal_unix.go
@@ -636,6 +636,13 @@ func sigfwdgo(sig uint32, info *siginfo, ctx unsafe.Pointer) bool {
 		return true
 	}
 
+	// This function and its caller sigtrampgo assumes SIGPIPE is delivered on the
+	// originating thread. This property does not hold on macOS (golang.org/issue/33384),
+	// so we have no choice but to ignore SIGPIPE.
+	if GOOS == "darwin" && sig == _SIGPIPE {
+		return true
+	}
+
 	// If there is no handler to forward to, no need to forward.
 	if fwdFn == _SIG_DFL {
 		return false