runtime: forward crashing signals to late handlers

CL 49590 made it possible for external signal handlers to catch
signals from a crashing Go process. This CL extends that support
to handlers registered after the Go runtime has initialized.

Updates #20392 (and possibly fix it).

Change-Id: I18eccd5e958a505f4d1782a7fc51c16bd3a4ff9c
Reviewed-on: https://go-review.googlesource.com/57291
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/src/runtime/testdata/testprogcgo/catchpanic.go b/src/runtime/testdata/testprogcgo/catchpanic.go
index f03b6d3ea3..55a606d1bc 100644
--- a/src/runtime/testdata/testprogcgo/catchpanic.go
+++ b/src/runtime/testdata/testprogcgo/catchpanic.go
@@ -17,17 +17,21 @@ static void abrthandler(int signum) {
 	}
 }
 
-static void __attribute__ ((constructor)) sigsetup(void) {
+void registerAbortHandler() {
 	struct sigaction act;
-
-	if (getenv("CGOCATCHPANIC_INSTALL_HANDLER") == NULL)
-		return;
 	memset(&act, 0, sizeof act);
 	act.sa_handler = abrthandler;
 	sigaction(SIGABRT, &act, NULL);
 }
+
+static void __attribute__ ((constructor)) sigsetup(void) {
+	if (getenv("CGOCATCHPANIC_EARLY_HANDLER") == NULL)
+		return;
+	registerAbortHandler();
+}
 */
 import "C"
+import "os"
 
 func init() {
 	register("CgoCatchPanic", CgoCatchPanic)
@@ -35,5 +39,8 @@ func init() {
 
 // Test that the SIGABRT raised by panic can be caught by an early signal handler.
 func CgoCatchPanic() {
+	if _, ok := os.LookupEnv("CGOCATCHPANIC_EARLY_HANDLER"); !ok {
+		C.registerAbortHandler()
+	}
 	panic("catch me")
 }