runtime: do not exit(2) if a Go built DLL receives a signal

Fixes #35965

Change-Id: I172501fc0b29595e59b058f6e30f31efe5f6d1f9
Reviewed-on: https://go-review.googlesource.com/c/go/+/211139
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

2 files changed, 60 insertions, 0 deletions

diff --git a/src/runtime/testdata/testwinlibsignal/dummy.go b/src/runtime/testdata/testwinlibsignal/dummy.go
new file mode 100644
index 0000000000..82dfd91c93
--- /dev/null
+++ b/src/runtime/testdata/testwinlibsignal/dummy.go
@@ -0,0 +1,10 @@
+// +build windows
+
+package main
+
+//export Dummy
+func Dummy() int {
+	return 42
+}
+
+func main() {}
diff --git a/src/runtime/testdata/testwinlibsignal/main.c b/src/runtime/testdata/testwinlibsignal/main.c
new file mode 100644
index 0000000000..1787fef3b9
--- /dev/null
+++ b/src/runtime/testdata/testwinlibsignal/main.c
@@ -0,0 +1,50 @@
+#include <windows.h>
+#include <stdio.h>
+
+HANDLE waitForCtrlBreakEvent;
+
+BOOL WINAPI CtrlHandler(DWORD fdwCtrlType)
+{
+    switch (fdwCtrlType)
+    {
+    case CTRL_BREAK_EVENT:
+        SetEvent(waitForCtrlBreakEvent);
+        return TRUE;
+    default:
+        return FALSE;
+    }
+}
+
+int main(void)
+{
+    waitForCtrlBreakEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+    if (!waitForCtrlBreakEvent) {
+        fprintf(stderr, "ERROR: Could not create event");
+        return 1;
+    }
+
+    if (!SetConsoleCtrlHandler(CtrlHandler, TRUE))
+    {
+        fprintf(stderr, "ERROR: Could not set control handler");
+        return 1;
+    }
+
+    // The library must be loaded after the SetConsoleCtrlHandler call
+    // so that the library handler registers after the main program.
+    // This way the library handler gets called first.
+    HMODULE dummyDll = LoadLibrary("dummy.dll");
+    if (!dummyDll) {
+        fprintf(stderr, "ERROR: Could not load dummy.dll");
+        return 1;
+    }
+
+    printf("ready\n");
+    fflush(stdout);
+
+    if (WaitForSingleObject(waitForCtrlBreakEvent, 5000) != WAIT_OBJECT_0) {
+        fprintf(stderr, "FAILURE: No signal received");
+        return 1;
+    }
+
+    return 0;
+}