Add cvar to disable native exe crash handling

So server owners who want to get Unix core dumps for native exe
gamelogic could set sgame.nativeExeCrashHandler to 0. Doing this stops
the crash handler from being installed. In case of a fatal C++ exception
we still install the terminate handler so we can log the exception
message, but afterward, if the cvar is off, we call abort() instead of
shutting down with the ErrorMsg IPC.

Author: slipher

cmake/DaemonGame.cmake

@@ -119,6 +119,9 @@ function(buildGameModule module_slug)
 		set_target_properties(${module_target} PROPERTIES PREFIX "")
 		set(GAMEMODULE_DEFINITIONS "${GAMEMODULE_DEFINITIONS};BUILD_VM_IN_PROCESS")
 	else()
+		if (module_slug STREQUAL "native-exe")
+			set(GAMEMODULE_DEFINITIONS "${GAMEMODULE_DEFINITIONS};BUILD_VM_NATIVE_EXE")
+		endif()
 		add_executable("${module_target}" ${module_target_args})
 	endif()
 

src/shared/CommonProxies.cpp

@@ -437,8 +437,17 @@ namespace VM {
 
     void InitializeProxies(int milliseconds) {
         baseTime = Sys::SteadyClock::now() - std::chrono::milliseconds(milliseconds);
-        Cmd::InitializeProxy();
         Cvar::InitializeProxy();
+
+#ifdef BUILD_VM_NATIVE_EXE
+        // Set up the crash handler now that we have cvars to know if we want to use it.
+        // The handler wouldn't have worked before StaticInitMsg anyway since it needs IPC to log anything.
+        if (useNativeExeCrashHandler.Get()) {
+            Sys::SetupCrashHandler();
+        }
+#endif
+
+        Cmd::InitializeProxy();
     }
 
     static void HandleMiscSyscall(int minor, Util::Reader& reader, IPC::Channel& channel) {

src/shared/VMMain.cpp

@@ -37,6 +37,13 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 IPC::Channel VM::rootChannel;
 
+#ifdef BUILD_VM_NATIVE_EXE
+// When using native exe, turn this off if you want to use core dumps (*nix) or attach a debugger
+// upon crashing (Windows). Disabling it is like -nocrashhandler for Daemon.
+Cvar::Cvar<bool> VM::useNativeExeCrashHandler(
+	VM_STRING_PREFIX "nativeExeCrashHandler", "catch and log crashes/fatal exceptions in native exe VM", Cvar::NONE, true);
+#endif
+
 #ifdef BUILD_VM_IN_PROCESS
 // Special exception type used to cleanly exit a thread for in-process VMs
 // Using an anonymous namespace so the compiler knows that the exception is
@@ -159,9 +166,15 @@ NORETURN static void TerminateHandler()
 #ifdef __native_client__
 	// Using a lambda triggers -Wformat-security...
 #	define DispatchError(...) snprintf(realErrorMessage, sizeof(realErrorMessage), __VA_ARGS__)
-#else
+#elif defined(BUILD_VM_NATIVE_EXE)
 	auto DispatchError = [](const char* msg, const auto&... fmtArgs) {
-		Sys::Error(msg, fmtArgs...);
+		if (VM::useNativeExeCrashHandler.Get()) {
+			Sys::Error(msg, fmtArgs...);
+		} else {
+			Log::Warn(XSTRING(VM_NAME) " VM terminating:");
+			Log::Warn(msg, fmtArgs...);
+			// fall through to abort() for core dump etc.
+		}
 	};
 #endif
 
@@ -199,7 +212,9 @@ int main(int argc, char** argv)
 	std::set_terminate(TerminateHandler);
 	// Set up crash handling for this process. This will allow crashes to be
 	// sent back to the engine and reported to the user.
+#ifdef __native_client__
 	Sys::SetupCrashHandler();
+#endif
 
 	try {
 		CommonInit(rootSocket);

src/shared/VMMain.h

@@ -38,6 +38,10 @@ namespace VM {
 	// Root channel used to communicate with the engine
 	extern IPC::Channel rootChannel;
 
+#ifdef BUILD_VM_NATIVE_EXE
+	extern Cvar::Cvar<bool> useNativeExeCrashHandler;
+#endif
+
 	// Functions each specific gamelogic should implement
 	void VMInit();
 	void VMHandleSyscall(uint32_t id, Util::Reader reader);