test: cover native VM call argument packing

src/qcommon/vm.c

@@ -2077,15 +2077,10 @@ intptr_t QDECL VM_Call( vm_t *vm, int nargs, int callnum, ... )
 	// if we have a dll loaded, call it directly
 	if ( vm->entryPoint )
 	{
-		/* Pass three arg slots: native vmMain only receives nargs from varargs; zero the rest
-		 * so e.g. UI_GETAPIVERSION (nargs=0) does not read stack garbage. */
 		int32_t args[MAX_VMMAIN_CALL_ARGS-1];
-		Com_Memset( args, 0, sizeof( args ) );
 		va_list ap;
 		va_start( ap, callnum );
-		for ( i = 0; i < nargs; i++ ) {
-			args[i] = va_arg( ap, int32_t );
-		}
+		VM_BuildNativeModuleCallArgs( nargs, args, (int)ARRAY_LEN( args ), ap );
 		va_end( ap );
 
 		// add more arguments if you're changed MAX_VMMAIN_CALL_ARGS:

src/qcommon/vm_native_module.c

@@ -1,5 +1,6 @@
 #include "vm_native_module.h"
 #include <stdio.h>
+#include <string.h>
 
 int VM_BuildNativeModuleCandidates( const char *moduleName, char out[][MAX_QPATH], int maxCandidates ) {
 	int count = 0;
@@ -24,3 +25,23 @@ int VM_BuildNativeModuleCandidates( const char *moduleName, char out[][MAX_QPATH
 
 	return count;
 }
+
+void VM_BuildNativeModuleCallArgs( int nargs, int32_t *out, int maxArgs, va_list ap ) {
+	int i;
+	int copyCount;
+
+	if ( !out || maxArgs <= 0 ) {
+		return;
+	}
+
+	memset( out, 0, (size_t)maxArgs * sizeof( out[0] ) );
+
+	copyCount = nargs;
+	if ( copyCount > maxArgs ) {
+		copyCount = maxArgs;
+	}
+
+	for ( i = 0; i < copyCount; i++ ) {
+		out[i] = va_arg( ap, int32_t );
+	}
+}

src/qcommon/vm_native_module.h

@@ -1,6 +1,9 @@
 #ifndef VM_NATIVE_MODULE_H
 #define VM_NATIVE_MODULE_H
 
+#include <stdarg.h>
+#include <stdint.h>
+
 #include "q_shared.h"
 
 /*
@@ -11,4 +14,11 @@
  */
 int VM_BuildNativeModuleCandidates( const char *moduleName, char out[][MAX_QPATH], int maxCandidates );
 
+/*
+ * Packs native vmMain argument slots from VM_Call varargs. Native vmMain takes
+ * exactly three integer argument slots after the command; missing slots must be
+ * zero so low-arity calls such as UI_GETAPIVERSION cannot observe stack junk.
+ */
+void VM_BuildNativeModuleCallArgs( int nargs, int32_t *out, int maxArgs, va_list ap );
+
 #endif

tests/README.md

@@ -1,5 +1,5 @@
 # Tests
 
-- **Unit** (`BUILD_UNIT_TESTS=ON`): `unit_macros`, `unit_qmath`, `unit_surfaceflags`, `unit_qhelpers`, `unit_crc`, `unit_pathutil`, `unit_msg`, `unit_info`, `unit_cm_bounds`, `unit_parse`, `unit_endian` (CRC, COM path, `Info_*`, `COM_Parse*`, and endian tests use the same minimal `stub_qcommon_min.c` + `q_shared.c` + `q_math.c` link as `unit_qhelpers`; `unit_msg` links `msg.c` + `huffman_static.c` with `stub_qcommon_min.c`, `stub_msg_cvar.c`, and `-DDEDICATED`; `unit_cm_bounds` links `cm_bounds.c` + `q_math.c` only) — run `ctest -R unit_` or `./unit_*` from the build directory.
+- **Unit** (`BUILD_UNIT_TESTS=ON`): `unit_macros`, `unit_qmath`, `unit_surfaceflags`, `unit_qhelpers`, `unit_crc`, `unit_pathutil`, `unit_msg`, `unit_info`, `unit_cm_bounds`, `unit_parse`, `unit_endian`, `unit_vm_native_module` (CRC, COM path, `Info_*`, `COM_Parse*`, endian, and native VM module tests use the same minimal `stub_qcommon_min.c` + `q_shared.c` + `q_math.c` link as `unit_qhelpers` where needed; `unit_msg` links `msg.c` + `huffman_static.c` with `stub_qcommon_min.c`, `stub_msg_cvar.c`, and `-DDEDICATED`; `unit_cm_bounds` links `cm_bounds.c` + `q_math.c` only; `unit_vm_native_module` links `vm_native_module.c` only) — run `ctest -R unit_` or `./unit_*` from the build directory.
 - **Script regression tests**: `test_botlib_bounded_strings` (botlib string invariants). Run with `ctest -R test_botlib_bounded_strings` from the build directory.
 - **Validation**: `smoke_test`, `renderer_regression_check`, `check_artifacts`, `test_run_vulkan_script`, `test_compile_engine_lto`, `test_demo_game_pk3`, `test_vk_vegetation_dispatch_order`, `test_vulkan_mesh_shader_opt_in`, `test_vulkan_runtime_regressions`, `test_botlib_chat_message_bounds`, `test_vulkan_renderer_guards`, `test_vulkan_regression_source_guards`, `test_gltf_opengl_regressions`, `test_botlib_bounded_strings` — see `scripts/`, `tests/scripts/`, and `docs/RENDERER_CONFIDENCE.md`.

tests/unit/test_vm_native_module.c

@@ -2,6 +2,8 @@
  * Unit test: VM native module candidate naming
  * Run: ctest -R unit_vm_native_module
  */
+#include <stdarg.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <string.h>
 
@@ -64,6 +66,60 @@ static int test_candidate_limit(void) {
 	return 0;
 }
 
+static void build_call_args(int nargs, int32_t out[3], ...) {
+	va_list ap;
+
+	va_start(ap, out);
+	VM_BuildNativeModuleCallArgs(nargs, out, 3, ap);
+	va_end(ap);
+}
+
+static int test_native_call_args_zero_fill(void) {
+	int32_t out[3] = { 0x11111111, 0x22222222, 0x33333333 };
+
+	build_call_args(0, out);
+	ASSERT(out[0] == 0, "zero-arg call should clear arg0");
+	ASSERT(out[1] == 0, "zero-arg call should clear arg1");
+	ASSERT(out[2] == 0, "zero-arg call should clear arg2");
+
+	build_call_args(1, out, 1234);
+	ASSERT(out[0] == 1234, "one-arg call should copy arg0");
+	ASSERT(out[1] == 0, "one-arg call should clear arg1");
+	ASSERT(out[2] == 0, "one-arg call should clear arg2");
+
+	return 0;
+}
+
+static int test_native_call_args_copy_all_slots(void) {
+	int32_t out[3] = { 0 };
+
+	build_call_args(3, out, -1, 0x12345678, 42);
+	ASSERT(out[0] == -1, "three-arg call should copy arg0");
+	ASSERT(out[1] == 0x12345678, "three-arg call should copy arg1");
+	ASSERT(out[2] == 42, "three-arg call should copy arg2");
+
+	return 0;
+}
+
+static void build_call_args_limited(int nargs, int32_t out[3], int maxArgs, ...) {
+	va_list ap;
+
+	va_start(ap, maxArgs);
+	VM_BuildNativeModuleCallArgs(nargs, out, maxArgs, ap);
+	va_end(ap);
+}
+
+static int test_native_call_args_respect_limit(void) {
+	int32_t out[3] = { 77, 88, 99 };
+
+	build_call_args_limited(3, out, 2, 10, 20, 30);
+	ASSERT(out[0] == 10, "limited native args should copy arg0");
+	ASSERT(out[1] == 20, "limited native args should copy arg1");
+	ASSERT(out[2] == 99, "limited native args should not write past maxArgs");
+
+	return 0;
+}
+
 int main(void) {
 	if (test_empty_inputs() != 0) {
 		return 1;
@@ -74,6 +130,15 @@ int main(void) {
 	if (test_candidate_limit() != 0) {
 		return 1;
 	}
+	if (test_native_call_args_zero_fill() != 0) {
+		return 1;
+	}
+	if (test_native_call_args_copy_all_slots() != 0) {
+		return 1;
+	}
+	if (test_native_call_args_respect_limit() != 0) {
+		return 1;
+	}
 
 	printf("PASS: unit_vm_native_module\n");
 	return 0;