fix: catch C++ exceptions in API bind wrapper

If a C++ exception escapes a bound function, this code now catches it
and yields the exception text as an error message via Lua machinery.

Optimally the wrapped code should handle exceptions intelligently, but
if it doesn't, this is the ultimate safety measure.

Author: zao

engine/core/core_image.cpp

@@ -98,7 +98,7 @@ image_c* image_c::LoaderForFile(IConsole* conHnd, const char* fileName)
 	}
 
 	// Detect first by extension, as decompressing could be expensive.
-	auto p = std::filesystem::u8path(fileName);
+	auto p = std::filesystem::path(fileName); // NOTE(LV): This should be u8path later.
 	if (p.extension() == ".zst") {
 		auto inner = p.filename();
 		inner.replace_extension();
@@ -452,7 +452,7 @@ bool gif_c::Save(const char* fileName)
 
 bool dds_c::Load(const char* fileName, std::optional<size_callback_t> sizeCallback)
 {
-	auto p = std::filesystem::u8path(fileName);
+	auto p = std::filesystem::path(fileName); // NOTE(LV): This should be u8path later.
 	// Open file
 	fileInputStream_c in;
 	if (in.FileOpen(fileName, true))

ui_api.cpp

@@ -154,11 +154,15 @@ static int l_##Name(lua_State* L) {                                \
 	int (*fun)(lua_State*) = [](lua_State* L) SG_NOINLINE -> int { \
 		try
 
-#define SG_LUA_CPP_FUN_END()                          \
-		catch (ui_expectationFailed_s) { return -1; } \
-    };                                                \
-	int rc = fun(L);                                  \
-	if (rc < 0) { LuaErrorWrapper(L); }               \
+#define SG_LUA_CPP_FUN_END()                                    \
+		catch (ui_expectationFailed_s) { return -1; }           \
+		catch (std::exception& e) {                             \
+			lua_pushfstring(L, "C++ exception:\n%s", e.what()); \
+			return -1;                                          \
+		}                                                       \
+    };                                                          \
+	int rc = fun(L);                                            \
+	if (rc < 0) { LuaErrorWrapper(L); }                         \
 	return rc; }
 
 // ===============
@@ -386,14 +390,14 @@ static int l_imgHandleGC(lua_State* L)
 	return 0;
 }
 
-static int l_imgHandleLoad(lua_State* L)
+SG_LUA_CPP_FUN_BEGIN(imgHandleLoad)
 {
 	ui_main_c* ui = GetUIPtr(L);
-	ui->LAssert(L, ui->renderer != NULL, "Renderer is not initialised");
+	ui->LExpect(L, ui->renderer != NULL, "Renderer is not initialised");
 	imgHandle_s* imgHandle = GetImgHandle(L, ui, "Load", false);
 	int n = lua_gettop(L);
-	ui->LAssert(L, n >= 1, "Usage: imgHandle:Load(fileName[, flag1[, flag2...]])");
-	ui->LAssert(L, lua_isstring(L, 1), "imgHandle:Load() argument 1: expected string, got %s", luaL_typename(L, 1));
+	ui->LExpect(L, n >= 1, "Usage: imgHandle:Load(fileName[, flag1[, flag2...]])");
+	ui->LExpect(L, lua_isstring(L, 1), "imgHandle:Load() argument 1: expected string, got %s", luaL_typename(L, 1));
 	const char* fileName = lua_tostring(L, 1);
 	char fullFileName[512];
 	if (strchr(fileName, ':') || !ui->scriptWorkDir) {
@@ -422,12 +426,13 @@ static int l_imgHandleLoad(lua_State* L)
 			flags |= TF_NEAREST;
 		}
 		else {
-			ui->LAssert(L, 0, "imgHandle:Load(): unrecognised flag '%s'", flag);
+			ui->LExpect(L, 0, "imgHandle:Load(): unrecognised flag '%s'", flag);
 		}
 	}
 	imgHandle->hnd = ui->renderer->RegisterShader(fullFileName, flags);
 	return 0;
 }
+SG_LUA_CPP_FUN_END()
 
 static int l_imgHandleUnload(lua_State* L)
 {