sol2/examples/source/script_error_handling.cpp

#define SOL_ALL_SAFETIES_ON 1
#include <sol/sol.hpp>

#include <iostream>

int main(int, char**) {
	std::cout << "=== script error handling ===" << std::endl;

	sol::state lua;

	std::string code = R"(
bad&$#*$syntax
bad.code = 2
return 24
)";

	/* OPTION 1 */
	// Handling code like this can be robust
	// If you disable exceptions, then obviously you would
	// remove the try-catch branches, and then rely on the
	// `lua_atpanic` function being called and trapping errors
	// there before exiting the application
	{
		// script_default_on_error throws / panics when the
		// code is bad: trap the error
		try {
			int value = lua.script(
			     code, sol::script_default_on_error);
			// This will never be reached
			std::cout << value << std::endl;
			sol_c_assert(value == 24);
		}
		catch (const sol::error& err) {
			std::cout << "Something went horribly wrong: "
			             "thrown error"
			          << "\n\t" << err.what() << std::endl;
		}
	}

	/* OPTION 2 */
	// Use the script_pass_on_error handler
	// this simply passes through the protected_function_result,
	// rather than throwing it or calling panic
	// This will check code validity and also whether or not it
	// runs well
	{
		sol::protected_function_result result
		     = lua.script(code, sol::script_pass_on_error);
		sol_c_assert(!result.valid());
		if (!result.valid()) {
			sol::error err = result;
			sol::call_status status = result.status();
			std::cout << "Something went horribly wrong: "
			          << sol::to_string(status) << " error"
			          << "\n\t" << err.what() << std::endl;
		}
	}

	/* OPTION 3 */
	// This is a lower-level, more explicit way to load code
	// This explicitly loads the code, giving you access to any
	// errors plus the load status then, it turns the loaded
	// code into a sol::protected_function which is then called
	// so that the code can run you can then check that too, for
	// any errors The two previous approaches are recommended
	{
		sol::load_result loaded_chunk = lua.load(code);
		sol_c_assert(!loaded_chunk.valid());
		if (!loaded_chunk.valid()) {
			sol::error err = loaded_chunk;
			sol::load_status status = loaded_chunk.status();
			std::cout << "Something went horribly wrong "
			             "loading the code: "
			          << sol::to_string(status) << " error"
			          << "\n\t" << err.what() << std::endl;
		}
		else {
			// Because the syntax is bad, this will never be
			// reached
			sol_c_assert(false);
			// If there is a runtime error (lua GC memory
			// error, nil access, etc.) it will be caught here
			sol::protected_function script_func
			     = loaded_chunk
			            .get<sol::protected_function>();
			sol::protected_function_result result
			     = script_func();
			if (!result.valid()) {
				sol::error err = result;
				sol::call_status status = result.status();
				std::cout
				     << "Something went horribly wrong "
				        "running the code: "
				     << sol::to_string(status) << " error"
				     << "\n\t" << err.what() << std::endl;
			}
		}
	}

	std::cout << std::endl;

	return 0;
}