如何制作一个 C++ 宏来检查条件，如果不满足则打印错误并执行用户块？

Question

I want to make an assertion-like macro that can be used like so

CHECKED_LOG(window != nullptr, "Window must be initialized")
{
    DoSomethingCleanupFunction();
    return false;
}

which should expand to something like

if (!(EXPR))
{
    LOG_MESSAGE("Error: window != nullptr : " + MSG);
    { /* user block */ }
}

Is there a way to do this without overcomplicating source code with some kind of classes, that use RAII to call all that logic and without double call of !(EXPR) ? I also want that to look natural, not

CHECKEDLOG(...)
  Logic();
} // <---- closing brace with opening one

Maybe some preprocessor placeholders for block after the macro of braces magic?

In the end i want something like that:

bool Initialize()
{
   window = InitWindow();
   CHECKED_LOG(window != nullptr, "Couldn't initialize window")
   {
       Stop();
       return false;
   }

   inputHandler = InitInputHandler();
   CHECKED_LOG(inputHandler != nullptr, "Couldn't initialize input handler")
   {
       Stop();
       return false;
   }
}

and the expansion

bool Initialize()
{
   window = InitWindow();
   if (! (window != nullptr))
   {
       LOG_ERROR("window != nullptr", "Couldn't initialize window");
       Stop();
       return false;
   }

   inputHandler = InitInputHandler();
   if (! (inputHandler != nullptr))
   {
       LOG_ERROR("inputHandler != nullptr", "Couldn't initialize input handler");
       Stop();
       return false;
   }
}

Answer 1

Is there a way to do this without overcomplicating source code with some kind of classes, that use RAII to call all that logic and without double call of?(EXPR)?

Put LOG_MESSAGE inside if with a comma operator that evaluates to true.

#define CHECKED_LOG(EXPR, MSG) \
    if (!(EXPR) && (LOG_MESSAGE("Error: " #EXPR " : " + MSG), 1))

I would name this macro just IF_NOT_THEN_LOG or similar, first so that developer knows it's an if , then - CHECKED is an adjective, there is no object here, EXPR is something to do so you if on that expression.

Overall, there is a fear associated with such macros. They hide a flow control statement, they usually lead to more complicated code and end up in a spaghetti code. Lambda, RAII and exception handling were invented into the language because it's simpler, clearer and more safe to work with them.