Something between __func__ and __PRETTY_FUNCTION__

问题:

I work with g++ 4.8.1 and use these two macros for debugging. However, the __func__ macro gives me only the function name, which might be misleading in the case you have many functions with the same name in different classes. The __PRETTY_FUNCTION__ macro produces the whole function signature - with return type, class name and all arguments, which can be very long.

I'd like to have something between - a macro, which will give me only class name and function name. Any way to achieve that?

回答1:

Inspired by this, I created the following macro __COMPACT_PRETTY_FUNCTION__:

std::string computeMethodName(const std::string& function, const std::string& prettyFunction);

#define __COMPACT_PRETTY_FUNCTION__ computeMethodName(__FUNCTION__,__PRETTY_FUNCTION__).c_str() //c_str() is optional


std::string computeMethodName(const std::string& function, const std::string& prettyFunction) {
    size_t locFunName = prettyFunction.find(function); //If the input is a constructor, it gets the beginning of the class name, not of the method. That's why later on we have to search for the first parenthesys
    size_t begin = prettyFunction.rfind(" ",locFunName) + 1;
    size_t end = prettyFunction.find("(",locFunName + function.length()); //Adding function.length() make this faster and also allows to handle operator parenthesys!
    if (prettyFunction[end + 1] == ')')
        return (prettyFunction.substr(begin,end - begin) + "()");
    else
        return (prettyFunction.substr(begin,end - begin) + "(...)");
}

What it does:

• It takes __PRETTY_FUNCTION__
• It removes return type and all arguments
• If the function has zero arguments, it appends (), otherwise (...)

Features:

• Handles namespaces, constructors and so on
• Works also with the parenthesis operator!

Limitations:

• It only works with gcc
• Created at runtime rather than compile time
• Heap allocated.
• Does not work for lambdas, __FUNCTION__ and __PRETTY_FUNCTION__ don't match... I would almost call it a compiler bug :)
  • __FUNCTION__ sees an operator()
  • __PRETTY_FUNCTION__ sees <lambda(...)>

回答2:

Unfortunatly, I don't think this can be done easily. I am one of those that don't understand why nobody ever proposed the implementation of a __CLASS__ macro, that could expand to the current class, similarly to all the macros defined by GCC, for example.

I agree that these macros are great help in some difficult debugging situations. Probably difficult to implement.