Concatenating proprocessor macro FUNCTION with a string

Question

This should be trivial but I cannot seem to figure out how to concatenate __FUNCTION__ with strings especially on GCC -- although it works on VC++ (I'm porting some code to Linux)

#include <iostream>
#include <string>

#define KLASS_NAME  "Global"

int main()
{
    std::string msg = KLASS_NAME "::" __FUNCTION__;
    std::cout << msg << std::endl;
}

Online VC++ version

GCC error message

Test.cpp:9:36: error: expected ‘,’ or ‘;’ before ‘__FUNCTION__’
  std::string msg = KLASS_NAME "::" __FUNCTION__;

Update

Thanks to Chris, apparently adjacent string literals are concatenated [reference]. So VC++ may be correct in this case, until you consider that __FUNCTION__ is non-standard.

It's worth noting that __FUNCTION__ isn't standard and that __func__ isn't a string literal. — Qaz
– Qaz, Commented Mar 30, 2017 at 11:16
@AliAkberFaiz, That's the concatenation operator and it's required to produce a valid token. — Qaz
– Qaz, Commented Mar 30, 2017 at 11:17
Why one earth does VC++ even accept KLASS_NAME "::" __FUNCTION__ if its not valid? I'm assuming its not. — Olumide
– Olumide, Commented Mar 30, 2017 at 11:33

Beginner · Accepted Answer · 2017-03-30 11:18:32Z

1

You need a concatenation operator and explicitly construct the string such that the right concatenation operator is found:

#include <iostream>
#include <string>

#define KLASS_NAME  "Global"

int main()
{
    std::string msg = std::string(KLASS_NAME) + "::" + __FUNCTION__;
    std::cout << msg << std::endl;
}

Live example: http://ideone.com/vn4yra

answered Mar 30, 2017 at 11:18

Beginner

5,5476 gold badges41 silver badges76 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Concatenating proprocessor macro FUNCTION with a string

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related