Error: invalid operands of types ‘const char [35]’ and ‘const char [2]’ to binary ‘operator+’

Question

At the top of my file I have

#define AGE \"42\"

Later in the file I use ID multiple times including some lines that look like

Answer 1

You cannot concatenate raw strings like this. operator+ only works with two std::string objects or with one std::string and one raw string (on either side of the operation).

std::string s("...");
s + s; // OK
s + "x"; // OK
"x" + s; // OK
"x" + "x" // error

The easiest solution is to turn your raw string into a std::string first:

"Do you feel " + std::string(AGE) + " years old?";

Of course, you should not use a macro in the first place. C++ is not C. Use const or, in C++11 with proper compiler support, constexpr.