How to use Macro argument as string literal?

c++ c-preprocessor string-literals
Ian picture Ian · May 9, 2012 · Viewed 118.6k times · Source

I am trying to figure out how to write a macro that will pass both a string literal representation of a variable name along with the variable itself into a function.

For example given the following function.

void do_something(string name, int val)
{
   cout << name << ": " << val << endl;
}

I would want to write a macro so I can do this:

int my_val = 5;
CALL_DO_SOMETHING(my_val);

Which would print out: my_val: 5

I tried doing the following:

#define CALL_DO_SOMETHING(VAR) do_something("VAR", VAR);

However, as you might guess, the VAR inside the quotes doesn't get replaced, but is just passed as the string literal "VAR". So I would like to know if there is a way to have the macro argument get turned into a string literal itself.

Answer

Morwenn picture Morwenn · May 9, 2012

Use the preprocessor # operator:

#define CALL_DO_SOMETHING(VAR) do_something(#VAR, VAR);

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