C++ concatenation in macro

Question

I have the following set of macros (which I got from the first answer for How can I use the compile time constant __LINE__ in a string?) defined in an attempt to have a macro 'LOCATION_PREFIX' that I can use to "capture" the location of a line of code (will be passed to other functions that will perform logging).

#define STRINGIZE(f,l) STRINGIZE2(f) "(" STRINGIZE2(l)"):"
#define STRINGIZE2(x) #x
#define LOCATION_PREFIX STRINGIZE(__FILE__, __LINE__)

int main(){

printf("%s here\n", LOCATION_PREFIX);
printf("%s over here\n", LOCATION_PREFIX);

return 1;
}

Output:

"t.cpp"(8): here
"t.cpp"(9): over here

I want the output to be:

t.cpp(8): here
t.cpp(9): over here

Any help is greatly appreciated !

Michael Wild · Accepted Answer · 2013-03-20 15:30:22Z

4

You don't need the first STRINGIZE2 invocation, as the file name is already a quoted string:

#define STRINGIZE(f,l) f "(" STRINGIZE2(l) "):"
#define STRINGIZE2(x) #x
#define LOCATION_PREFIX STRINGIZE(__FILE__, __LINE__)

int main(){
  printf("%s here\n", LOCATION_PREFIX);
  printf("%s over here\n", LOCATION_PREFIX);

  return 1;
}

answered Mar 20, 2013 at 15:30

Michael Wild

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3 Comments

Scottymac Over a year ago

Cheers ! Works perfectly, thank you very much for the quick response... will accept the answer as soon as I can.

Michael Wild Over a year ago

Notice, that you then can also drop the f argument of STRINGIZE and directly put __FILE__ in there. I didn't do it so there's a clear relation to your code, though.

Scottymac Over a year ago

made the change to remove the passing of FILE, STRINGIZE now only takes (l).

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