Stringification char '#' using c/c++ macro on arm-linux-androideabi-gcc

Question

I have a macro like this.

#define TO_STR(x) #x

I can use this macro to make string without the input string between char " . Like :

const char* test = TO_STR(hello,macro);
std::cout << test << std::endl;

I can got : hello,macro correctly .

My question is : how can I deal with char # in the input string . Like :

const char* shaderprogram = TO_STR(#version 300 es \n);

This will cause an error , any suggestion ?

Answer 1

The first is illformed, since the preprocessor will treat the , as separating two arguments, not as part of an argument.

You could try creating a second macro

#define TO_STR2(a,b) TO_STR(a) "," TO_STR(b)

If you then want to do the same with three arguments, you would need to define another macro

#define TO_STR3(a,b,c) TO_STR2(a,b) "," TO_STR(c)

which is possible for more arguments, but messy - after all, macros aren't really intended to be used for this sort of thing.

The solution to the second is easy

const char* shaderprogram = "#" TO_STR(version 300 es \n);

The real solution, however, is to get away from any obsession of having a macro that allows you to leave the " characters off string literals. Only use the stringizing operator in a macro when it is the ONLY solution to the problem, not as the first tool of choice when there are alternatives.

After all, this

const char* shaderprogram = "#" TO_STR(version 300 es \n);   // blech!

is inferior to

const char* shaderprogram = "#version 300 es \n"; 

by several measures - including readability, maintainability, etc etc