Using the indirection pattern for preprocessor stringification and concatenation

The C++ preprocessor provides two operators for transforming identifiers to strings and concatenating identifiers together. The first one, operator #, is called the stringizing operator, while the second one, operator ##, is called the token-pasting, merging, or concatenating operator. Although their use is limited to some particular cases, it is important to understand how they work.

Getting ready

For this recipe, you need to know how to define macros using the preprocessing directive #define.

How to do it...

To create a string from an identifier using the preprocessing operator #, use the following pattern:

1. Define a helper macro taking one argument that expands to #, followed by the argument:

   #define MAKE_STR2(x) #x
   

2. Define the macro you want to use, taking one argument that expands to the helper macro:

   #define MAKE_STR(x) MAKE_STR2(x)
   

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