String concatenation using preprocessor

Question

is it possible to concatenate strings during preprocessing?

I found this example

#define H "Hello "
#define W "World!"
#define HW H W

printf(HW); // Prints "Hello World!"

However it does not work for me - prints out "Hello" when I use gcc -std=c99

UPD This example looks like working now. However, is it a normal feature of c preprocessor?

Answer 1

Concatenation of adjacent string litterals isn't a feature of the preprocessor, it is a feature of the core languages (both C and C++). You could write:

printf("Hello "
       " world\n");