Macro concatenate created by VehpuS - https://repl.it/@VehpuS/Macro-concatenate

macro-val-concatenate-example.c

#include <stdio.h>
// https://gcc.gnu.org/onlinedocs/cpp/Concatenation.html

#define test(a) b ## a

int main(void) {
  char* bc = "Hello World\n";
  printf(test(c));
  return 0;
}