I have a C program which I am NOT allowed to edit that looks like this:
#include <stdio.h>
#ifndef YEAR
#define YEAR "2013"
#endif
int main(){
printf("Hello world from " YEAR "\n");
return 0;
}
I need to create a makefile to compile this program and change the YEAR to 2014, so that the output will be "Hello world from 2014" without editing the C program. How can I do this?
The compilation command should start with gcc -Wall -DYEAR='"2014"'. It is up to you to code your Makefile with a suitable CFLAGS settings. This answer should be inspirational.
Just pass a preprocessor directive with the -D parameter, for example:
$ cat tmp.c
#include <stdio.h>
#ifndef YEAR
#define YEAR "2013"
#endif
int main(){
printf("Hello world from " YEAR "\n");
return 0;
}
$ gcc -DYEAR=\"1234\" tmp.c -o tmp && ./tmp
Hello world from 1234
tmp.c as a source file (not tmp.cpp) and gcc as a compiler (not g++).
-Doption.