c - How to wrap printf() into a function or macro?

Question

This might sound like an interview question but is actually a practical problem.

I am working with an embedded platform, and have available only the equivalents of those functions:

• printf()
• snprintf()

Furthermore, the printf() implementation (and signature) is likely to change in the near future, so calls to it have to reside in a separate module in order to be easy to migrate later.

Given that, can I wrap logging calls in some function or macro? The goal is that my source code calls THAT_MACRO("Number of bunnies: %d", numBunnies); in a thousand places, but calls to the above functions are seen only in a single place.

Compiler: arm-gcc -std=c99

Edit: just to mention, but post 2000 best practices and probably a lot earlier, inline functions are far better than macros for numerous reasons.

Answer 1

There are 2 ways to do this:

1. Variadric macro

   #define my_printf(...) printf(__VA_ARGS__)
   

2. function that forwards va_args

   #include <stdarg.h>
   #include <stdio.h>
   
   void my_printf(const char *fmt, ...) {
       va_list args;
       va_start(args, fmt);
       vprintf(fmt, args);
       va_end(args);
   }
   

There are also vsnprintf, vfprintf and whatever you can think of in stdio.