C Preprocessor cheatsheet

The C preprocessor is the macro preprocessor for the C, Objective-C, and C++ computer programming languages. The preprocessor provides the ability for the inclusion of header files, macro expansions, conditional compilation, and line control. C Preprocessor Cheat Sheet is quick reference for the C macro preprocessor, which can be used independently of C/C++.

File and line

#define LOG(msg) console.log(__FILE__, __LINE__, msg)
#=> console.log("file.txt", 3, "hey")

Stringification

#define STR(name) #name
char * a = STR(object);   #=> char * a = "object";

Token concat

#define DST(name) name##_s name##_t
DST(object);   #=> object_s object_t;

Macro

#define DEG(x) ((x) * 57.29)

Error

#if VERSION == 2.0
  #error Unsupported
  #warning Not really supported
#endif

[Reference] If

#ifdef DEBUG
  console.log('hi');
#elif defined VERBOSE
  ...
#else
  ...
#endif

Defines

#define FOO
#define FOO "hello"

#undef FOO

Includes

#include "file"

Compiling

$ cpp -P file > outfile

Reference

• https://en.wikipedia.org/wiki/C\_preprocessor
• https://cheatsheetmaker.com