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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")

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Stringification

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

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Token concat

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

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Macro

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

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Error

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

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[Reference] If

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

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Defines

#define FOO
#define FOO "hello"

#undef FOO

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Includes

#include "file"

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Compiling

$ cpp -P file > outfile

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Reference

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