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Thread: Question about #ifndef

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should every c header file include:

code:
#ifndef __header_h__ #define __header_h__  #endif
also, should put function prototypes , other header files in between also, instance:
code:
#ifndef __header_h__ #define __header_h__  #include <math.h>  int addition (int x, int y);  #endif
or should function prototypes go outside of #endif? confused, help.

it's - preprocessor facilities of c/c++ (and other languages) powerful tool that, if used well, make life lot easier.

1 reason i'd second example, declarations in #ifndef/#endndef block make sure 1 particular set of declarations once during compilation of particular file.


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