Difference between preprocessor directives #if and #ifdef -

January 15, 2011

The difference between the two following preprocessor control statements (if any).

#if

and

  #ifdef

You can display the difference by:

  #define FOO 0 #if FOO // This is not compiled This will be #endif #ifdefFoo // will be compiled for the  value  symbol #endif

#if while #ifdef checks the symbol existence (regardless of its value).

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Difference between preprocessor directives #if and #ifdef -

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