Format
#if Val...#elif Val2...#else...#endif
Args
Val: A logical expression.
The #if statement is used to conditionally compile code. If Val is true (non-zero), the code following the #if statement will be compiled. Otherwise, compilation skips to the next #elif, #else, or #endif statement.
The function defined() can be used in the conditional expression. It is true if its argument is a defined macro (with #define) and false otherwise.
#if defined(DEBUG)
// This code will be compiled if DEBUG is
// defined
#else
// This code will be compiled if DEBUG is
// not defined
#endifYou can also use fexists() in a conditional to check if a file exists.