#ifdef, Conditional compilation directives
Syntax:
#if
#else
#endif
#if
#elif
#endif
1)The compiler only compiles the lines that follow the #if directive when evaluates to non-zero.
2)Otherwise, the compiler skips the lines that follow until it encounters the matching #else or #endif.
3)If the expression evaluates to false and there is a matching #else, the lines between the #else and the #endif are compiled.
4)#if directives can be nested, but matching #else and #endif directives must be in the same file as the #if.
5)#elif is like #else except the else block is only compiled if the expression after #elif is non-zero.
#ifdefevaluates to 1 if the symbol specified by has been previously
defined with a #define directive.
Example
Syntax:
#if
#else
#endif
#if
#elif
#endif
1)The compiler only compiles the lines that follow the #if directive when
2)Otherwise, the compiler skips the lines that follow until it encounters the matching #else or #endif.
3)If the expression evaluates to false and there is a matching #else, the lines between the #else and the #endif are compiled.
4)#if directives can be nested, but matching #else and #endif directives must be in the same file as the #if.
5)#elif is like #else except the else block is only compiled if the expression after #elif is non-zero.
#ifdef
defined with a #define directive.
Example
#ifdef DEBUG printf("Total space %d\n", space); #endif |
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