Mikroelektronika MIKROE-738 Datenbogen

262

mikoC PRO for PIC32

MikroElektronika

Conditional compilation directives are typically used to make source programs easy to change and easy to compile 

in  different  execution  environments. The  mikroC  PRO  for  PIC32  supports  conditional  compilation  by  replacing  the 

appropriate source-code lines with a blank line.

All conditional compilation directives must be completed in the source or include file in which they have begun.

Directives #if, #elif, #else, and #endif

The conditional directives 

#if

,

 #elif

,

 #else

, and

 #endif

 work very similar to the common C conditional statements. 

If the expression you write after 

#if

 has a nonzero value, the line group immediately following the 

#if

 directive is 

retained in the translation unit.

The syntax is:

#if constant_expression_1

[#elif constant_expression_2

  ...

[#elif constant_expression_n

[#else

#endif

Each 

#if

 directive in a source file must be matched by a closing 

#endif

 directive. Any number of

 #elif

 directives 

can appear between 

#if 

and 

#endif

 directives, but at most one 

#else

 directive is allowed. The 

#else

 directive, if 

present, must be the last directive before 

#endif

.

 can be any program text that has meaning to compiler or preprocessor. The preprocessor selects a single 

section

 by evaluating 

constant_expression

 following each 

#if 

or

 #elif

 directive until it finds a true (nonzero) 

constant expression. The constant expressions are subject to macro expansion.

If all occurrences of constant-expression are false, or if no

 #elif

 directives appear, the preprocessor selects the text 

block after the 

#else

 clause. If the 

#else

 clause is omitted and all instances of 

 in the 

#if 

block are false, no 

 is selected for further processing.

Any processed section can contain further conditional clauses, nested to any depth. Each nested 

#else

,

 #elif

, or

 

#endif 

directive belongs to the closest preceding the

 #if

 directive.

The net result of the preceding scenario is that only one code 

 (possibly empty) will be compiled.