MISRA.DEFINE.BADEXP.CPP

Inappropriate macro expansion in a C++ source

MISRA-C++ Rule 16-2-2 (required): C++ macros shall only be used for include guards, type qualifiers, or storage class specifiers.

Rationale

These are the only permitted uses of macros. C++ offers const variable and function templates, which provide a type-safe alternative to the preprocessor.

Note that the use of macros for type qualifiers and storage class specifiers will break Rule 16—2—1.

Example

// The following are compliant
#define STOR extern                   // storage class specifier
                                      // Breaks Rule 16—2—1

// The following are non-compliant
#define CLOCK (xtal/16)               // Constant expression
#define PLUS2(X) ((X) + 2)            // Macro expanding to expression
#define PI 3.14159F                   // use const object instead
#define int32_t long                  // use typedef instead
#define STARTIF if(                   // language redefinition
#define INIT(value) {(value), 0, 0}   // braced initializer
#define HEADER "filename.h"           // string literal