MISRA.UNDEF

Undef usage.

MISRA C 2012 Rule 20.5: #undef should not be use

Category: Advisory

Analysis: Decidable, Single Translation Unit

Applies to: C90, C99

Rationale

The use of #undef can make it unclear which macros exist at a particular point within a translation unit.

Example

#define QUALIFIER volatile

#undef QUALIFIER               /* Non-compliant */

void f ( QUALIFIER int32_t p ) 
{
  while ( p != 0 ) 
  {
    ;                          /* Wait... */ 
  } 
}

MISRA-C 2004 Rule 19.6 (required): #undef shall not be used.

Undef usage.

#undef should not normally be needed. Its use can lead to confusion with respect to the existence or meaning of a macro when it is used in the code.

MISRA-C++ 2008 Rule 16-0-3 (required): #undef shall not be used.

Rationale

#undef should not normally be needed. Its use can lead to confusion with respect to the existence or meaning of a macro when it is used in the code.

Example

#ifndef MY_HDR
#define MY_HDR
  
#undef MY_HDR    // Non-compliant

#endif