Confusion can arise when blocks of code are included or excluded by the use of conditional compilation directives which are spread over multiple files. Requiring that a #if directive be terminated within the same file reduces the visual complexity of the code and the chance that errors will be made during maintenance.

Note: #if directives may be used within included files provided they are terminated within the same file.

Example

/* file1.c */ 
#ifdef A             /* Compliant    */ 
#include "file1.h" 
#endif 
/* End of file1.c  */

/* file2.c */ 
#if 1                /* Non-compliant */ 
#include "file2.h" 
/* End of file2.c*/

/* file1.h */ 
#if 1                /* Compliant    */ 
#endif 
/* End of file1.h */

/* file2.h */ 
#endif 
/* End of file1.h */

MISRA-C 2004 Rule 19.17 (required): All `#else, #elif` and `#endif` preprocessor directives shall reside in the same file as the `#if` or `#ifdef` directive to which they are related.

#elif in an improper file.

This rule is also covered by MISRA.ELSE.OTHERFILE and MISRA.ENDIF.OTHERFILE.

When the inclusion and exclusion of blocks of statements is controlled by a series of preprocessor directives, confusion can arise if all of the relevant directives do not occur within one file. This rule requires that all preprocessor directives in a sequence of the form #if / #ifdef ... #elif ... #else ... #endif shall reside in the same file. Observance of this rule preserves good code structure and avoids maintenance problems.

Notice that this does not preclude the possibility that such directives may exist within included files so long as all directives that relate to the same sequence are located in one file.

Example

file.c

#define A
...
#ifdef A
...
#include "file1.h"
#
#endif
...
#if 1
#include "file2.h"
...
EOF

file1.h

#if 1
...
#endif /* Compliant */
EOF

file2.h

...
#endif /* Not compliant */

MISRA-C++ 2008 Rule 16-1-2 (required): All #else, #elif and #endif preprocessor directives shall reside in the same file as the #if or #ifdef directive to which they are related.

This rule is also covered by MISRA.ELSE.OTHERFILE and MISRA.ENDIF.OTHERFILE.

Rationale

When the inclusion and exclusion of blocks of statements is controlled by a series of preprocessor directives, confusion can arise if all of the relevant directives do not occur within one file. This rule requires that all preprocessor directives in a sequence of the form #if / #ifdef ... #elif ... #else ... #endif shall reside in the same file. Observance of this rule preserves good code structure and avoids maintenance problems.

Notice that this does not preclude the possibility that such directives may exist within included files provided that all directives that relate to the same sequence are located in one file.

Example

// file.cpp
#define A
...
#ifdef A
...
#include "file1.hpp"
#
#endif
...
#if 1
#include "file2.hpp"
...
// file1.hpp
#if 1
...
#endif  // Compliant
// file2.hpp
...
#endif  // Non-compliant

MISRA.ELIF.OTHERFILE

MISRA C 2012 Rule 20.14: All #else, #elif and #endif preprocessor directives shall reside in the same file as the #if, #ifdef or #ifndef directive to which they are related

Rationale

Example

MISRA-C 2004 Rule 19.17 (required): All #else, #elif and #endif preprocessor directives shall reside in the same file as the #if or #ifdef directive to which they are related.

Example

MISRA-C++ 2008 Rule 16-1-2 (required): All #else, #elif and #endif preprocessor directives shall reside in the same file as the #if or #ifdef directive to which they are related.

Rationale

Example

MISRA-C 2004 Rule 19.17 (required): All `#else, #elif` and `#endif` preprocessor directives shall reside in the same file as the `#if` or `#ifdef` directive to which they are related.