# V2549. MISRA. Pointer to FILE should not be dereferenced.

This diagnostic rule is based on software development guidelines developed by MISRA (Motor Industry Software Reliability Association).

This rule applies only to C. A pointer to the standard type FILE must not be dereferenced, whether explicitly or implicitly. Copying this object is pointless as the copy will not show the same behavior. Direct use of a FILE object is forbidden because it may be incompatible with the accepted file stream handling design.

Explicit dereferencing is in fact ordinary dereferencing with the use of specific operators:

- *p;
- p->_Placeholder;
- p[0];

Implicit dereferencing involves calling a function inside which the pointer is dereferenced, for example, 'memcpy' or 'memcmp'.

Example of non-compliant code:

    void foo()
    {
      FILE *f = fopen(....);
      FILE *d = fopen(....);
      ....
      if (memcmp(f, d, sizeof(FILE)) == 0) { .... } // <=
      memset(d, 0, sizeof(*d));                     // <=
      *d = *f;                                      // <=
      ....
    }

This diagnostic is classified as:

MISRA-C-2012-22.5 MISRA-C-2023-22.5