ISO/IEC TS 17961 [filecpy]

The issue occurs when a pointer to a FILE object is dereferenced.

The Standard states that the address of a FILE object used to control a stream can be significant. Copying that object might not give the same behavior. This rule ensures that you cannot perform such a copy.

Directly manipulating a FILE object might be incompatible with its use as a stream designator.

#include <stdio.h>

void func(void) {
    FILE *pf1;
    FILE *pf2;
    FILE f3;

    pf2 = pf1;        /* Compliant */
    f3 = *pf2;        /* Non-compliant */
    pf2->_flags=0;    /* Non-compliant */
 }

In this example, the rule is violated when the FILE* pointer pf2 is dereferenced.