Synopsis

Ensure that integer conversions do not result in lost or misinterpreted data.

Enabled by default

Yes

Severity/Certainty

High/Medium

Full description

Integer conversions, both implicit and explicit (using a cast), must be guaranteed not to result in lost or misinterpreted data. This is particularly true for integer values that originate from untrusted sources and are used in pointer arithmetic, variable length array declaration, array subscription, and library function arguments that are of unsigned char types or represent sizes. This check is identical to ATH-overflow-cast.

Coding standards

Code examples

The following code example fails the check and will give a warning:

#include <limits.h>

void example(void) {
    unsigned long int u_a = ULONG_MAX;
    signed char sc;
    sc = (signed char)u_a; /* Cast eliminates warning */
    /* ... */
}

The following code example passes the check and will not give a warning about this issue:

#include <limits.h>

void example(void) {
    unsigned long int u_a = ULONG_MAX;
    signed char sc;
    if (u_a <= SCHAR_MAX) {
        sc = (signed char)u_a;  /* Cast eliminates warning */
    } else {
        /* Handle error */
    }
}