Predicate to describe overlapping pointers

[feliperodri]

CBMC version: 5.67.0
Operating system: N/A

We need to describe pointers that may overlap, for example an array and a pointer within that array. Currently, we have prototype same_space to express this as follows:

bool same_space(const void *a, const void *b) {
    size_t a_size = __CPROVER_OBJECT_SIZE(a);
    size_t a_offset = __CPROVER_POINTER_OFFSET(a);
    void *a_base = a - a_offset;
    size_t temp = nondet_size_t();
    size_t b_delta = MIN(temp, a_size - ((size_t) 1));
    return (b == a_base + b_delta);
}

The issue is that any proof that uses this primitive must disable the pointer-primitive-check CBMC flag, which is something that should be used in memory safety proofs. We need to disable the flag in order to use the __CPROVER_OBJECT_SIZE and __CPROVER_POINTER_OFFSET functions. We should be able to resolve this temporarily by just disabling the flag in a pragma, but this is not supported. There is a GitHub issue addressing this here.

[remi-delmas-3000]

PR #7401 adds support for

bool __CPROVER_pointer_in_range_dfcc(void *lb, void *ptr, void *ub);

which holds iff lb and ub are valid pointers to the same object and lb <= ptr && ptr <= ub.

We could close the issue once the PR is merged