Aliasing pre-condition not processed correctly if is_fresh clause it not standalone #8492
Description
CBMC Version: 6.3.1
The following proves successfully:
void dummy0(int *r, int *a)
__CPROVER_requires(__CPROVER_is_fresh(r, sizeof(*r)))
__CPROVER_requires(r == a)
__CPROVER_assigns(*r)
__CPROVER_ensures(*a==42) {
*r = 42;
}
/*
goto-cc harness.c --function harness -o a.out
goto-instrument --dfcc harness --enforce-contract dummy0 a.out b.out
cbmc b.out
*/
void harness(void) {
int *r;
int *a;
dummy0(r, a);
}The following does not:
void dummy0(int *r, int *a)
__CPROVER_requires(r != NULL && __CPROVER_is_fresh(r, sizeof(*r)))
__CPROVER_requires(r == a)
__CPROVER_assigns(*r)
__CPROVER_ensures(*a==42) {
*r = 42;
}
/*
goto-cc harness.c --function harness -o a.out
goto-instrument --dfcc harness --enforce-contract dummy0 a.out b.out
cbmc b.out
*/
void harness(void) {
int *r;
int *a;
dummy0(r, a);
}Even if the r != NULL clause is redundant, this is surprising -- is there dedicated logic for detecting is_fresh clauses which only works when is_fresh is used at the top-level in a requires clause?