On 2023-08-01 17:35, Qing Zhao wrote:
typedef struct
{
int a;
} A;
size_t f()
{
A *p = malloc (1);
return __builtin_object_size (p, 0);
Correction, that should be __builtin_object_size (p->a, 0).
Actually, it should be __builtin_object_size(p->a, 1).
For __builtin_object_size(p->a,0), gcc always uses the allocation size for the
whole object.
Right, sorry, I mistyped, twice in fact; it should have been
__bos(&p->a, 1) :)
GCC’s current behavior is:
For the size of the whole object, GCC currently always uses the allocation size.
And for the size in the sub-object, GCC chose the smaller one among the
allocation size and the TYPE_SIZE.
Is this correct behavior?
Yes, it's deliberate; it specifically checks on var != pt_var, which can
only be true for subobjects.
Thanks,
Sid
