On Sun, Jan 13, 2019 at 06:54:05AM -0800, H.J. Lu wrote:
> > What always matters is whether we take address of a packed structure
> > field/non-static data member or whether we just read that field.
> > The former should be warned about, the latter not.
> >
>
> How about this patch? It checks if address is taken with NOP.
I'd like to first understand the convert_p argument to
warn_for_address_or_pointer_of_packed_member.
To me it seems you want to emit two different warnings, perhaps one
surpressed if the other one is emitted, but you actually from the start
decide which of the two you are going to check for. That is just weird.
Consider -O2 -Waddress-of-packed-member -Wno-incompatible-pointer-types:
struct __attribute__((packed)) S { char p; int a, b, c; };
int *
foo (int x, struct S *p)
{
return x ? &p->a : &p->b;
}
int *
bar (int x, struct S *p)
{
return (int *) (x ? &p->a : &p->b);
}
short *
baz (int x, struct S *p)
{
return x ? &p->a : &p->b;
}
short *
qux (int x, struct S *p)
{
return (short *) (x ? &p->a : &p->b);
}
This warns in foo, bar and qux, but doesn't warn in baz, because we've
decided upfront that that case is convert_p = true.
I would have expected that the convert_p argument isn't passed at all,
the function always does the diagnostics about taking address that is
done with !convert_p right now, and either do the pointer -> pointer
conversion warning somewhere else (wherever we detect a pointer to pointer
conversion, even in the middle of expression?), or do it wherever you do
currently, but again always if the orig_rhs and type pointer types are
different.
Jakub
