On Mon, 24 May 2021, Uecker, Martin wrote:
> - else if (VOID_TYPE_P (TREE_TYPE (type1))
> - && !TYPE_ATOMIC (TREE_TYPE (type1)))
> - {
> - if ((TREE_CODE (TREE_TYPE (type2)) == ARRAY_TYPE)
> - && (TYPE_QUALS (strip_array_types (TREE_TYPE (type2)))
> - & ~TYPE_QUALS (TREE_TYPE (type1))))
> - warning_at (colon_loc, OPT_Wdiscarded_array_qualifiers,
> - "pointer to array loses qualifier "
> - "in conditional expression");
> -
> - if (TREE_CODE (TREE_TYPE (type2)) == FUNCTION_TYPE)
> + else if ((VOID_TYPE_P (TREE_TYPE (type1))
> + && !TYPE_ATOMIC (TREE_TYPE (type1)))
> + || (VOID_TYPE_P (TREE_TYPE (type2))
> + && !TYPE_ATOMIC (TREE_TYPE (type2))))
Here you're unifying the two cases where one argument is (not a null
pointer constant and) a pointer to qualified or unqualified void (and the
other argument is not a pointer to qualified or unqualified void). The
!TYPE_ATOMIC checks are because of the general rule that _Atomic is a type
qualifier only syntactically, so _Atomic void doesn't count as qualified
void for this purpose.
> + {
> + tree t1 = TREE_TYPE (type1);
> + tree t2 = TREE_TYPE (type2);
> + if (!VOID_TYPE_P (t1))
> + {
> + /* roles are swapped */
> + t1 = t2;
> + t2 = TREE_TYPE (type1);
> + }
But here you don't have a TYPE_ATOMIC check before swapping. So if t1 is
_Atomic void and t2 is void, the types don't get swapped.
> + /* for array, use qualifiers of element type */
> + if (flag_isoc2x)
> + t2 = t2_stripped;
> + result_type = build_pointer_type (qualify_type (t1, t2));
And then it looks to me like this will end up with _Atomic void * as the
result type, when a conditional expression between _Atomic void * and
void * should actually have type void *.
If that's indeed the case, I think the swapping needs to occur whenever t1
is not *non-atomic* void, so that the condition for swapping matches the
condition checked in the outer if. (And of course there should be a
testcase for that.)
I didn't see any other issues in this version of the patch.
--
Joseph S. Myers
jos...@codesourcery.com
