On Wed, 24 Aug 2022, Marek Polacek via Gcc-patches wrote:
> Ah, okay. I had just copied what we do in C++ in null_ptr_cst_p and the
> rest of the patch worked under that assumption. I've added some tests
> for this too. Except I don't really understand the _Generic comment so
> I only have tests for _Generic that were in the previous version.
The point is that e.g.
_Generic(0, int : nullptr)
is treated the same as nullptr (so is a null pointer constant), just as
(nullptr) is.
> Thanks, tests added to c2x-nullptr-1.c:test1. I notice that 6.3.2.4 still
> says "The type nullptr_t may be converted to bool or to a pointer type";
> isn't it missing the ", void" here too?
In general none of the subclauses under 6.3.2 about individual kinds of
types tend to discuss the possibility of conversion to void.
> +/* Simple assignment. */
> +void
> +test4 (void)
> +{
> + /* -- the left operand has an atomic, qualified, or unqualified version of
> + the nullptr_t type and the type of the right is nullptr_t; */
> + nullptr_t n1;
> + n1 = nullptr;
> + const nullptr_t n2 = nullptr;
> + _Atomic nullptr_t n3 = nullptr;
> + volatile nullptr_t n4 = nullptr;
These qualified cases are all actually initialization, not assignment; I
think both assignment and initialization (and argument passing and return)
should be tested for the permitted cases for assignment.
> +/* Test nullptr_t from <stddef.h.. */
Typo, "<stddef.h." should be <stddef.h>".
> +/* If a second or third operand of type nullptr_t is used that is not a null
> + pointer constant and the other operand is not a pointer or does not have
> + itself nullptr_t, a constraint is violated even if that other operand is
> + a null pointer constant such as 0. */
The "that is not a null pointer constant" in that footnote is a bit odd,
since it's also a constraint violation (and should be tested as such) to
have a conditional expression between e.g. nullptr and 0.
--
Joseph S. Myers
[email protected]
