On Mon, 3 May 2021, Liu Hao wrote:
在 2021-05-03 20:52, Martin Storsjö 写道:
On Mon, 3 May 2021, Christian Franke wrote:
Would plain '... = 0' without cast also work ? IIRC it should since C89
:-)
That doesn't work either - clang seems to consider the cast (either
implicit or explicit) between a integer or pointer-to-integer and a
pointer-to-function as something which isn't a compile time constant, in
this context...
`0` itself is required to be a null pointer constant (not just `0`, but also
any integer constant expression that equals zero, such as `1+1-2`). There is
no cast in-between. [1]
[1] https://gcc.godbolt.org/z/Kv3edeW1j
Sure. However in practice, with e.g. code like this:
typedef void (*fp)(void);
_Atomic fp ptr1 = ((void(*)(void))0);
_Atomic fp ptr2 = ((void*)0);
Clang accepts ptr1 but errors out on ptr2:
https://gcc.godbolt.org/z/3YW6EsGP4
In practice it shouldn't really matter, because as Jacek points out, we
should be able to do without the atomics just fine in practice here.
// Martin
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