On 04/06/2017 04:11 PM, Bernd Edlinger wrote:
I think it is not too complicated to done in the C++ FE.
The FE looks for array of std::byte and unsigned char,
and sets the attribute when the final type is constructed.
What I am trying to do is just extend the semantic of may_alias
a bit, and then have the C++ FE use it in the way it has to.
We also need this for some POSIX and Linux kernel interfaces. A
C++-only solution would not help with that.
Here is what I want to write in the doc:
@item typeless_storage
@cindex @code{typeless_storage} type attribute
A type declared with this attribute behaves like a character type
with respect to aliasing semantics.
This is attribute is similar to the @code{may_alias} attribute,
except that it is not restricted to pointers.
As Jakub pointed out, this is not what we need here. An object of type
char does *not* have untyped storage. Accessing it as a different type
is still undefined.
The documentation says that the memory region is considered to by
untyped, like a memory region returned by malloc (but obviously not with
the implication that the memory region is separated from everything else).
Thanks,
Florian
