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Re: [PATCH] Add a new type attribute always_alias (PR79671)

On 04/06/2017 09:16 PM, Richard Biener wrote:

On April 6, 2017 8:12:29 PM GMT+02:00, Bernd Edlinger <bernd.edlinger@hotmail.de> wrote:

But isn't the effective type changed by the assignment b[1] = 0;
as described in 6.5(6):
"If a value is stored into an object having no declared type through an
lvalue having a type that is not a character type, then the type of the
lvalue becomes the effective type of the object for that access and for
subsequent accesses that do not modify the stored value."


Yes.  I think the example is valid.  At least GCCs memory model makes it so.
As far as I understand the standard, C does not permit changing the effective type of an object if it has a declared type (at least not without a union). If GCC supports it, that's an undocumented GCC extension. 

Thanks,
Florian
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