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To: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: gcc@gcc.gnu.org
Subject: Re: skip_evaluation
References: <m37hzkrjjd.fsf@google.com> <4A2FD0FE.8090508@gmail.com>
From: Ian Lance Taylor <iant@google.com>
Date: Wed, 10 Jun 2009 15:46:00 -0000
In-Reply-To: <4A2FD0FE.8090508@gmail.com> (Paolo Bonzini's message of "Wed\, 10 Jun 2009 17\:27\:58 +0200")
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Paolo Bonzini <paolo.bonzini@gmail.com> writes:

>> Presumably the early return is OK within a sizeof expression; it is OK
>> within an expression like (0 ? x : y)?
>
> From reading the code, I'd say yes.  The bug that Jason fixed is
> related to stuff that cannot appear within a constant expression
> except within sizeof -- for example
>
>    struct B {};
>    struct D : public B {
>        static const int i = sizeof((B*)(D*)0);
>    };
>
>    struct Z {};
>    struct A : Z {};
>    Z* implicitToZ (Z*);
>    struct B : A {
>        static const int i = sizeof(implicitToZ((B*)0));
>    };
>
>    struct B {};
>    struct D;
>    D* p;
>    struct D: public B {
>        static const int i = sizeof ((B*)p);
>    };
>
> (see PR27177).  All of these would still be forbidden within (0?x:y).

OK, but should they perhaps give an error which would perhaps not be
given if skip_evaluation is true?

Ian