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Re: GCC aliasing rules: more aggressive than C99?

From: Paolo Bonzini <bonzini at gnu dot org>
To: Richard Guenther <richard dot guenther at gmail dot com>
Cc: Joshua Haberman <jhaberman at gmail dot com>, gcc at gcc dot gnu dot org
Date: Mon, 04 Jan 2010 10:51:05 +0100
Subject: Re: GCC aliasing rules: more aggressive than C99?
References: <loom.20100103T063932-636@post.gmane.org> <84fc9c001001030253g4911a5ebi97aab621b7505449@mail.gmail.com> <loom.20100103T225120-945@post.gmane.org> <84fc9c001001031425o18a0eaf3r29b808b3089a3e15@mail.gmail.com>

On 01/03/2010 11:25 PM, Richard Guenther wrote:

>    char charray[sizeof(long)] = {...};
>    long l = *(long*)charray;  // ok


not correct;)   (the lvalue has to be of character type, yours is of
type 'long' - the type of the actual object does not matter)

What would be correct instead is

memcpy ((char *) &l, charray, sizeof(long));

Paolo

References:
- GCC aliasing rules: more aggressive than C99?
  - From: Joshua Haberman
- Re: GCC aliasing rules: more aggressive than C99?
  - From: Richard Guenther
- Re: GCC aliasing rules: more aggressive than C99?
  - From: Joshua Haberman
- Re: GCC aliasing rules: more aggressive than C99?
  - From: Richard Guenther

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