gcl-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Gcl-devel] Re: [Axiom-developer] GCC/GCL warning messages


From: Camm Maguire
Subject: [Gcl-devel] Re: [Axiom-developer] GCC/GCL warning messages
Date: 02 Mar 2007 17:04:59 -0500
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2

Greetings!

Gabriel Dos Reis <address@hidden> writes:

> address@hidden writes:
> 
> | Camm,
> | 
> | I'm building the next Axiom release. During the GCL build I see a large
> | number of messages that read:
> | 
> | gcl_defmacro.c:In function `L12':
> | gcl_defmacro.c:79: warning: dereferencing type-punned pointer will
> |  break strict-aliasing rules
> | 

[ Note:  Back from one month out of office ]

Thanks for the heads up.  I cannot reproduce -- perhaps my gcc is out
of date -- will update to Debian unstable and retry.

> | C99 language semantics now assume that pointers to different types
> | point to different memory locations, which is obvious nonsense, but
> | part of the new standard.
> 
> That statement is obviously untrue. 
> 
> The non-aliasing rule, which has always been there since I don't know
> when -- certainly, it is part of C89, and it is not a C99 invention --
> says that the following is undefined behaviour
> 
>       double z;
>       *(long*)&z = 1;
>       printf ("%g", z);
> 
> That makes perfect sense.  Why would you think it is nonsense?
> 
> | You might want to add -fno-strict-aliasing option to the GCC command line.
> 
> Instead of papering over the incorrectness, I would suggest to fix it.
> 

Agreed.

Take care,

> -- Gaby
> 
> 
> 

-- 
Camm Maguire                                            address@hidden
==========================================================================
"The earth is but one country, and mankind its citizens."  --  Baha'u'llah




reply via email to

[Prev in Thread] Current Thread [Next in Thread]