Re: Aliasing violations in gnu_java_nio_VMChannel.c

2009/10/23 Andrew Haley <[email protected]>:
> Andrew John Hughes wrote:
>> 2009/10/22 Andrew Haley <[email protected]>:
>>> This:
>>>
>>>
>>> #ifdef HAVE_GETPEERNAME
>>> #ifdef HAVE_INET6
>>>  struct sockaddr_in6 *addr6;
>>>  struct sockaddr_in6 sock_storage;
>>>  socklen_t socklen = sizeof (struct sockaddr_in6);
>>> #else
>>>  struct sockaddr_in sock_storage;
>>>  socklen_t socklen = sizeof (struct sockaddr_in);
>>> #endif /* HAVE_INET6 */
>>>
>>>  struct sockaddr *sockaddr = (struct sockaddr *) &sock_storage;
>>>
>>>
>>> is clearly an aliasing violation: sock_storage is of type struct sockaddr_in6,
>>> and *sockaddr is of type struct sockaddr.
>>>
>>> It would be easy enough to fix the code with a union, but I can't test it
>>> because gcj doesn't use this code.  I could simply compile with
>>> -fno-strict-aliasing.
>>>
>>> Thoughts?
>>>
>>> Andrew.
>>>
>>>
>>
>> I posted a patch sometime ago to do exactly that (use a union), but
>> received no response:
>>
>> http://developer.classpath.org/pipermail/classpath-patches/2009-June/006341.html
>>
>> It does need more testing than I've had chance to give it so far, I
>> just haven't had time to do any more work on it.
>
> I seriously wonder if it's worth the effort.  I just did this:
>
> Index: configure.ac
> ===================================================================
> RCS file: /sources/classpath/classpath/configure.ac,v
> retrieving revision 1.244
> diff -c -u -r1.244 configure.ac
> --- configure.ac        6 Feb 2009 02:21:23 -0000       1.244
> +++ configure.ac        23 Oct 2009 09:10:33 -0000
> @@ -514,7 +514,7 @@
>     dnl CFLAGS that are used for all native code.  We want to compile
>     dnl everything with unwinder data so that backtrace() will always
>     dnl work.
> -    EXTRA_CFLAGS='-fexceptions -fasynchronous-unwind-tables'
> +    EXTRA_CFLAGS='-fexceptions -fasynchronous-unwind-tables -fno-strict-aliasing'
>     AC_SUBST(EXTRA_CFLAGS)
>
>     dnl Strict warning flags which not every module uses.
>
> which is a much safer change.  It will somewhat pessimize other native code,
> that's true, but will that make any real difference to anyone these days?
>
> Andrew.
>

Why not just amend the CFLAGS in the local Makefile.am for cpnet?
-- 
Andrew :-)

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