[PATCH xserver 1/3] config: add -fno-strict-aliasing now that it is out of $CWARNFLAGS

[Jeremy Huddleston]

On Feb 24, 2010, at 05:45, Gaetan Nadon wrote:

> On Wed, 2010-02-24 at 09:34 +0100, Michel Dänzer wrote:
> 
>> On Tue, 2010-02-23 at 11:11 -0800, Jeremy Huddleston wrote: 
>>> On Feb 23, 2010, at 11:07, Keith Packard wrote:
>>> 
>>>> On Tue, 23 Feb 2010 13:37:18 -0500, Gaetan Nadon  
>>>> <memsize at videotron.ca> wrote:
>>>> 
>>>>> This patch will ensure the xserver continues to suppress the
>>>>> optimization, based on strict aliasing rules, after the option
>>>>> is removed from $CWARNFLAGS. There is no change in the object
>>>>> code produced.
>>>> 
>>>> I don't think we need to allow any of the code in the X server to be
>>>> 'optimized' in this fashion, so I don't see a need to allow for
>>>> per-directory selection.
>>> 
>>> It would be helpful if I had the option to remove this flag from  
>>> XQuartz.
>> 
>> Out of curiosity, what significant benefit have you measured from using
>> -fstrict-aliasing?
>> 
>> 
> 
> Excellent question which I carefully want to avoid :-) 
> 
> The problem I want to solve is the following: someone added
> -fnostrict-aliasing a long time ago and I don't know why. Then it got
> copied to a number of libraries, then got included in a macro
> (XORG_CWARNFLAGS), which then got included by over a hundred modules,
> still not knowing why.
> 
> There are over 50 modules that are compiling with no warning flags at
> all. I don't want to contribute to the spread of this option. The patch
> is about *transferring* the option out of the macro back to the modules
> (where the skills are) and let them decide if they want that option or
> not.

Additionally, before being copied into XORG_CWARNFLAGS fairly recently, this was only in a handful of modules:

libICE
libSM
libX11
libXau
libXfont
libXft
libXpm
libXres
xorg-server
(I didn't check xf86-drivers)

So adding it across the board is rather far-reaching, IMO.  I believe it should only be added back to the modules listed above.

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