Re: An aliasing problem

[Sam S. <sd...@gn...>]

Hi Bruno,

> * Bruno Haible <oe...@py...t> [2017-02-27 22:36:07 +0100]:
>
>> diff -r 208ade5c97ca src/makemake.in
>> --- a/src/makemake.in	Sun Feb 26 20:07:47 2017 -0500
>> +++ b/src/makemake.in	Mon Feb 27 13:05:45 2017 -0500
>> @@ -1335,13 +1335,12 @@ fi
>>  # specific compiler options. I prefer to do it through compiler options.
>>  if [ $XCC_GCC = true ] ; then
>>    XCFLAGS=$XCFLAGS' -fno-strict-aliasing'
>> -else
>> -  if [ "$HSYSOS" = aix ] ; then # for xlc
>> +elif [ "$HSYSOS" = aix ] ; then # for xlc
>>      XCFLAGS=$XCFLAGS' -qalias=noansi'
>> -  fi
>> -  if [ -n "$XCC_SUNPRO" ] ; then # for SUNWspro cc
>> +elif [ -n "$XCC_SUNPRO" ] ; then # for SUNWspro cc
>>      XCFLAGS=$XCFLAGS' -xalias_level=weak'
>> -  fi
>> +elif [ "${with_debug}" != no ]; then
>> +  echo "$0: WARNING: how to disable strict aliasing with ${XCC} on ${HSYSOS}?" >&2
>>  fi
>>  
>>  if [ "${with_dynamic_modules}" != no ]; then # not on msvc
>
> The users of the configure script are most often our users, not ourselves,
> therefore such a warning it not very helpful.

On a second thought, this appears like a clear case for an autoconf test:
check whether the default compiler does strict aliasing optimizations
and, if it does, try to disable them, and if we cannot disable them,
fail configure.


-- 
Sam Steingold (http://sds.podval.org/) on darwin Ns 10.3.1504
http://steingoldpsychology.com http://www.childpsy.net https://jihadwatch.org
http://www.dhimmitude.org http://www.memritv.org http://islamexposedonline.com
There are two ways to win an argument with a woman.  Neither works.