Vlastimil Babka wrote:
> Peter Gordon wrote:
>> On Tue, 2007-07-17 at 19:47 -0400, Mike Frysinger wrote:
>>> historically, gcc on x86 has always defaulted to i386. some people noticed
>>> recently that glibc-2.6 fails to build in this situation as they were only
>>> setting -mtune via CFLAGS, not -march. i'll be tweaking gcc so that it
>>> will
>>> default -march based on your CHOST. so all the i686-* people will now have
>>> a
>>> default -march=i686 implied in their gcc systems, i586-* people will
>>> have -march=i586, etc... keep in mind this is merely the default.
>>> -mike
>> Does this mean that any user-set "-march" flag is overridden for these
>> cases? Just curious.
>
> I think he meant CHOST sets just *default* so any user-set -march
> overrides that.
> But I wonder what happens to user-set -mtune then? Since AFAIK -march
> implies -mtune, will also the default -march override user-set -mtune?
Previously GCC defaulted to -march=i386, which implied -mtune=i386
(actually, -mcpu for some reason (?)), when neither were set. People
are setting CFLAGS="-mtune=pentium4 -O2 -fblah..." which therefore is
defaulting to -march=i386 -mtune=pentium4. glibc-2.6 requires >=
-march=i486. Kaboom.
Now -march=$(echo $CHOST | awk -F- '{ print $1 }'), which implies
-mtune=echo $CHOST | awk -F- '{ print $1 }' when neither are set. If
_either_ are set by the user, they are overridden.
ie. you can still set -march=i386 or -mtune=i386 or whatever you like.
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