[Mesa-dev] [PATCH] docs/autoconf: mention CC/CXX when doing multilib builds

[Emil Velikov]

On 13/08/14 23:01, Ilia Mirkin wrote:
> On Wed, Aug 13, 2014 at 5:56 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>> On 13/08/14 22:22, Ilia Mirkin wrote:
>>> On Wed, Aug 13, 2014 at 5:16 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>>>> Signed-off-by: Emil Velikov <emil.l.velikov at gmail.com>
>>>> ---
>>>>
>>>> Unless someone object I would like to squash this patch with the
>>>> previous one.
>>>>
>>>> -Emil
>>>>
>>>>  docs/autoconf.html | 16 ++++++++++++++--
>>>>  1 file changed, 14 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/docs/autoconf.html b/docs/autoconf.html
>>>> index f27838f..c225659 100644
>>>> --- a/docs/autoconf.html
>>>> +++ b/docs/autoconf.html
>>>> @@ -141,14 +141,26 @@ assembly will not be used.</p>
>>>>  <dt><code>--host=</code></dt>
>>>>  <dd><p>By default, the build will compile code for the architecture that
>>>>  it's running on. In order to build Mesa on a x64-86 machine that is to run
>>>
>>> While you're fixing stuff, x86-64
>>>
>> Ack, will do.
>>
>>>> -on a i686, one would need to set the options to:
>>>> +on a i686, one would need to set the options to:</p>
>>>>
>>>>  <p><code>--build=i686-pc-linux-gnu --host=i686-pc-linux-gnu</code></p>
>>>>
>>>>  Note that these can vary from distribution to distribution. For more
>>>>  information check with the
>>>>  <a href="https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/Specifying-Target-Triplets.html">
>>>> -autoconf manual</a>.</p>
>>>> +autoconf manual</a>.
>>>> +
>>>> +
>>>> +<p>In some cases a single compiler is capable of handling both architectures
>>>> +in that case one would need to set the <code>CC,CXX</code> variables
>>>> +appending the correct machine options. Seek your compiler documentation for
>>>> +further information -
>>>> +<a href="https://gcc.gnu.org/onlinedocs/gcc/Submodel-Options.html"> gcc
>>>> +machine dependent options</a></p>
>>>> +
>>>> +<p>The following is the complete setup needed to compile on my Archlinux setup</p>
>>>
>>> There's nothing about the below that's specific to Arch, or any
>>> distro, really -- I'd avoid the explicit distro reference.
>> Haven't touched any other distro but Arch in years. Yet it makes sense to drop
>> the distro reference but keep the example.
> 
> Right, I was suggesting s/Archlinux// :)
> 
>>
>>> Do you
>>> actually need the --build and --host things? I thought that was if you
>>> were going to use a cross-compiler. I only have
>>> x86_64-pc-linux-gnu-gcc, no i686-...-gnu-gcc.
>>>
>> --build/host (at lest) used to be required by mesa, as some bits were built
>> differently when doing cross-compilation. Not sure what the case is now - I
>> care not look in src/{glsl,mesa} which is where all of that chaos was.
> 
> But that's my point -- it's not a cross-compilation. It's using the
> same system compiler. The way cross-compilation works (afaik) is that
> you just look for $host-gcc, $host-ld, $host-as etc (and use
> $build-gcc, etc for the binaries that need to be run as part of the
> build). But i686-...-gcc is not a binary available on my system. So
> the cross-compilation will fail...
> 
IIRC the --build/host flags were required to get mesa past the "make" into the
"make check" stage when doing "multilib" builds. Things may have changed, yet
there should be no side-effects (unless we have a bug somewhere). Will give it
a try shortly, perhaps you can give it a bash on your Gentoo system as well ?

Afaik if $arch-$plat-gcc is missing, then we fall back to $arch-gcc and
finally to gcc, and similarly for every other tool used.

> Perhaps I'm just misunderstanding how things work though.
I don't claim to be an expert on the topic so it may be that I'm missing
something :)

-Emil
> 
>>
>>
>>> In the past I've just done CFLAGS=-m32 CXXFLAGS=-m32 and it has worked
>>> like a charm. But perhaps there's a downside to doing that...
>>>
>> I cannot think of any side effects to be honest (barring any bugs in mesa).
>> Yet I would love if people avoid touching any *FLAGS :)
>>
>> Thanks
>> -Emil
>>
>>>> +
>>>> +<code>./configure CC="gcc -m32" CXX="g++ -m32" --build=i686-unknown-linux-gnu --host=i686-unknown-linux-gnu ...</code>
>>>>  </dd>
>>>>  </dl>
>>>>
>>>> --
>>>> 2.0.2
>>>>
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>>