Re: [dpdk-dev] [PATCH] build: support i686 target on x86 64-bit hosts

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 9/25/2020 3:28 PM, Bruce Richardson wrote:
> On Fri, Sep 25, 2020 at 10:08:35AM -0400, Lance Richardson wrote:
>> On Fri, Sep 25, 2020 at 9:44 AM Bruce Richardson
>> <bruce.richardson@intel.com> wrote:
>>>
>>> On Fri, Sep 25, 2020 at 09:27:25AM -0400, Lance Richardson wrote:
>>>> On Fri, Sep 25, 2020 at 5:13 AM Bruce Richardson
>>>> <bruce.richardson@intel.com> wrote:
>>>>>
>>>>> On Thu, Sep 24, 2020 at 12:37:42PM -0400, Lance Richardson wrote:
>>>>>> Add meson cross files for building i686 targets using gcc on x86_64
>>>>>> linux hosts.
>>>>>>
>>>>>> Uusage example:
>>>>>>
>>>>>>      meson --cross-file config/x86/cross-i686-linux-gcc build-i686
>>>>>>      ninja -C build-i686
>>>>>>
>>>>>> Signed-off-by: Lance Richardson <lance.richardson@broadcom.com>
>>>>>> ---
>>>>>> Red Hat distros use a different name for the 32-bit pkg-config
>>>>>> command from most other distros, maybe there is a better way
>>>>>> to handle this than using separate files.
>>>>>>
>>>>>> Others will probably have better naming suggestions for the files.
>>>>>>
>>>>> Just to note that rather than using cross-files, building i686 on x86_64
>>>>> should be possible by just setting environment variables.
>>>>>
>>>>> For example, on Ubuntu 20.04, this works for me:
>>>>>
>>>>> PKG_CONFIG_LIBDIR=/usr/lib/i386-linux-gnu/pkgconfig CFLAGS='-m32' LDFLAGS='-m32' meson --werror build-32bit
>>>>> ninja -C build-32bit/
>>>>>
>>>>> For Fedora or Redhat system the PKG_CONFIG_LIBDIR will be different (I
>>>>> think just /usr/lib/pkgconfig), but the rest should work identically.
>>>>>
>>>>> /Bruce
>>>>
>>>> Thanks, that does work, although I'll have some trouble remembering it
>>>> for future
>>>> use (unlike using cross-files). Googling for "PKG_CONFIG_LIBDIR meson dpdk"
>>>> did lead me to this discussion, which makes it sound like cross-files
>>>> might still
>>>> worthy of consideration:
>>>>
>>>>     https://patches.dpdk.org/patch/69067/
>>>>
>>>
>>> Yes, absolutely the cross-file is worthy of consideration. The most awkward
>>> part in both cases is getting the 32-bit pkg-config right.
>>
>> Agreed, having the distro-specific bits is not pretty.
>>
>> Would it be possible to set the pkgconfig binary name or
>> PKG_CONFIG_LIBDIR in config/x86/meson.build? If so,
>> maybe we could have a single cross-file and probe for the
>> distro-specifics in meson.build.
> 
> Sadly, I'm not aware of any way to do that right now. It probably requires
> changes in meson itself. :-(
> 

I did hit similar thing with arm cross compile recently, the values 
provided in the 'config/arm/arm64_armv8_linux_gcc' doesn't match with 
the cross compiler I installed, so had to update it manually.
Not sure if it is possible to cover all options, or should we add a 
config file to cover each case, perhaps we can document it and go with 
common values.