[Mesa-dev] [PATCH] configure.ac: Add --with-wayland-scanner-path

[Emil Velikov]

On 26 May 2017 at 08:52, Jussi Kukkonen <jussi.kukkonen at intel.com> wrote:
>
>
> On 24 May 2017 at 16:39, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>>
>> Hi Jussi,
>>
>> On 23 May 2017 at 09:13, Jussi Kukkonen <jussi.kukkonen at intel.com> wrote:
>> > Modify wayland-scanner lookup: Use the path given by pkg-config
>> > but offer an option to override the path with
>> > "--with-wayland-scanner-path=PATH". The latter is useful for
>> > cross-compile situations.
>> >
>> > AC_PATH_PROG is no longer used (if the scanner is installed it should
>> > get found by pkg-config). AC_SUBST is added so the output variable is
>> > created when only the configure option is used.
>> > ---
>> >
>> > My goal is to standardize wayland-scanner usage in a way that does not
>> > require patching when cross-compiling in Yocto (the detailed issue is
>> > that in Yocto pkg-config will return a "wayland_scanner" variable but
>> > that will contain a _target path_ when we would like to use a native
>> > sysroot path instead).
>> >
>> > I've sent a similar patch to weston and intend to fix other projects
>> > if these two patches are well received.
>> >
>> I might have misread something, but on a quick look the patch does not
>> look quite right. Stepping aside for a moment,
>>
>> Can you explain clearly what's happening/wrong in the whole scenario?
>>  - Yocto does has A stage where it does X.
>>  - Then it proceeds to B... at which point $file
>> foo/wayland-scanner.pc gets picked
>>  - That results in an error due to variable containing $bar, due to
>> the $step above
>
> Hi Emil,
>
> I'm hoping this is a coherent enough explanation of the issue...
>
> When yocto cross-compiles mesa for target, we already have
>   a) All dependency headers and libraries in a target sysroot
>   b) Native wayland-scanner in a native sysroot
>
> The problem as I see it is that there is no way to express the _native_
> sysroot in pkg-config: PKG_CONFIG_SYSROOT_DIR and pc_sysroot_dir logically
> refer to the target sysroot. So when mesa configure does "pkg-config
> --variable=wayland_scanner wayland-scanner" it gets a reasonable
> "/usr/bin/wayland-scanner" response: this would be the correct path to
> wayland-scanner on _target_. In the best case this fails during compile when
> the scanner isn't found but unfortunately /usr/bin/wayland-scanner is often
> also a valid path to _host_ wayland-scanner which might be from a completely
> different and unrelated wayland version...
>
Barring an important s/pkg-config/$PKG_CONFIG/ I think I agree here.

AFAICT there are a couple of alternative solutions - have you
considered/tried any of them?

a) w/o a wrapper script
$ export PKG_CONFIG_PATH= // you need this if using the system
pkgo-config. if the local/native one is used, this should be optional
$ export PKG_CONFIG_LIBDIR=$path_to_non_system_host_pkgconfig:${SYSROOT}/usr/{lib,share}/pkgconfig
$ export PKG_CONFIG_SYSROOT_DIR=${SYSROOT}

b) with a wrapper script - see [1].
I think that the "export PKG_CONFIG_DIR=" is a typo (should be ..PATH
instead) and is not strictly required - feel free to check either way.
Note that the exec at the end might need to be amended to
/path/to/$(CHOST)-pkg-config.

Thanks
Emil

[1] https://autotools.io/pkgconfig/cross-compiling.html