[libcamera-devel] [PATCH] libcamera: add dependencies to libcamera_dep

[Fabrice Fontaine]

Dear Laurent,

Le mer. 2 juin 2021 à 02:59, Laurent Pinchart
<laurent.pinchart at ideasonboard.com> a écrit :
>
> Hi Fabrice,
>
> Thank you for the patch.
>
> On Tue, Jun 01, 2021 at 10:51:54PM +0200, Fabrice Fontaine wrote:
> > Add dependencies to libcamera_dep to avoid the following build failure
> > with qcam on sparc v8 which is raised since commit
> > a8310248fc26cc1e1b791af5e9394c1d20bee269:
> >
> > FAILED: src/qcam/qcam
> > /srv/storage/autobuild/run/instance-0/output-1/host/bin/sparc-linux-g++  -o src/qcam/qcam src/qcam/qcam.p/meson-generated_.._qt5-feathericons_qrc.cpp.o src/qcam/qcam.p/meson-generated_moc_main_window.cpp.o src/qcam/qcam.p/meson-generated_moc_viewfinder_qt.cpp.o src/qcam/qcam.p/.._cam_options.cpp.o src/qcam/qcam.p/.._cam_stream_options.cpp.o src/qcam/qcam.p/format_converter.cpp.o src/qcam/qcam.p/main.cpp.o src/qcam/qcam.p/main_window.cpp.o src/qcam/qcam.p/message_handler.cpp.o src/qcam/qcam.p/viewfinder_qt.cpp.o src/qcam/qcam.p/dng_writer.cpp.o -Wl,--as-needed -Wl,--no-undefined -Wl,-O1 -Wshadow -include config.h '-Wl,-rpath,$ORIGIN/../libcamera' -Wl,-rpath-link,/srv/storage/autobuild/run/instance-0/output-1/build/libcamera-3a1f67a8031ac5ad96a11d5dc8b2e8976290497b/build/src/libcamera -Wl,--start-group src/libcamera/libcamera.so /srv/storage/autobuild/run/instance-0/output-1/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib/libQt5Core.so /srv/storage/autobuild/run/instance-0/output-1/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib/libQt5Gui.so /srv/storage/autobuild/run/instance-0/output-1/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib/libQt5Widgets.so /srv/storage/autobuild/run/instance-0/output-1/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib/libtiff.so -Wl,--end-group
> > /srv/storage/autobuild/run/instance-0/output-1/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/9.3.0/../../../../sparc-buildroot-linux-uclibc/bin/ld: src/qcam/qcam.p/main_window.cpp.o: undefined reference to symbol '__atomic_fetch_add_4@@LIBATOMIC_1.0'
> > /srv/storage/autobuild/run/instance-0/output-1/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/9.3.0/../../../../sparc-buildroot-linux-uclibc/bin/ld: /srv/storage/autobuild/run/instance-0/output-1/host/sparc-buildroot-linux-uclibc/sysroot/lib/libatomic.so.1: error adding symbols: DSO missing from command line
>
> There's something that puzzles me, maybe you can enlighten me.
>
> libcamera uses atomic operations internally, which, one some platforms,
> require linking against libatomic. As a result, we add libatomic to
> libcamera_deps (as an optional depedency), so libcamera.so is linked
> against libatomic.so. So far, so good. Why do we need applications that
> link against libcamera to also link against libatomic, if they don't use
> atomic operations directly themselves ?
I would say that this is mandatory when building statically but static
build is disabled with libcamera on buildroot due to gnutls.
It seems that __atomic_fetch_add_4 is used by main_window.cpp., here
is the result of grep:

grep -r __atomic_fetch_add_4
output/build/libcamera-3a1f67a8031ac5ad96a11d5dc8b2e8976290497b/
grep: output/build/libcamera-3a1f67a8031ac5ad96a11d5dc8b2e8976290497b/build/src/qcam/qcam.p/main_window.cpp.o:
binary file matches
grep: output/build/libcamera-3a1f67a8031ac5ad96a11d5dc8b2e8976290497b/build/src/libcamera/libcamera.so:
binary file matches
grep: output/build/libcamera-3a1f67a8031ac5ad96a11d5dc8b2e8976290497b/build/src/libcamera/libcamera.so.p/message.cpp.o:
binary file matches

atomic is probably pulled in because of std::shared_ptr which is used
by qcam since its addition in commit
97e8b3a2eb321884fe1e15fb584f41a38cc33d51:
https://en.cppreference.com/w/cpp/memory/shared_ptr.
So I would suggest to just add libatomic dependency to qcam.
>
> > Fixes:
> >  - http://autobuild.buildroot.org/results/d0726b2253f1f3d006e057f3b32c646c4b9b5f7a
> >
> > Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>
> > ---
> >  src/libcamera/meson.build | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
> > index cc2b8669..af3533ad 100644
> > --- a/src/libcamera/meson.build
> > +++ b/src/libcamera/meson.build
> > @@ -160,6 +160,7 @@ libcamera_dep = declare_dependency(sources : [
> >                                         libcamera_public_headers,
> >                                     ],
> >                                     include_directories : libcamera_includes,
> > +                                   dependencies : libcamera_deps,
> >                                     link_with : libcamera)
> >
> >  subdir('proxy/worker')
>
> --
> Regards,
>
> Laurent Pinchart
Best Regards,

Fabrice