[Buildroot] [RFC v1] libv4l: build utils only on MMU (with fork support) platforms
Peter Seiderer
ps.report at gmx.net
Mon Jul 17 18:09:01 UTC 2017
Hello Hugues,
On Mon, 17 Jul 2017 10:07:07 +0000, Hugues FRUCHET <hugues.fruchet at st.com> wrote:
> Hi Peter,
>
> I have tested on STM32 platform running Cortex F family having no MMU,
> shared libraries are disabled (no dlopen) and no fork supported on our
> setup.
>
> libv4lconvert should not have been built at all, because entire lib/
> folder build is conditional to shared library support:
> * configure.ac
> AM_CONDITIONAL([WITH_LIBV4L], [test x$enable_libv4l != xno -a
> x$enable_shared != xno])
> * Makefile.am
> [...]
> +if WITH_LIBV4L
> +SUBDIRS += lib
> +endif
A little bit confused, one of the patches you introduced changed it to:
- without WITH_LIBV4L: no libv4l libraries at all
- without WITH_DYN_LIBV4L: only static libraries, no dynamic libraries
And from configure --help:
--disable-libv4l disable libv4l compilation
--disable-dyn-libv4l disable dynamic libv4l support
>
> But checking your log I see that --enable-shared is set, so it seems
> that you are supporting shared libraries on no-MMU platform but without
> fork() support, is my understanding correct ?
>
Yes...
> What you can do to fix build is to force disabling of libs inside libv4l
> package:
>
> package/libv4l/libv4l.mk
> +ifeq ($(BR2_USE_MMU),)
> +LIBV4L_CONF_OPTS += --disable-libv4l
> +endif
Works, but feels wrong: A package named libv4l enabled and building/installing
nothing (except when LIBV4L_UTILS is enabled)...
Regards,
Peter
>
> Hoping that helps.
>
> Best regards,
> Hugues.
>
> On 07/11/2017 07:26 PM, Peter Seiderer wrote:
> > Fixes [1]:
> >
> > CXXLD v4l2-compliance
> > .../output/build/libv4l-1.12.5/lib/libv4lconvert/.libs/libv4lconvert.so: undefined reference to `fork'
> > collect2: error: ld returned 1 exit status
> >
> > [1] http://autobuild.buildroot.net/results/7e8/7e8fbd99a8c091d7bbeedd16066297682bbe29fe
> >
> > Signed-off-by: Peter Seiderer <ps.report at gmx.net>
> > ---
> > The libv4l build for noMMU platforms was enabled with commit 'package/libv4l:
> > allow build of v4l2 utilities on noMMU platforms' (see [2]). But libv4lconvert uses
> > fork internally, so all utils linking against fail to build. Fix this by disabling
> > the utils on noMMU platforms (so keep building all libraries).
> >
> > Alternatives would be:
> >
> > - disable libv4l on all noMMU platforms (not only the utils), revert a part
> > of commit [2]
> >
> > - create a patch to disable only libv4lconvert (and all dependend utils)
> > on noMMU platforms
> >
> > [2] https://git.buildroot.net/buildroot/commit/?id=f837251785e9389f53d695ddb8a094707865171b
> > ---
> > package/libv4l/Config.in | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/package/libv4l/Config.in b/package/libv4l/Config.in
> > index e7f78dc70f..61c290f251 100644
> > --- a/package/libv4l/Config.in
> > +++ b/package/libv4l/Config.in
> > @@ -19,6 +19,7 @@ comment "libv4l JPEG support not enabled"
> >
> > config BR2_PACKAGE_LIBV4L_UTILS
> > bool "v4l-utils tools"
> > + depends on BR2_USE_MMU # fork(), used in libv4lconvert linked by various utils eg. v4l2-compliance
> > help
> > v4l-utils is a collection of various video4linux and DVB utilities.
> > Enable this if you want to build the following tools:
> >
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