[dpdk-dev] [PATCH 0/6] next-build: create both static and shared libs

[Luca Boccassi]

On Tue, 2017-12-12 at 17:14 +0000, Bruce Richardson wrote:
> On Tue, Dec 12, 2017 at 04:59:34PM +0000, Bruce Richardson wrote:
> > This patchset changes the meson+ninja build system to always create
> > both
> > static and shared libraries when doing a build. The applications
> > compiled
> > as part of a build use either the shared or static libraries
> > depending on
> > what the default_library build setting is.
> > 
> > NOTE:
> > The main difficulty with this change is adjusting the pkgconfig
> > file so
> > that external apps, like the examples, can be built using either
> > the static
> > or shared libraries. One of the key issues was the fact that
> > running
> > "pkg-config --static --libs libdpdk" outputs first the normal libs,
> > and
> > then the extra static ones. This is a problem because the driver
> > libs are
> > for static only builds, but need to come before, not after the
> > standard
> > DDPK libraries.  It also procludes adding in the -Wl,-Bstatic flag
> > into the output for the standard libraries to link them statically.
> > 
> > There were two options considered for mananging the pkg-config
> > settings.
> > 1. Creating a separate .pc file for static builds with exactly the
> > flags
> > needed.
> > 2. Modifying the single .pc file so that it was "good enough" to
> > enable
> > static builds without too much work.
> > 
> > For this version of this set, I took option #2. To link using
> > dynamic libs,
> > all is as normal, to use static libs, the user needs to prepend
> > "-Wl,-Bstatic" before the "pkgconfig --static" library output. This
> > can be
> > seen in the changes to the example application makefiles, which now
> > support
> > building the examples using shared or static DPDK libs.
> > 
> 
> Just to emphasise that I'm looking for input into whether I took the
> right choice here. Option #1 has some advantages in that we can tune
> the
> output specifically for the static build case, but I wasn't sure
> whether
> it would be the done thing to have two different .pc files for a
> single
> package. Feedback from packagers welcome!
> 
> /Bruce

I don't link #1 too much - too "special". I think an additional flag is
more friendly.

A good solution would be a Cflags.private feature, sadly that is not
supported by pkgconfig despite many requests for it.

A possible way to sugar-coat it could be to add a custom variable, and
then instruct the users to do something like:

$(shell pkg-config --variable=ldflags.static libdpdk) $(shell pkg-
config --static --libs libdpdk)

Unfortunately, again, --variable cannot be used together with --libs in
the same call.

-- 
Kind regards,
Luca Boccassi