[dpdk-dev] [dpdk-stable] [PATCH 2/2] build: use dependency() instead of find_library()

[Bruce Richardson]

On Fri, Jan 11, 2019 at 02:56:28PM +0000, Luca Boccassi wrote:
> On Fri, 2019-01-11 at 14:24 +0000, Bruce Richardson wrote:
> > On Fri, Jan 11, 2019 at 12:39:23PM +0000, Luca Boccassi wrote:
> > > On Fri, 2019-01-11 at 11:52 +0000, Bruce Richardson wrote:
> > > > On Fri, Jan 11, 2019 at 11:10:28AM +0000, Luca Boccassi wrote:
> > > > > On Mon, 2019-01-07 at 16:55 +0000, Bruce Richardson wrote:
> > > > > > On Mon, Jan 07, 2019 at 04:39:34PM +0000, Luca Boccassi
> > > > > > wrote:
> > > > > > > On Mon, 2019-01-07 at 14:28 +0000, Bruce Richardson wrote:
> > > > > > > > On Thu, Jan 03, 2019 at 06:57:25PM +0100, Luca Boccassi
> > > > > > > > wrote:
> > > > > > > > > For libbsd, which is checked in a top level file and
> > > > > > > > > used
> > > > > > > > > to be
> > > > > > > > > added
> > > > > > > > > to the global linker flags array, add it to the
> > > > > > > > > ext_deps
> > > > > > > > > array
> > > > > > > > > of
> > > > > > > > > all top level meson files (app, test, lib, examples,
> > > > > > > > > drivers).
> > > > > > > > > The
> > > > > > > > > most correct change would be to let each individual
> > > > > > > > > library/driver/app
> > > > > > > > > depend on it individually if they use symbols from it,
> > > > > > > > > but
> > > > > > > > > it
> > > > > > > > > would
> > > > > > > > > diverge from the legacy Makefile's behaviour and make
> > > > > > > > > life
> > > > > > > > > a
> > > > > > > > > bit
> > > > > > > > > more
> > > > > > > > > difficult for contributors.
> > > > > > > > 
> > > > > > > > It shouldn't be necessary to add libbsd as a dependency
> > > > > > > > for
> > > > > > > > everything. I
> > > > > > > > think just adding it as a dependency of EAL should work
> > > > > > > > fine. 
> > > > > > > 
> > > > > > > Won't that mean that the shared libraries other than EAL
> > > > > > > will
> > > > > > > have
> > > > > > > undefined references?
> > > > > > 
> > > > > > Should not happen. AFAIK when you link against a library in
> > > > > > meson
> > > > > > it
> > > > > > will
> > > > > > also link against any of that libraries dependencies too. For
> > > > > > shared
> > > > > > libraries meson always disallowed undefined references in the
> > > > > > linker
> > > > > > commandline. [To have libs with undefined refs, e.g. plugins,
> > > > > > you
> > > > > > need to
> > > > > > use "shared_module" rather than "shared_library" command].
> > > > > 
> > > > > Looked at this again, and rte_cmdline is using strlcpy as well,
> > > > > and
> > > > > it's built before rte_eal, so it fails:
> > > > > 
> > > > > lib/76b5a35@@rte_cmdline at sta/librte_cmdline_cmdline_parse.c.o:
> > > > > In
> > > > > function `cmdline_complete':
> > > > > cmdline_parse.c:(.text+0x861): undefined reference to `strlcpy'
> > > > > 
> > > > > Adding it to ext_deps in both rte_cmdline and rte_eal works. Is
> > > > > that an acceptable compromise?
> > > > > 
> > > > 
> > > > Sure. If eal has a dependency on cmdline, you probably don't need
> > > > to
> > > > add it
> > > > as an external dependency to EAL too, but it doesn't really hurt
> > > > to
> > > > do so.
> > > > 
> > > > /Bruce
> > > 
> > > eal does not depend on cmdline, so added in both in v2. I also
> > > split
> > > the libbsd change and meson bump to 0.47.1 in a separate commit in
> > > the
> > > series.
> > > 
> > > -- 
> > 
> > If there is no dependency, why is it being built first?
> 
> Comment says "ethdev depends on cmdline for parsing functions"
> 
> https://git.dpdk.org/dpdk/tree/lib/meson.build#n12
> 
> -- 
So it looks like it could be placed between EAL and ethdev. Not a bit deal
either way, so I'm happy enough to leave it as-is for now.

/Bruce