Re: [dpdk-dev] [PATCH v3 2/4] build: use dependency() instead of find_library()

[Luca Boccassi <bluca@debian.org>]

On Fri, 2019-01-11 at 17:21 +0000, Bruce Richardson wrote:
> On Fri, Jan 11, 2019 at 04:26:06PM +0000, Luca Boccassi wrote:
> > Whenever possible (if the library ships a pkg-config file) use
> > meson's
> > dependency() function to look for it, as it will automatically add
> > it
> > to the Requires.private list if needed, to allow for static builds
> > to
> > succeed for reverse dependencies of DPDK. Otherwise the recursive
> > dependencies are not parsed, and users doing static builds have to
> > resolve them manually by themselves.
> > When using this API avoid additional checks that are superfluos and
> 
> Spelling: superfluous

I _always_ get that one wrong :-)

> > take extra time, and avoid adding the linker flag manually which
> > causes
> > it to be duplicated.
> > 
> > Signed-off-by: Luca Boccassi <bluca@debian.org>
> > ---
> > v2: split libbsd change in a separate commit, remove CC to stable
> >     as a meson bump will be required
> > 
> >  drivers/crypto/ccp/meson.build     | 1 -
> >  drivers/crypto/openssl/meson.build | 1 -
> >  drivers/crypto/qat/meson.build     | 1 -
> >  drivers/meson.build                | 2 +-
> >  drivers/net/bnx2x/meson.build      | 2 +-
> >  drivers/net/mlx4/meson.build       | 6 +++---
> >  drivers/net/mlx5/meson.build       | 6 +++---
> >  drivers/net/pcap/meson.build       | 5 ++---
> >  lib/librte_bpf/meson.build         | 4 ++--
> >  lib/librte_telemetry/meson.build   | 2 +-
> >  10 files changed, 13 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/crypto/ccp/meson.build
> > b/drivers/crypto/ccp/meson.build
> > index e43b00591..915c4c854 100644
> > --- a/drivers/crypto/ccp/meson.build
> > +++ b/drivers/crypto/ccp/meson.build
> > @@ -18,4 +18,3 @@ sources = files('rte_ccp_pmd.c',
> >  		'ccp_pmd_ops.c')
> >  
> >  ext_deps += dep
> > -pkgconfig_extra_libs += '-lcrypto'
> > diff --git a/drivers/crypto/openssl/meson.build
> > b/drivers/crypto/openssl/meson.build
> > index c2a0dd8ba..80e5e8835 100644
> > --- a/drivers/crypto/openssl/meson.build
> > +++ b/drivers/crypto/openssl/meson.build
> > @@ -8,4 +8,3 @@ endif
> >  deps += 'bus_vdev'
> >  sources = files('rte_openssl_pmd.c', 'rte_openssl_pmd_ops.c')
> >  ext_deps += dep
> > -pkgconfig_extra_libs += '-lcrypto'
> > diff --git a/drivers/crypto/qat/meson.build
> > b/drivers/crypto/qat/meson.build
> > index 9cc98d2c2..21f969735 100644
> > --- a/drivers/crypto/qat/meson.build
> > +++ b/drivers/crypto/qat/meson.build
> > @@ -13,6 +13,5 @@ if dep.found()
> >  			     'qat_sym.c',
> >  			     'qat_sym_session.c')
> >  	qat_ext_deps += dep
> > -	pkgconfig_extra_libs += '-lcrypto'
> >  	qat_cflags += '-DBUILD_QAT_SYM'
> >  endif
> > diff --git a/drivers/meson.build b/drivers/meson.build
> > index e37d4fe2b..d17ca76eb 100644
> > --- a/drivers/meson.build
> > +++ b/drivers/meson.build
> > @@ -46,7 +46,7 @@ foreach class:driver_classes
> >  		# set up internal deps. Drivers can
> > append/override as necessary
> >  		deps = std_deps
> >  		# ext_deps: Stores external library dependency got
> > -		# using dependency() or cc.find_library(). For
> > most cases, we
> > +		# using dependency() (preferred) or
> > find_library(). For most cases, we
> >  		# probably also need to specify the "-l" flags in
> >  		# pkgconfig_extra_libs variable too, so that it
> > can be reflected
> >  		# in the pkgconfig output for static builds
> 
> The last part of this comment can now be deleted, right? If we use
> dependency() we don't need to use pkgconfig_extra_libs.
> 
> Is the pkgconfig_extra_libs variable still needed after these
> changes?
> 
> /Bruce

Yes, as we can't use dependency() for everything unfortunately - only
for those projects that ship a pkg-config file, a cmake file or that
Meson has built-in knowledge of (like llvm or libpcap).
I'll update that comment accordingly in v4.

-- 
Kind regards,
Luca Boccassi