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

[Luca Boccassi <bluca@debian.org>]

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
take extra time, and avoid adding the linker flag manually which causes
it to be duplicated.

An internal checker has been added to Meson 0.42 to detect libpcap,
which ships a custom tool rather than a pkg-config file, so bump the
minimum Meson version from 0.41 to 0.42.

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.

Fixes: a25a650be5f0 ("build: add infrastructure for meson and ninja builds")
Cc: stable@dpdk.org

Signed-off-by: Luca Boccassi <bluca@debian.org>
---

Bruce, dependency() by default tries pkg-config first, then cmake, then
the internal project-specific finders (like pcap). If you think it's
worth it I can add fallbacks in case a system, for whatever reason,
does not install a pc file despite the upstream project providing one.
It would add more clutter and more verbosity, but it would not cause
other issues.

 app/meson.build                    |  2 +-
 config/meson.build                 | 10 +++++-----
 drivers/crypto/ccp/meson.build     |  1 -
 drivers/crypto/openssl/meson.build |  1 -
 drivers/crypto/qat/meson.build     |  1 -
 drivers/meson.build                |  4 ++--
 drivers/net/bnx2x/meson.build      |  2 +-
 drivers/net/mlx4/meson.build       |  6 +++---
 drivers/net/mlx5/meson.build       |  6 +++---
 drivers/net/pcap/meson.build       |  5 ++---
 examples/meson.build               |  2 +-
 lib/librte_bpf/meson.build         |  4 ++--
 lib/librte_telemetry/meson.build   |  2 +-
 lib/meson.build                    |  2 +-
 meson.build                        |  2 +-
 test/test/meson.build              |  1 +
 16 files changed, 24 insertions(+), 27 deletions(-)

diff --git a/app/meson.build b/app/meson.build
index 47a2a8615..e31386f1a 100644
--- a/app/meson.build
+++ b/app/meson.build
@@ -29,7 +29,7 @@ foreach app:apps
 
 	# use "deps" for internal DPDK dependencies, and "ext_deps" for
 	# external package/library requirements
-	ext_deps = []
+	ext_deps = [libbsd]
 	deps = dpdk_app_link_libraries
 
 	subdir(name)
diff --git a/config/meson.build b/config/meson.build
index db32499b3..e1af468ee 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -74,11 +74,11 @@ if numa_dep.found() and cc.has_header('numaif.h')
 endif
 
 # check for strlcpy
-if host_machine.system() == 'linux' and cc.find_library('bsd',
-		required: false).found() and cc.has_header('bsd/string.h')
-	dpdk_conf.set('RTE_USE_LIBBSD', 1)
-	add_project_link_arguments('-lbsd', language: 'c')
-	dpdk_extra_ldflags += '-lbsd'
+if host_machine.system() == 'linux'
+	libbsd = dependency('libbsd', required: false)
+	if libbsd.found()
+		dpdk_conf.set('RTE_USE_LIBBSD', 1)
+	endif
 endif
 
 # add -include rte_config to cflags
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 c3c66bbc0..f442f9719 100644
--- a/drivers/meson.build
+++ b/drivers/meson.build
@@ -46,11 +46,11 @@ 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(). 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
-		ext_deps = []
+		ext_deps = [libbsd]
 		pkgconfig_extra_libs = []
 
 		# pull in driver directory which should assign to each of the above
diff --git a/drivers/net/bnx2x/meson.build b/drivers/net/bnx2x/meson.build
index e3c688869..dd189ffc4 100644
--- a/drivers/net/bnx2x/meson.build
+++ b/drivers/net/bnx2x/meson.build
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright(c) 2018 Intel Corporation
 
-dep = cc.find_library('z', required: false)
+dep = dependency('zlib', required: false)
 build = dep.found()
 ext_deps += dep
 cflags += '-DZLIB_CONST'
diff --git a/drivers/net/mlx4/meson.build b/drivers/net/mlx4/meson.build
index 7de571e2a..4ba4e93b6 100644
--- a/drivers/net/mlx4/meson.build
+++ b/drivers/net/mlx4/meson.build
@@ -14,9 +14,9 @@ if pmd_dlopen
 	]
 endif
 libs = [
-	cc.find_library('mnl', required:false),
-	cc.find_library('mlx4', required:false),
-	cc.find_library('ibverbs', required:false),
+	dependency('libmnl', required:false),
+	dependency('libmlx4', required:false),
+	dependency('libibverbs', required:false),
 ]
 build = true
 foreach lib:libs
diff --git a/drivers/net/mlx5/meson.build b/drivers/net/mlx5/meson.build
index 28938db0f..7ff3660fa 100644
--- a/drivers/net/mlx5/meson.build
+++ b/drivers/net/mlx5/meson.build
@@ -14,9 +14,9 @@ if pmd_dlopen
 	]
 endif
 libs = [
-	cc.find_library('mnl', required:false),
-	cc.find_library('mlx5', required:false),
-	cc.find_library('ibverbs', required:false),
+	dependency('libmnl', required:false),
+	dependency('libmlx5', required:false),
+	dependency('libibverbs', required:false),
 ]
 build = true
 foreach lib:libs
diff --git a/drivers/net/pcap/meson.build b/drivers/net/pcap/meson.build
index 0c4e0201a..89c9d7a74 100644
--- a/drivers/net/pcap/meson.build
+++ b/drivers/net/pcap/meson.build
@@ -1,12 +1,11 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright(c) 2017 Intel Corporation
 
-pcap_dep = cc.find_library('pcap', required: false)
-if pcap_dep.found() and cc.has_header('pcap.h', dependencies: pcap_dep)
+pcap_dep = dependency('pcap', required: false)
+if pcap_dep.found()
 	build = true
 else
 	build = false
 endif
 sources = files('rte_eth_pcap.c')
 ext_deps += pcap_dep
-pkgconfig_extra_libs += '-lpcap'
diff --git a/examples/meson.build b/examples/meson.build
index af81c762e..881e2da33 100644
--- a/examples/meson.build
+++ b/examples/meson.build
@@ -33,7 +33,7 @@ foreach example: examples
 	allow_experimental_apis = false
 	cflags = default_cflags
 
-	ext_deps = [execinfo]
+	ext_deps = [execinfo libbsd]
 	includes = [include_directories(example)]
 	deps = ['eal', 'mempool', 'net', 'mbuf', 'ethdev', 'cmdline']
 	subdir(example)
diff --git a/lib/librte_bpf/meson.build b/lib/librte_bpf/meson.build
index bc0cd78f9..c3b1f698e 100644
--- a/lib/librte_bpf/meson.build
+++ b/lib/librte_bpf/meson.build
@@ -18,8 +18,8 @@ install_headers = files('bpf_def.h',
 
 deps += ['mbuf', 'net', 'ethdev']
 
-dep = cc.find_library('elf', required: false)
-if dep.found() == true and cc.has_header('libelf.h', dependencies: dep)
+dep = dependency('libelf', required: false)
+if dep.found()
 	sources += files('bpf_load_elf.c')
 	ext_deps += dep
 endif
diff --git a/lib/librte_telemetry/meson.build b/lib/librte_telemetry/meson.build
index 9492f544e..cafb26f08 100644
--- a/lib/librte_telemetry/meson.build
+++ b/lib/librte_telemetry/meson.build
@@ -6,7 +6,7 @@ headers = files('rte_telemetry.h', 'rte_telemetry_internal.h', 'rte_telemetry_pa
 deps += ['metrics', 'ethdev']
 cflags += '-DALLOW_EXPERIMENTAL_API'
 
-jansson = cc.find_library('jansson', required: false)
+jansson = dependency('jansson', required: false)
 if jansson.found()
 	ext_deps += jansson
 	dpdk_app_link_libraries += ['telemetry']
diff --git a/lib/meson.build b/lib/meson.build
index a2dd52e17..b2a18f488 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -51,7 +51,7 @@ foreach l:libraries
 
 	# use "deps" for internal DPDK dependencies, and "ext_deps" for
 	# external package/library requirements
-	ext_deps = []
+	ext_deps = [libbsd]
 	deps = []
 	# eal is standard dependency once built
 	if dpdk_conf.has('RTE_LIBRTE_EAL')
diff --git a/meson.build b/meson.build
index 617e88589..f87dc235f 100644
--- a/meson.build
+++ b/meson.build
@@ -5,7 +5,7 @@ project('DPDK', 'C',
 	version: '19.02.0-rc1',
 	license: 'BSD',
 	default_options: ['buildtype=release', 'default_library=static'],
-	meson_version: '>= 0.41'
+	meson_version: '>= 0.42'
 )
 
 # set up some global vars for compiler, platform, configuration, etc.
diff --git a/test/test/meson.build b/test/test/meson.build
index 5a4816fed..886c29fb4 100644
--- a/test/test/meson.build
+++ b/test/test/meson.build
@@ -279,6 +279,7 @@ foreach d:test_deps
 	test_dep_objs += get_variable(def_lib + '_rte_' + d)
 endforeach
 test_dep_objs += cc.find_library('execinfo', required: false)
+test_dep_objs += libbsd
 
 link_libs = []
 if get_option('default_library') == 'static'
-- 
2.19.2