[dpdk-dev] [PATCH v2 5/7] build/pkg-config: output driver libs first for static build

[Bruce Richardson]

When calling pkg-config --static --libs, pkg-config will always output the
regular libs first, and then the extra libs from libraries.private field,
since the assumption is that those are additional dependencies for building
statically that the .a files depend upon.

However, for DPDK, we only link the driver files for static builds, and
those need to come *before* the regular libraries. To get this result, we
need two pkgconfig files for DPDK, one for the shared libs, and a second
for the static libs and drivers, which depends upon the first. Using a
dependency means that the shared libs are printed only after the
libraries.private field rather than before.

Without this patch, the linking works in DPDK because in all cases we
specify the libraries after the drivers in the Libs.private line, ensuring
that the references to the libs from the drivers can be resolved. The
current output is therefore of the form, "(shared)libs, drivers,
(static)libs", while after this patch the output is, "drivers,
(static)libs, (shared)libs". The former case will not work if we use the
--whole-archive flag on the static libs as it will lead to duplicate
definitions due to some references having been previously resolved from the
shared libraries. By ensuring the shared libraries come last in the link
link, this issue does not occur, as duplicate references when linking the
shared libs will be ignored.

Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
---
V2: expanded commit log message with extra info, and updated pkg-config
file description to make it clearer that one file is internal-only
---
 buildtools/pkg-config/meson.build | 33 +++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/buildtools/pkg-config/meson.build b/buildtools/pkg-config/meson.build
index 85d59972d..aabd00eed 100644
--- a/buildtools/pkg-config/meson.build
+++ b/buildtools/pkg-config/meson.build
@@ -10,17 +10,34 @@ pkg_extra_cflags = ['-include', 'rte_config.h'] + machine_args
 if is_freebsd
 	pkg_extra_cflags += ['-D__BSD_VISIBLE']
 endif
-pkg.generate(name: meson.project_name(),
-	filebase: 'lib' + meson.project_name().to_lower(),
+
+# When calling pkg-config --static --libs, pkg-config will always output the
+# regular libs first, and then the extra libs from libraries.private field,
+# since the assumption is that those are additional dependencies for building
+# statically that the .a files depend upon. However, for DPDK, we only link
+# the driver files for static builds, and those need to come *before* the
+# regular libraries. To get this result, we need two pkgconfig files for DPDK,
+# one for the shared libs, and a second for the static libs and drivers, which
+# depends upon the first. Using a dependency means that the shared libs are
+# printed only after the libraries.private field rather than before.
+pkg.generate(name: 'dpdk-libs',
+	filebase: 'libdpdk-libs',
+	description: '''Internal-only DPDK pkgconfig file. Not for direct use.
+Use libdpdk.pc instead of this file to query DPDK compile/link arguments''',
 	version: meson.project_version(),
+	subdirs: [get_option('include_subdir_arch'), '.'],
+	extra_cflags: pkg_extra_cflags,
 	libraries: dpdk_libraries,
-	libraries_private: dpdk_drivers + dpdk_static_libraries +
-			['-Wl,-Bdynamic'] + dpdk_extra_ldflags,
-	requires: libbsd, # apps using rte_string_fns.h may need this if enabled
-	                  # if libbsd is not enabled, then this is blank
+	libraries_private: dpdk_extra_ldflags)
+
+pkg.generate(name: 'DPDK', # main DPDK pkgconfig file
+	filebase: 'libdpdk',
+	version: meson.project_version(),
 	description: '''The Data Plane Development Kit (DPDK).
 Note that CFLAGS might contain an -march flag higher than typical baseline.
 This is required for a number of static inline functions in the public headers.''',
-	subdirs: [get_option('include_subdir_arch'), '.'],
-	extra_cflags: pkg_extra_cflags
+	requires: ['libdpdk-libs', libbsd], # may need libbsd for string funcs
+	                  # if libbsd is not enabled, then this is blank
+	libraries_private: dpdk_drivers + dpdk_static_libraries +
+			['-Wl,-Bdynamic']
 )
-- 
2.20.1