[PATCH 5/5] build: select optional libraries

[David Marchand <david.marchand@redhat.com>]

There is currently no way to know which libraries are optional.
Introduce a enable_libs option (close to what we have for drivers) so
that packagers or projects consuming DPDK can more easily select the
optional libraries that matter to them and disable other optional
libraries.

Note: the enabled_libs variable is renamed for sake of consistency.

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
 buildtools/chkincs/meson.build |  2 +-
 lib/meson.build                | 34 ++++++++++++++++++----------------
 meson.build                    |  3 ++-
 meson_options.txt              |  2 ++
 4 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/buildtools/chkincs/meson.build b/buildtools/chkincs/meson.build
index 5ffca89761..6b93d5f46c 100644
--- a/buildtools/chkincs/meson.build
+++ b/buildtools/chkincs/meson.build
@@ -18,7 +18,7 @@ sources = files('main.c')
 sources += gen_c_files.process(dpdk_chkinc_headers)
 
 deps = []
-foreach l:enabled_libs
+foreach l:dpdk_libs_enabled
     deps += get_variable('static_rte_' + l)
 endforeach
 
diff --git a/lib/meson.build b/lib/meson.build
index dad9fce14d..47c857c0fc 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -78,17 +78,10 @@ optional_libs = [
         'vhost',
 ]
 
-disabled_libs = []
-opt_disabled_libs = run_command(list_dir_globs, get_option('disable_libs'),
+enable_libs = run_command(list_dir_globs, get_option('enable_libs'),
+        check: true).stdout().split()
+disable_libs = run_command(list_dir_globs, get_option('disable_libs'),
         check: true).stdout().split()
-foreach l:opt_disabled_libs
-    if not optional_libs.contains(l)
-        warning('Cannot disable mandatory library "@0@"'.format(l))
-        continue
-    endif
-    disabled_libs += l
-endforeach
-
 
 default_cflags = machine_args
 default_cflags += ['-DALLOW_EXPERIMENTAL_API']
@@ -98,8 +91,6 @@ if cc.has_argument('-Wno-format-truncation')
     default_cflags += '-Wno-format-truncation'
 endif
 
-enabled_libs = [] # used to print summary at the end
-
 foreach l:libraries
     build = true
     reason = '<unknown reason>' # set if build == false to explain why
@@ -123,10 +114,21 @@ foreach l:libraries
         deps += ['eal']
     endif
 
-    if disabled_libs.contains(l)
-        build = false
-        reason = 'explicitly disabled via build config'
+    if optional_libs.contains(l)
+        # check for enabled libraries only if one is set in config
+        if enable_libs.length() != 0 and not enable_libs.contains(l)
+            build = false
+            reason = 'not in enabled libraries build config'
+        elif disable_libs.contains(l)
+            build = false
+            reason = 'explicitly disabled via build config'
+        endif
     else
+        if disable_libs.contains(l)
+            warning('Cannot disable mandatory library "@0@"'.format(l))
+        endif
+    endif
+    if build
         subdir(l)
     endif
     if name != l
@@ -150,7 +152,7 @@ foreach l:libraries
         static_deps += [get_variable('static_rte_' + d)]
     endforeach
 
-    enabled_libs += name
+    dpdk_libs_enabled += name
     dpdk_conf.set('RTE_LIB_' + name.to_upper(), 1)
     install_headers(headers)
     install_headers(indirect_headers)
diff --git a/meson.build b/meson.build
index 12cb6e0e83..65855ceee8 100644
--- a/meson.build
+++ b/meson.build
@@ -35,6 +35,7 @@ dpdk_driver_classes = []
 dpdk_drivers = []
 dpdk_extra_ldflags = []
 dpdk_libs_disabled = []
+dpdk_libs_enabled = []
 dpdk_drvs_disabled = []
 abi_version_file = files('ABI_VERSION')
 
@@ -102,7 +103,7 @@ subdir('buildtools/pkg-config')
 output_message = '\n=================\nLibraries Enabled\n=================\n'
 output_message += '\nlibs:\n\t'
 output_count = 0
-foreach lib:enabled_libs
+foreach lib:dpdk_libs_enabled
     output_message += lib + ', '
     output_count += 1
     if output_count == 8
diff --git a/meson_options.txt b/meson_options.txt
index 7c220ad68d..ccb92cff7a 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -16,6 +16,8 @@ option('enable_docs', type: 'boolean', value: false, description:
        'build documentation')
 option('enable_drivers', type: 'string', value: '', description:
        'Comma-separated list of drivers to build. If unspecified, build all drivers.')
+option('enable_libs', type: 'string', value: '', description:
+       'Comma-separated list of libraries to explicitly enable.')
 option('enable_driver_sdk', type: 'boolean', value: false, description:
        'Install headers to build drivers.')
 option('enable_kmods', type: 'boolean', value: false, description:
-- 
2.23.0