build: enable BSD features visibility for FreeBSD

When a component uses either XOPEN_SOURCE or POSIX_C_SOURCE macro
explicitly in its build recipe, it restricts visibility of a non POSIX
features subset, such as IANA protocol numbers (IPPROTO_* macros).
Non standard features are enabled by default for DPDK both for Linux
thanks to _GNU_SOURCE and for FreeBSD thanks to __BSD_VISIBLE. However
using XOPEN_SOURCE or POSIX_(C_)SOURCE in a component causes
__BSD_VISIBLE to be defined to 0 for FreeBSD, causing different feature
sets visibility for Linux and FreeBSD. It restricts from using IPPROTO
macros in public headers, such as rte_ip.h, despite the fact they are
already widely used in sources.

Add __BSD_VISIBLE macro specified unconditionally for FreeBSD targets
which enforces feature sets visibility unification between Linux and
FreeBSD.

Add single -D_GNU_SOURCE to config/meson.build as a project argument
instead of adding separate directive for each project subtree.

This patch solves the problem of build breaks for [1] on FreeBSD [2]
following the discussion [3].

[1] https://mails.dpdk.org/archives/dev/2019-May/131885.html
[2] http://mails.dpdk.org/archives/test-report/2019-May/082263.html
[3] https://mails.dpdk.org/archives/dev/2019-May/132110.html

Signed-off-by: Marcin Smoczynski <marcinx.smoczynski@intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>

app/meson.build

@@ -22,9 +22,6 @@ lib_execinfo = cc.find_library('execinfo', required: false)
 
 default_cflags = machine_args
 
-# specify -D_GNU_SOURCE unconditionally
-default_cflags += '-D_GNU_SOURCE'
-
 foreach app:apps
 	build = true
 	name = app

config/meson.build

@@ -188,3 +188,11 @@ install_headers('rte_config.h', subdir: get_option('include_subdir_arch'))
 
 # enable VFIO only if it is linux OS
 dpdk_conf.set('RTE_EAL_VFIO', is_linux)
+
+# specify -D_GNU_SOURCE unconditionally
+add_project_arguments('-D_GNU_SOURCE', language: 'c')
+
+# specify -D__BSD_VISIBLE for FreeBSD
+if is_freebsd
+	add_project_arguments('-D__BSD_VISIBLE', language: 'c')
+endif

drivers/meson.build

@@ -21,9 +21,6 @@ if cc.has_argument('-Wno-format-truncation')
 	default_cflags += '-Wno-format-truncation'
 endif
 
-# specify -D_GNU_SOURCE unconditionally
-default_cflags += '-D_GNU_SOURCE'
-
 foreach class:dpdk_driver_classes
 	drivers = []
 	std_deps = []

examples/meson.build

@@ -65,9 +65,6 @@ if cc.has_argument('-Wno-format-truncation')
 	default_cflags += '-Wno-format-truncation'
 endif
 
-# specify -D_GNU_SOURCE unconditionally
-default_cflags += '-D_GNU_SOURCE'
-
 foreach example: examples
 	name = example.split('/')[-1]
 	build = true

lib/meson.build

@@ -41,9 +41,6 @@ endif
 
 enabled_libs = [] # used to print summary at the end
 
-# -D_GNU_SOURCE unconditionally
-default_cflags += '-D_GNU_SOURCE'
-
 foreach l:libraries
 	build = true
 	name = l

meson.build

@@ -63,6 +63,10 @@ configure_file(output: build_cfg,
 dpdk_drivers = ['-Wl,--whole-archive'] + dpdk_drivers + ['-Wl,--no-whole-archive']
 
 pkg = import('pkgconfig')
+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(),
 	version: meson.project_version(),
@@ -75,7 +79,7 @@ pkg.generate(name: meson.project_name(),
 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: ['-include', 'rte_config.h'] + machine_args
+	extra_cflags: pkg_extra_cflags
 )
 
 # final output, list all the libs and drivers to be built

mk/target/generic/rte.vars.mk

@@ -111,6 +111,11 @@ endif
 # always define _GNU_SOURCE
 CFLAGS += -D_GNU_SOURCE
 
+# define __BSD_VISIBLE when building for FreeBSD
+ifeq ($(CONFIG_RTE_EXEC_ENV_FREEBSD),y)
+CFLAGS += -D__BSD_VISIBLE
+endif
+
 export CFLAGS
 export LDFLAGS