build: support building ABI versioned files twice

Any file with ABI versioned functions needs different macros for shared and
static builds, so we need to accommodate that. Rather than building
everything twice, we just flag to the build system which libraries need
that handling, by setting use_function_versioning in the meson.build files.

To ensure we don't get silent errors at build time due to this meson flag
being missed, we add an explicit error to the function versioning header
file if a known C macro is not defined. Since "make" builds always only
build one of shared or static libraries, this define can be always set, and
so is added to the global CFLAGS. For meson, the build flag - and therefore
the C define - is set for the three libraries that need the function
versioning: "distributor", "lpm" and "timer".

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Tested-by: Andrzej Ostruszka <amo@semihalf.com>
Reviewed-by: Andrzej Ostruszka <amo@semihalf.com>

config/rte_config.h

@@ -31,9 +31,6 @@
 
 /****** library defines ********/
 
-/* compat defines */
-#define RTE_BUILD_SHARED_LIB
-
 /* EAL defines */
 #define RTE_MAX_HEAPS 32
 #define RTE_MAX_MEMSEG_LISTS 128

doc/guides/contributing/coding_style.rst

@@ -948,6 +948,13 @@ reason
 	built. For missing dependencies this should be of the form
 	``'missing dependency, "libname"'``.
 
+use_function_versioning
+	**Default Value = false**.
+	Specifies if the library in question has ABI versioned functions. If it
+	has, this value should be set to ensure that the C files are compiled
+	twice with suitable parameters for each of shared or static library
+	builds.
+
 version
 	**Default Value = 1**.
 	Specifies the ABI version of the library, and is used as the major

lib/librte_distributor/meson.build

@@ -9,6 +9,7 @@ else
 endif
 headers = files('rte_distributor.h')
 deps += ['mbuf']
+use_function_versioning = true
 
 # for clang 32-bit compiles we need libatomic for 64-bit atomic ops
 if cc.get_id() == 'clang' and dpdk_conf.get('RTE_ARCH_64') == false

lib/librte_eal/common/include/rte_function_versioning.h

@@ -7,6 +7,10 @@
 #define _RTE_FUNCTION_VERSIONING_H_
 #include <rte_common.h>
 
+#ifndef RTE_USE_FUNCTION_VERSIONING
+#error Use of function versioning disabled, is "use_function_versioning=true" in meson.build?
+#endif
+
 #ifdef RTE_BUILD_SHARED_LIB
 
 /*

lib/librte_lpm/meson.build

@@ -8,3 +8,4 @@ headers = files('rte_lpm.h', 'rte_lpm6.h')
 # without worrying about which architecture we actually need
 headers += files('rte_lpm_altivec.h', 'rte_lpm_neon.h', 'rte_lpm_sse.h')
 deps += ['hash']
+use_function_versioning = true

lib/librte_timer/meson.build

@@ -4,3 +4,4 @@
 sources = files('rte_timer.c')
 headers = files('rte_timer.h')
 allow_experimental_apis = true
+use_function_versioning = true

lib/meson.build

@@ -47,6 +47,7 @@ foreach l:libraries
 	name = l
 	version = 1
 	allow_experimental_apis = false
+	use_function_versioning = false
 	sources = []
 	headers = []
 	includes = []
@@ -99,6 +100,9 @@ foreach l:libraries
 			if allow_experimental_apis
 				cflags += '-DALLOW_EXPERIMENTAL_API'
 			endif
+			if use_function_versioning
+				cflags += '-DRTE_USE_FUNCTION_VERSIONING'
+			endif
 
 			if get_option('per_library_versions')
 				lib_version = '@0@.1'.format(version)
@@ -120,9 +124,15 @@ foreach l:libraries
 					include_directories: includes,
 					dependencies: static_deps)
 
-			# then use pre-build objects to build shared lib
-			sources = []
-			objs += static_lib.extract_all_objects(recursive: false)
+			if not use_function_versioning
+				# use pre-build objects to build shared lib
+				sources = []
+				objs += static_lib.extract_all_objects(recursive: false)
+			else
+				# for compat we need to rebuild with
+				# RTE_BUILD_SHARED_LIB defined
+				cflags += '-DRTE_BUILD_SHARED_LIB'
+			endif
 			version_map = '@0@/@1@/rte_@2@_version.map'.format(
 					meson.current_source_dir(), dir_name, name)
 			implib = dir_name + '.dll.a'

mk/target/generic/rte.vars.mk

@@ -90,6 +90,14 @@ ASFLAGS += $(TARGET_ASFLAGS)
 CFLAGS += -I$(RTE_OUTPUT)/include
 LDFLAGS += -L$(RTE_OUTPUT)/lib
 
+# add in flag for supporting function versioning. The define is used in meson
+# builds to ensure that the user has properly flagged the unit in question as
+# using function versioning so it can be built twice - once for static lib and
+# then a second time for the shared lib. Since make only builds one library
+# type at a time, such precautions aren't necessary, so we can globally define
+# the flag
+CFLAGS += -DRTE_USE_FUNCTION_VERSIONING
+
 # always include rte_config.h: the one in $(RTE_OUTPUT)/include is
 # the configuration of SDK when $(BUILDING_RTE_SDK) is true, or the
 # configuration of the application if $(BUILDING_RTE_SDK) is not