libsinsp: Refine pkg-config file generation.

The generated pkg-config file now makes use of pkg-config Requires and
Requires.static fields, which should reduce over-linking when linking
to shared libraries.

* userspace/libsinsp/libsinsp.pc.in: Delete file.
* userspace/libsinsp/CMakeLists.txt: Separate libraries into
pkg-config Requires and Requires.private lists.  Generate the
libsinsp.pc file via 'file', which supports generator expressions.

Signed-off-by: Maxim Cournoyer <maxim.cournoyer@gmail.com>

userspace/libscap/libscap.pc.in

@@ -1,10 +1,11 @@
-prefix=${pcfiledir}/../..
+prefix=@CMAKE_INSTALL_PREFIX@
 libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
 includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
 
 Name: libscap
 Description: lib for System CAPture
 Version: @FALCOSECURITY_LIBS_VERSION@
 
-Libs: -L${libdir} @LIBSCAP_LINK_LIBDIRS_FLAGS@ @LIBSCAP_LINK_LIBRARIES_FLAGS@
+Requires: zlib
+Libs: -L${libdir} -L{libdir}/@LIBS_PACKAGE_NAME@/libscap @LIBSCAP_LINK_LIBDIRS_FLAGS@ @LIBSCAP_LINK_LIBRARIES_FLAGS@
 Cflags: -I${includedir}/@LIBS_PACKAGE_NAME@/libscap -I${includedir}/@LIBS_PACKAGE_NAME@ -I${includedir}/@LIBS_PACKAGE_NAME@/driver

userspace/libsinsp/CMakeLists.txt

@@ -169,12 +169,14 @@ target_link_libraries(sinsp
 			"${RE2_LIB}"
 )
 
-set(SINSP_PKGCONFIG_LIBRARIES
-	scap
-	"${ZLIB_LIB}"
-	"${CURL_LIBRARIES}"
-	"${JSONCPP_LIB}"
-	"${RE2_LIB}"
+set(SINSP_PKGCONFIG_LIBRARIES)
+set(SINSP_PKGCONFIG_REQUIRES
+	$<$<BOOL:${JSONCPP_LIB}>:jsoncpp>
+)
+
+set(SINSP_PKGCONFIG_REQUIRES_PRIVATE
+	$<$<BOOL:${CURL_LIBRARIES}>:libcurl>
+	$<$<BOOL:${RE2_LIB}>:re2>
 )
 
 if(NOT EMSCRIPTEN)
@@ -184,7 +186,12 @@ if(NOT EMSCRIPTEN)
 		PRIVATE
 		"${TBB_LIB}"
 	)
-	list(APPEND SINSP_PKGCONFIG_LIBRARIES "${CARES_LIB}")
+	list(APPEND SINSP_PKGCONFIG_REQUIRES
+		$<$<BOOL:${CARES_LIB}>:libcares>
+	)
+	list(APPEND SINSP_PKGCONFIG_REQUIRES_PRIVATE
+		$<$<BOOL:${TBB_LIB}>:tbb>
+	)
 endif()
 
 if(USE_BUNDLED_VALIJSON)
@@ -248,13 +255,12 @@ if(NOT WIN32)
 						"${PROTOBUF_LIB}"
 						"${CARES_LIB}"
 			)
-			list(APPEND SINSP_PKGCONFIG_LIBRARIES
-						"${GRPC_LIBRARIES}"
-						"${GRPCPP_LIB}"
-						"${GRPC_LIB}"
-						"${GPR_LIB}"
-						"${PROTOBUF_LIB}"
-						"${CARES_LIB}"
+			list(APPEND SINSP_PKGCONFIG_REQUIRES
+				$<$<BOOL:${GPR_LIB}>:gpr>
+				$<$<BOOL:${GRPC_LIB}>:grpc>
+				$<$<BOOL:${GRPCPP_LIB}>:grpc++>
+				$<$<BOOL:${PROTOBUF_LIB}>:protobuf>
+				$<$<BOOL:${CARES_LIB}>:libcares>
 			)
 
 			if(NOT MUSL_OPTIMIZED_BUILD)
@@ -269,7 +275,8 @@ if(NOT WIN32)
 	endif() # NOT APPLE
 
 	target_link_libraries(sinsp INTERFACE "${OPENSSL_LIBRARIES}")
-	list(APPEND SINSP_PKGCONFIG_LIBRARIES "${OPENSSL_LIBRARIES}")
+	list(APPEND SINSP_PKGCONFIG_REQUIRES
+		$<$<BOOL:${OPENSSL_LIBRARIES}>:libcrypto libssl>)
 
 	target_link_libraries(sinsp INTERFACE dl pthread)
 	list(APPEND SINSP_PKGCONFIG_LIBRARIES dl pthread)
@@ -306,41 +313,25 @@ if(NOT DEFINED SINSP_AGENT_CGROUP_MEM_PATH_ENV_VAR)
 endif()
 add_definitions(-DSINSP_AGENT_CGROUP_MEM_PATH_ENV_VAR="${SINSP_AGENT_CGROUP_MEM_PATH_ENV_VAR}")
 
-# Build our pkg-config "Libs:" flags. For now, loop over SINSP_PKGCONFIG_LIBRARIES. If
-# we ever start using pkg_search_module or pkg_check_modules in cmake/modules
-# we could add each module to our "Requires:" line instead. We might need to
-# expand this to use some of the techniques in
-# https://github.com/curl/curl/blob/curl-7_84_0/CMakeLists.txt#L1539
 set(SINSP_PKG_CONFIG_LIBS)
 set(SINSP_PKG_CONFIG_LIBDIRS "")
-foreach(sinsp_lib ${SINSP_PKGCONFIG_LIBRARIES})
-	if(${sinsp_lib} MATCHES "^-")
-		# We have a flag. Pass it through unchanged.
-		list(APPEND SINSP_PKG_CONFIG_LIBS ${sinsp_lib})
-	elseif(${sinsp_lib} MATCHES "/")
-		# We have a path. Convert it to -L<dir> + -l<lib>.
-		get_filename_component(sinsp_lib_dir ${sinsp_lib} DIRECTORY)
-		list(APPEND SINSP_PKG_CONFIG_LIBDIRS -L${sinsp_lib_dir})
-		get_filename_component(sinsp_lib_base ${sinsp_lib} NAME_WE)
-		string(REGEX REPLACE "^lib" "" sinsp_lib_base ${sinsp_lib_base})
-		list(APPEND SINSP_PKG_CONFIG_LIBS -l${sinsp_lib_base})
-	elseif(${sinsp_lib} STREQUAL "scap")
-		# We require libscap.pc, so skip it.
-	else()
-		# Assume we have a plain library name. Prefix it with "-l".
-		list(APPEND SINSP_PKG_CONFIG_LIBS -l${sinsp_lib})
-	endif()
-endforeach()
-
-# Build our pkg-config "Cflags:" flags.
-set(SINSP_PKG_CONFIG_INCLUDES "")
-foreach(sinsp_include_directory ${LIBSINSP_INCLUDE_DIRS})
-	list(APPEND SINSP_PKG_CONFIG_INCLUDES -I${sinsp_include_directory})
-endforeach()
-
-string(REPLACE ";" " " SINSP_PKG_CONFIG_LIBS "${SINSP_PKG_CONFIG_LIBS}")
-list(REMOVE_DUPLICATES SINSP_PKG_CONFIG_LIBDIRS)
-string(REPLACE ";" " " SINSP_PKG_CONFIG_LIBDIRS "${SINSP_PKG_CONFIG_LIBDIRS}")
-list(REMOVE_DUPLICATES SINSP_PKG_CONFIG_INCLUDES)
-string(REPLACE ";" " " SINSP_PKG_CONFIG_INCLUDES "${SINSP_PKG_CONFIG_INCLUDES}")
-configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libsinsp.pc.in ${CMAKE_CURRENT_BINARY_DIR}/libsinsp.pc @ONLY)
+
+list(REMOVE_DUPLICATES SINSP_PKGCONFIG_LIBRARIES)
+list(REMOVE_DUPLICATES SINSP_PKGCONFIG_REQUIRES)
+list(REMOVE_DUPLICATES SINSP_PKGCONFIG_REQUIRES_PRIVATE)
+
+file(GENERATE
+	OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/libsinsp.pc
+	CONTENT "prefix=${CMAKE_INSTALL_PREFIX}
+libdir=\${prefix}/${CMAKE_INSTALL_LIBDIR}
+includedir=\${prefix}/${CMAKE_INSTALL_INCLUDEDIR}
+
+Name: libsinsp
+Description: lib for System INSPection
+Version: ${FALCOSECURITY_LIBS_VERSION}
+
+Requires: libscap $<JOIN:${SINSP_PKGCONFIG_REQUIRES}, >
+Requires.private: $<JOIN:${SINSP_PKGCONFIG_REQUIRES_PRIVATE}, >
+Libs: -L\${libdir} -lsinsp $<JOIN:${SINSP_PKG_CONFIG_LIBS}, -l>
+Cflags: -I\${includedir}/${LIBS_PACKAGE_NAME}/libsinsp -I\${includedir}/${LIBS_PACKAGE_NAME}/driver -I\${includedir}/${LIBS_PACKAGE_NAME}
+")