build: use the system provided c-ares if found

e.g. buildroot has logic to build c-ares,
so if pkg_check_modules can find a suitable version,
then use that one if -DFLB_PREFER_SYSTEM_LIB_CARES=Yes.

Note that the CheckIncludeFiles include for wasm is added,
since that was done by c-ares otherwise.

Signed-off-by: Thomas Devoogdt <[email protected]>

Author: ThomasDevoogdt

CMakeLists.txt

@@ -204,6 +204,7 @@ option(FLB_RUN_LDCONFIG "Enable execution of ldconfig after installation" No)
 # Prefer system libraries if available
 option(FLB_PREFER_SYSTEM_LIBS             "Prefer system libraries"                   No)
 option(FLB_PREFER_SYSTEM_LIB_BACKTRACE    "Prefer the libbacktrace system library"    ${FLB_PREFER_SYSTEM_LIBS})
+option(FLB_PREFER_SYSTEM_LIB_CARES        "Prefer the libcares system library"        ${FLB_PREFER_SYSTEM_LIBS})
 option(FLB_PREFER_SYSTEM_LIB_JEMALLOC     "Prefer the libjemalloc system library"     ${FLB_PREFER_SYSTEM_LIBS})
 option(FLB_PREFER_SYSTEM_LIB_LUAJIT       "Prefer the libluajit system library"       ${FLB_PREFER_SYSTEM_LIBS})
 option(FLB_PREFER_SYSTEM_LIB_NGHTTP2      "Prefer the libnghttp2 system library"      ${FLB_PREFER_SYSTEM_LIBS})
@@ -504,16 +505,16 @@ else()
 endif()
 
 # C-Ares (DNS library)
-FLB_OPTION(CARES_STATIC      ON)
-FLB_OPTION(CARES_SHARED      OFF)
-FLB_OPTION(CARES_INSTALL     OFF)
-FLB_OPTION(CARES_BUILD_TESTS OFF)
-FLB_OPTION(CARES_BUILD_TOOLS OFF)
-if (FLB_SYSTEM_MACOS)
-  # macOS SDK always has <arpa/nameser.h>.
-  FLB_DEFINITION(CARES_HAVE_ARPA_NAMESER_H)
+if(FLB_PREFER_SYSTEM_LIB_CARES)
+  find_package(PkgConfig)
+  pkg_check_modules(LIBCARES libcares>=1.18.0)
+endif()
+if(LIBCARES_FOUND)
+  include_directories(${LIBCARES_INCLUDE_DIRS})
+  link_directories(${LIBCARES_LIBRARY_DIRS})
+else()
+  include(cmake/cares.cmake)
 endif()
-add_subdirectory(${FLB_PATH_LIB_CARES})# EXCLUDE_FROM_ALL)
 
 # Chunk I/O
 FLB_OPTION(CIO_LIB_STATIC  ON)
@@ -609,6 +610,7 @@ if(FLB_WASM)
           _Atomic int a;
           return 0;
        }" FLB_HAVE_STDATOMIC_H)
+    include(CheckIncludeFiles)
     check_include_files(stdatomic.h FLB_HAVE_STDATOMIC_H)
     if (FLB_HAVE_STDATOMIC_H)
       enable_language (ASM)

cmake/cares.cmake

@@ -0,0 +1,20 @@
+# cares cmake
+FLB_OPTION(CARES_STATIC      ON)
+FLB_OPTION(CARES_SHARED      OFF)
+FLB_OPTION(CARES_INSTALL     OFF)
+FLB_OPTION(CARES_BUILD_TESTS OFF)
+FLB_OPTION(CARES_BUILD_TOOLS OFF)
+
+if (FLB_SYSTEM_MACOS)
+  # macOS SDK always has <arpa/nameser.h>.
+  FLB_DEFINITION(CARES_HAVE_ARPA_NAMESER_H)
+endif()
+
+include_directories(
+  ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_CARES}/include
+  ${CMAKE_CURRENT_BINARY_DIR}/${FLB_PATH_LIB_CARES}
+)
+
+add_subdirectory(${FLB_PATH_LIB_CARES})# EXCLUDE_FROM_ALL)
+
+set(LIBCARES_LIBRARIES "c-ares")

cmake/headers.cmake

@@ -32,10 +32,8 @@ include_directories(
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_SNAPPY}
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_CMETRICS}/include
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_CTRACES}/include
-  ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_CARES}/include
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_RING_BUFFER}/lwrb/src/include
 
-  ${CMAKE_CURRENT_BINARY_DIR}/${FLB_PATH_LIB_CARES}
   ${CMAKE_CURRENT_BINARY_DIR}/${FLB_PATH_LIB_JANSSON}/include
   ${CMAKE_CURRENT_BINARY_DIR}/lib/cmetrics
   ${CMAKE_CURRENT_BINARY_DIR}/include

src/CMakeLists.txt

@@ -385,7 +385,7 @@ set(FLB_DEPS
   ${FLB_PLUGINS}
   ${FLB_PROXY_PLUGINS}
   ${extra_libs}
-  c-ares
+  ${LIBCARES_LIBRARIES}
   snappy-c
   lwrb
   ${NGHTTP2_LIBRARIES}