GH-48091: [C++] Use FetchContent for bundled c-ares

Author: raulcd

cpp/cmake_modules/ThirdpartyToolchain.cmake

@@ -2951,32 +2951,68 @@ if(ARROW_WITH_UTF8PROC)
 endif()
 
 macro(build_cares)
-  message(STATUS "Building c-ares from source")
+  message(STATUS "Building c-ares from source using FetchContent")
+  set(CARES_VENDORED TRUE)
   set(CARES_PREFIX "${CMAKE_CURRENT_BINARY_DIR}/cares_ep-install")
-  set(CARES_INCLUDE_DIR "${CARES_PREFIX}/include")
 
-  # If you set -DCARES_SHARED=ON then the build system names the library
-  # libcares_static.a
-  set(CARES_STATIC_LIB
-      "${CARES_PREFIX}/lib/${CMAKE_STATIC_LIBRARY_PREFIX}cares${CMAKE_STATIC_LIBRARY_SUFFIX}"
-  )
+  # Configure c-ares options before FetchContent
+  set(CARES_SHARED OFF)
+  set(CARES_STATIC ON)
+  set(CARES_INSTALL ON)
+  set(CARES_BUILD_TOOLS OFF)
+  set(CARES_BUILD_TESTS OFF)
 
-  set(CARES_CMAKE_ARGS "${EP_COMMON_CMAKE_ARGS}" "-DCMAKE_INSTALL_PREFIX=${CARES_PREFIX}"
-                       -DCARES_SHARED=OFF -DCARES_STATIC=ON)
+  fetchcontent_declare(cares
+                       URL ${CARES_SOURCE_URL}
+                       URL_HASH "SHA256=${ARROW_CARES_BUILD_SHA256_CHECKSUM}")
 
-  externalproject_add(cares_ep
-                      ${EP_COMMON_OPTIONS}
-                      URL ${CARES_SOURCE_URL}
-                      URL_HASH "SHA256=${ARROW_CARES_BUILD_SHA256_CHECKSUM}"
-                      CMAKE_ARGS ${CARES_CMAKE_ARGS}
-                      BUILD_BYPRODUCTS "${CARES_STATIC_LIB}")
+  prepare_fetchcontent()
 
-  file(MAKE_DIRECTORY ${CARES_INCLUDE_DIR})
+  set(CMAKE_INSTALL_PREFIX_SAVED "${CMAKE_INSTALL_PREFIX}")
+  set(CMAKE_INSTALL_PREFIX "${CARES_PREFIX}")
+  fetchcontent_makeavailable(cares)
 
-  add_library(c-ares::cares STATIC IMPORTED)
-  set_target_properties(c-ares::cares PROPERTIES IMPORTED_LOCATION "${CARES_STATIC_LIB}")
-  target_include_directories(c-ares::cares BEFORE INTERFACE "${CARES_INCLUDE_DIR}")
-  add_dependencies(c-ares::cares cares_ep)
+  # Restore original install prefix
+  set(CMAKE_INSTALL_PREFIX "${CMAKE_INSTALL_PREFIX_SAVED}")
+  cleanup_fetchcontent()
+
+  # gRPC requires c-ares to be installed to a known location.
+  # We have to do this in two steps to avoid double installation of c-ares
+  # when Arrow is installed.
+  # This custom target ensures c-ares is built before we install
+  add_custom_target(cares_built DEPENDS c-ares::cares)
+
+  # Disable c-ares's install script after it's built to prevent double installation
+  add_custom_command(OUTPUT "${cares_BINARY_DIR}/cmake_install.cmake.saved"
+                     COMMAND ${CMAKE_COMMAND} -E copy_if_different
+                             "${cares_BINARY_DIR}/cmake_install.cmake"
+                             "${cares_BINARY_DIR}/cmake_install.cmake.saved"
+                     COMMAND ${CMAKE_COMMAND} -E echo
+                             "# c-ares install disabled to prevent double installation with Arrow"
+                             > "${cares_BINARY_DIR}/cmake_install.cmake"
+                     DEPENDS cares_built
+                     COMMENT "Disabling c-ares install to prevent double installation"
+                     VERBATIM)
+
+  add_custom_target(cares_install_disabled ALL
+                    DEPENDS "${cares_BINARY_DIR}/cmake_install.cmake.saved")
+
+  # Install c-ares to CARES_PREFIX for gRPC to find
+  add_custom_command(OUTPUT "${CARES_PREFIX}/.cares_installed"
+                     COMMAND ${CMAKE_COMMAND} -E copy_if_different
+                             "${cares_BINARY_DIR}/cmake_install.cmake.saved"
+                             "${cares_BINARY_DIR}/cmake_install.cmake.tmp"
+                     COMMAND ${CMAKE_COMMAND} -DCMAKE_INSTALL_PREFIX=${CARES_PREFIX}
+                             -DCMAKE_INSTALL_CONFIG_NAME=$<CONFIG> -P
+                             "${cares_BINARY_DIR}/cmake_install.cmake.tmp" ||
+                             ${CMAKE_COMMAND} -E true
+                     COMMAND ${CMAKE_COMMAND} -E touch "${CARES_PREFIX}/.cares_installed"
+                     DEPENDS cares_install_disabled
+                     COMMENT "Installing c-ares to ${CARES_PREFIX} for gRPC"
+                     VERBATIM)
+
+  # Make cares_ep depend on the install completion marker
+  add_custom_target(cares_ep DEPENDS "${CARES_PREFIX}/.cares_installed")
 
   if(APPLE)
     # libresolv must be linked from c-ares version 1.16.1
@@ -2985,8 +3021,6 @@ macro(build_cares)
                                                    "${LIBRESOLV_LIBRARY}")
   endif()
 
-  set(CARES_VENDORED TRUE)
-
   list(APPEND ARROW_BUNDLED_STATIC_LIBS c-ares::cares)
 endmacro()
 
@@ -3208,8 +3242,16 @@ macro(build_grpc)
   get_filename_component(GRPC_PB_ROOT "${GRPC_PROTOBUF_INCLUDE_DIR}" DIRECTORY)
   get_target_property(GRPC_Protobuf_PROTOC_LIBRARY ${ARROW_PROTOBUF_LIBPROTOC}
                       IMPORTED_LOCATION)
-  get_target_property(GRPC_CARES_INCLUDE_DIR c-ares::cares INTERFACE_INCLUDE_DIRECTORIES)
-  get_filename_component(GRPC_CARES_ROOT "${GRPC_CARES_INCLUDE_DIR}" DIRECTORY)
+
+  # For FetchContent c-ares, use the install prefix directly
+  if(CARES_VENDORED)
+    set(GRPC_CARES_ROOT "${CARES_PREFIX}")
+  else()
+    get_target_property(GRPC_CARES_INCLUDE_DIR c-ares::cares
+                        INTERFACE_INCLUDE_DIRECTORIES)
+    get_filename_component(GRPC_CARES_ROOT "${GRPC_CARES_INCLUDE_DIR}" DIRECTORY)
+  endif()
+
   get_target_property(GRPC_RE2_INCLUDE_DIR re2::re2 INTERFACE_INCLUDE_DIRECTORIES)
   get_filename_component(GRPC_RE2_ROOT "${GRPC_RE2_INCLUDE_DIR}" DIRECTORY)