lib: librdkafka: cmake: allow compilation without CXX support

e.g. fluent-bit is a c-only library, so allow compilation without cxx

See: confluentinc/librdkafka#4366
Signed-off-by: Thomas Devoogdt <[email protected]>

Author: ThomasDevoogdt

lib/librdkafka-2.8.0/CMakeLists.txt

@@ -3,7 +3,16 @@ cmake_minimum_required(VERSION 3.5)
 include("packaging/cmake/parseversion.cmake")
 parseversion("src/rdkafka.h")
 
-project(RdKafka VERSION ${RDKAFKA_VERSION})
+project(RdKafka VERSION ${RDKAFKA_VERSION} LANGUAGES C)
+
+# Check for CXX support
+include(CheckLanguage)
+check_language(CXX)
+if(CMAKE_CXX_COMPILER)
+  enable_language(CXX)
+else()
+  message(STATUS "C++ compiler not found, skipping C++ support")
+endif()
 
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_CURRENT_SOURCE_DIR}/packaging/cmake/Modules/")
 
@@ -181,7 +190,11 @@ endif()
 
 option(RDKAFKA_BUILD_STATIC "Build static rdkafka library" OFF)
 option(RDKAFKA_BUILD_EXAMPLES "Build examples" ON)
-option(RDKAFKA_BUILD_TESTS "Build tests" ON)
+
+if(CMAKE_CXX_COMPILER)
+    option(RDKAFKA_BUILD_TESTS "Build tests" ON)
+endif()
+
 if(WIN32)
     option(WITHOUT_WIN32_CONFIG "Avoid including win32_config.h on cmake builds" ON)
 endif(WIN32)
@@ -279,7 +292,10 @@ install(
 )
 
 add_subdirectory(src)
-add_subdirectory(src-cpp)
+
+if(CMAKE_CXX_COMPILER)
+  add_subdirectory(src-cpp)
+endif()
 
 if(RDKAFKA_BUILD_EXAMPLES)
   add_subdirectory(examples)

lib/librdkafka-2.8.0/examples/CMakeLists.txt

@@ -5,23 +5,31 @@ endif(WIN32)
 add_executable(producer producer.c ${win32_sources})
 target_link_libraries(producer PUBLIC rdkafka)
 
-add_executable(producer_cpp producer.cpp ${win32_sources})
-target_link_libraries(producer_cpp PUBLIC rdkafka++)
+if(CMAKE_CXX_COMPILER)
+    add_executable(producer_cpp producer.cpp ${win32_sources})
+    target_link_libraries(producer_cpp PUBLIC rdkafka++)
+endif()
 
 add_executable(consumer consumer.c ${win32_sources})
 target_link_libraries(consumer PUBLIC rdkafka)
 
 add_executable(rdkafka_performance rdkafka_performance.c ${win32_sources})
 target_link_libraries(rdkafka_performance PUBLIC rdkafka)
 
-add_executable(rdkafka_example_cpp rdkafka_example.cpp ${win32_sources})
-target_link_libraries(rdkafka_example_cpp PUBLIC rdkafka++)
+if(CMAKE_CXX_COMPILER)
+    add_executable(rdkafka_example_cpp rdkafka_example.cpp ${win32_sources})
+    target_link_libraries(rdkafka_example_cpp PUBLIC rdkafka++)
+endif()
 
-add_executable(rdkafka_complex_consumer_example_cpp rdkafka_complex_consumer_example.cpp ${win32_sources})
-target_link_libraries(rdkafka_complex_consumer_example_cpp PUBLIC rdkafka++)
+if(CMAKE_CXX_COMPILER)
+    add_executable(rdkafka_complex_consumer_example_cpp rdkafka_complex_consumer_example.cpp ${win32_sources})
+    target_link_libraries(rdkafka_complex_consumer_example_cpp PUBLIC rdkafka++)
+endif()
 
-add_executable(openssl_engine_example_cpp openssl_engine_example.cpp ${win32_sources})
-target_link_libraries(openssl_engine_example_cpp PUBLIC rdkafka++)
+if(CMAKE_CXX_COMPILER)
+    add_executable(openssl_engine_example_cpp openssl_engine_example.cpp ${win32_sources})
+    target_link_libraries(openssl_engine_example_cpp PUBLIC rdkafka++)
+endif()
 
 add_executable(misc misc.c ${win32_sources})
 target_link_libraries(misc PUBLIC rdkafka)
@@ -73,7 +81,8 @@ if(NOT WIN32)
     add_executable(rdkafka_complex_consumer_example rdkafka_complex_consumer_example.c)
     target_link_libraries(rdkafka_complex_consumer_example PUBLIC rdkafka)
 
-    add_executable(kafkatest_verifiable_client kafkatest_verifiable_client.cpp)
-    target_link_libraries(kafkatest_verifiable_client PUBLIC rdkafka++)
-
+    if(CMAKE_CXX_COMPILER)
+        add_executable(kafkatest_verifiable_client kafkatest_verifiable_client.cpp)
+        target_link_libraries(kafkatest_verifiable_client PUBLIC rdkafka++)
+    endif()
 endif(NOT WIN32)