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lib: librdkafka: only require a C compiler #10341

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lib: librdkafka: only require a C compiler
ThomasDevoogdt Jul 25, 2023
16d53c5
Revert "workflows: exclude librdkafka-dev from pr-compile-without-cxx"
ThomasDevoogdt Oct 4, 2025
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4 changes: 2 additions & 2 deletions .github/workflows/pr-compile-check.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -135,7 +135,7 @@ jobs:
run: |
sudo apt-get update
sudo apt-get install -y bison cmake flex gcc libssl-dev libyaml-dev
sudo apt-get install -y libzstd-dev librdkafka-dev
sudo apt-get install -y libzstd-dev

- name: Install cmake
uses: jwlawson/actions-setup-cmake@v2
Expand All @@ -149,6 +149,6 @@ jobs:
run: |
export CXX=/bin/false
export nparallel=$(( $(getconf _NPROCESSORS_ONLN) > 8 ? 8 : $(getconf _NPROCESSORS_ONLN) ))
cmake -DFLB_PREFER_SYSTEM_LIB_ZSTD=ON -DFLB_PREFER_SYSTEM_LIB_KAFKA=ON ../
cmake -DFLB_PREFER_SYSTEM_LIB_ZSTD=ON ../
make -j $nparallel
working-directory: build
22 changes: 19 additions & 3 deletions lib/librdkafka-2.10.1/CMakeLists.txt
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Expand Up @@ -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()
Comment on lines +9 to +15

@coderabbitai coderabbitai Bot Oct 4, 2025

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⚠️ Potential issue | 🔴 Critical

Handle bogus CXX values before calling enable_language

When CXX is preset to something non-working (e.g. our no-C++ workflow exports /bin/false), check_language(CXX) still leaves CMAKE_CXX_COMPILER pointing at that path instead of *-NOTFOUND. The current if (CMAKE_CXX_COMPILER) conditional therefore fires and enable_language(CXX) aborts configuration, defeating the “C-only” fallback we’re trying to enable. Please tighten the guard so we only enable C++ when CMAKE_CXX_COMPILER is both defined and not *-NOTFOUND. One way is:

-check_language(CXX)
-if(CMAKE_CXX_COMPILER)
+check_language(CXX)
+if(CMAKE_CXX_COMPILER AND NOT CMAKE_CXX_COMPILER MATCHES "-NOTFOUND$")
   enable_language(CXX)
 else()
   message(STATUS "C++ compiler not found, skipping C++ support")
 endif()
🤖 Prompt for AI Agents 
In lib/librdkafka-2.10.1/CMakeLists.txt around lines 9-15, the current guard
uses if(CMAKE_CXX_COMPILER) which can be true for bogus values like /bin/false
left by check_language(CXX), causing enable_language(CXX) to abort; change the
conditional to only enable C++ when the compiler is both defined and not a
NOTFOUND marker, e.g. use if(DEFINED CMAKE_CXX_COMPILER AND NOT
CMAKE_CXX_COMPILER MATCHES "-NOTFOUND$") then enable_language(CXX) else emit the
existing status message.


set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_CURRENT_SOURCE_DIR}/packaging/cmake/Modules/")

Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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)
Expand Down
31 changes: 20 additions & 11 deletions lib/librdkafka-2.10.1/examples/CMakeLists.txt
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Expand Up @@ -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)
Expand Down Expand Up @@ -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)