How do I link to the locally installed librdkafka in my own projects CMake?

Question

I have installed rdkafka locally on my machine via the apt package manager as instructed in their documentation. Now I want to link to that library with CMake so I can use it.

I am currently trying it like this:

find_package(PkgConfig REQUIRED)
pkg_check_modules(rdkafka REQUIRED rdkafka)
target_include_directories(myTarget PUBLIC ${RDKAFKA_INCLUDE_DIRS})
target_link_libraries(myTarget PUBLIC ${RDKAFKA_LDFLAGS})

It finds the rdkafka library but when trying to build the target it still has undefined references. It does work with the glib library though.

EDIT: This is the output when configuring CMake:

-- Checking for module 'rdkafka'
--   Found rdkafka, version 1.8.0
-- Configuring done
-- Generating done
-- Build files have been written to:

Starting the build leads to this:

/usr/bin/ld: CMakeFiles/OPCKafkaBridge.dir/opc_kafka_bridge.c.o: in function `g_autoptr_cleanup_generic_gfree':
opc_kafka_bridge.c:(.text+0x6c6): undefined reference to `g_free'
/usr/bin/ld: CMakeFiles/OPCKafkaBridge.dir/opc_kafka_bridge.c.o: in function `glib_autoptr_clear_GError':
opc_kafka_bridge.c:(.text+0x6e8): undefined reference to `g_error_free'
/usr/bin/ld: CMakeFiles/OPCKafkaBridge.dir/opc_kafka_bridge.c.o: in function `glib_autoptr_clear_GKeyFile':
opc_kafka_bridge.c:(.text+0x726): undefined reference to `g_key_file_unref'
/usr/bin/ld: CMakeFiles/OPCKafkaBridge.dir/opc_kafka_bridge.c.o: in function `load_config_group':
opc_kafka_bridge.c:(.text+0x7a8): undefined reference to `g_key_file_get_keys'
/usr/bin/ld: opc_kafka_bridge.c:(.text+0x7eb): undefined reference to `g_log'
/usr/bin/ld: opc_kafka_bridge.c:(.text+0x822): undefined reference to `g_key_file_get_string'
/usr/bin/ld: opc_kafka_bridge.c:(.text+0x861): undefined reference to `g_log'
/usr/bin/ld: opc_kafka_bridge.c:(.text+0x8b9): undefined reference to `g_log'
/usr/bin/ld: CMakeFiles/OPCKafkaBridge.dir/opc_kafka_bridge.c.o: in function `dr_msg_cb':
opc_kafka_bridge.c:(.text+0x95b): undefined reference to `g_log'
/usr/bin/ld: CMakeFiles/OPCKafkaBridge.dir/opc_kafka_bridge.c.o: in function `sendKafkaMessage':
opc_kafka_bridge.c:(.text+0x9a4): undefined reference to `g_key_file_new'
/usr/bin/ld: opc_kafka_bridge.c:(.text+0x9d0): undefined reference to `g_key_file_load_from_file'
/usr/bin/ld: opc_kafka_bridge.c:(.text+0xa00): undefined reference to `g_log'
/usr/bin/ld: opc_kafka_bridge.c:(.text+0xaa0): undefined reference to `g_log'
/usr/bin/ld: opc_kafka_bridge.c:(.text+0xbc5): undefined reference to `g_log'
/usr/bin/ld: opc_kafka_bridge.c:(.text+0xc03): undefined reference to `g_log'
/usr/bin/ld: opc_kafka_bridge.c:(.text+0xc4e): undefined reference to `g_log'
/usr/bin/ld: CMakeFiles/OPCKafkaBridge.dir/opc_kafka_bridge.c.o:opc_kafka_bridge.c:(.text+0xca4): more undefined references to `g_log' follow
collect2: error: ld returned 1 exit status
gmake[2]: *** [CMakeFiles/OPCKafkaBridge.dir/build.make:98: OPCKafkaBridge] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/OPCKafkaBridge.dir/all] Error 2
gmake: *** [Makefile:91: all] Error 2

I managed to get it to compile by creating a Makefile manually with the following contents:

CFLAGS=-Wall $(shell pkg-config --cflags glib-2.0 rdkafka)
LDLIBS=$(shell pkg-config --libs glib-2.0 rdkafka)

I hope someone can help me configure should there be a mistake with the way I am trying to link to the library or point me in the right direction if it's correct and the problem is something different.

Ah yeah it's typo in this post and not in the CMakeList file... — Sebastian, Feb 10 '23 at 08:08
There may be some good answers here: https://stackoverflow.com/q/36868143/5264491 — Ian Abbott, Feb 10 '23 at 10:52
Linking GLIB worked just fine. I tried linking rdkafka the same way but it just is not working. — Sebastian, Feb 13 '23 at 16:27

score 0 · Answer 1 · answered Feb 09 '23 at 18:07

librdkafka provides a CMake config file and pkg-config files, so you have 2 solutions:

find_package(RdKafka REQUIRED)
target_link_libraries(myTarget PUBLIC RdKafka::rdkafka)

or

find_package(PkgConfig REQUIRED)
pkg_check_modules(rdkafka REQUIRED IMPORTED_TARGET rdkafka)
target_link_libraries(myTarget PUBLIC PkgConfig::rdkafka)

if you want to link rdkafka++:

find_package(RdKafka REQUIRED)
target_link_libraries(myTarget PUBLIC RdKafka::rdkafka++)

or

find_package(PkgConfig REQUIRED)
pkg_check_modules(rdkafka++ REQUIRED IMPORTED_TARGET rdkafka++)
target_link_libraries(myTarget PUBLIC PkgConfig::rdkafka++)

Sadly this leads to the same problem. When configuring CMake with the CMakeList.txt it reports it has found rdkafka and even lists its version but still fails the build. — Sebastian, Feb 13 '23 at 16:24

How do I link to the locally installed librdkafka in my own projects CMake?

1 Answers1