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I am trying to build my Project using cmake. With 3rd Party headerfiles and libarys. The headers are in /usr/local/include/ and the libary in /usr/local/lib/. And I think the compiler finds the files because I get no error on the includes but when I try to compile it it doesn´t find the functions I´m calling.

/mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:12: undefined reference to `ola::InitLogging(ola::log_level, ola::log_output)'
/usr/bin/ld: /mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:13: undefined reference to `ola::DmxBuffer::DmxBuffer()'
/usr/bin/ld: /mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:14: undefined reference to `ola::DmxBuffer::Blackout()'
/usr/bin/ld: /mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:17: undefined reference to `ola::client::StreamingClient::StreamingClient(ola::client::StreamingClient::Options const&)'
/usr/bin/ld: /mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:19: undefined reference to `ola::client::StreamingClient::Setup()'
/usr/bin/ld: /mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:26: undefined reference to `ola::DmxBuffer::SetChannel(unsigned int, unsigned char)'
/usr/bin/ld: /mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:27: undefined reference to `ola::client::StreamingClient::SendDmx(unsigned int, ola::DmxBuffer const&)'
/usr/bin/ld: /mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:34: undefined reference to `ola::client::StreamingClient::~StreamingClient()'
/usr/bin/ld: /mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:34: undefined reference to `ola::DmxBuffer::~DmxBuffer()'
/usr/bin/ld: /mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:34: undefined reference to `ola::client::StreamingClient::~StreamingClient()'
/usr/bin/ld: /mnt/c/Users/Max/CLionProjects/Lightning_Controller/main.cpp:34: undefined reference to `ola::DmxBuffer::~DmxBuffer()'
collect2: error: ld returned 1 exit status

If I compile it with G++ and this parameters g++ main.cpp -lola -lolacommon -lprotobuf it works.

I tried to use the Option Mentioned in this Post but it didn´t change anything.

My Question is how do i translate this from g++ to cmake ?

Smxas
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1 Answers1

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It would be nice to have more information about what you are doing, but this is what I have for you.

The compiler can't find the implementation for the functions you're calling. It finds the headers, but it doesn't link the library with the actual implementations. With CMake, specify the libraries to link.

I don't know what version of C++ you are on, so change it accordingly.

cmake_minimum_required(VERSION 3.10)
project(Lightning_Controller)

set(CMAKE_CXX_STANDARD 14)

include_directories(/usr/local/include/)

add_executable(Lightning_Controller main.cpp)

link_directories(/usr/local/lib/)

target_link_libraries(Lightning_Controller ola olacommon protobuf)
Ben A.
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  • Thank you very much. The missing part was the `target_link_libraries`. – Smxas Aug 05 '23 at 22:19
  • I prefer the use of `target_include_directories` and `target_link_directories` to the commands applying to any target defined afterwards; It's just easier to reason about the targets it affects, if the choice is made on a per-target basis (and possibly "inherited" by linking targets). For the same reason I prefer the use of `target_compile_features(Ligntning_Controller PRIVATE cxx_std_14)` to `set(CMAKE_CXX_STANDARD 14)` – fabian Aug 06 '23 at 10:21