R2017b CMakeFile problem with Matlab Engine

Hi there,

I need to buid a c++ code that includes some matlab engine features. Before doing that, I wanted to test with a simpler example: https://github.com/niosus/Matlab-Engine-CMake-Test

Instead of using custom cmake/FindMatlab.cmake in the original repo, I used FINDMATLAB command provided by Cmake 3.13.4. Here is the directory structure of the project:

Versions: MATLAB R2017b, CMake 3.13.4, Ubuntu 16.04.

- bin
   -- test_function.m
- build (cmake)  
- CMakeLists.txt  (CMakeLists #1)
- README.md  
- src
   -- matlab_engine.cpp (https://github.com/niosus/Matlab-Engine-CMake-Test/blob/master/src/matlab_engine.cpp)
   -- CMakeLists.txt (CMakeLists #2)

CMakeLists #1

cmake_minimum_required(VERSION 2.8)
project(MEX)

set(CMAKE_INSTALL_PREFIX ${CMAKE_SOURCE_DIR})
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/bin)
set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake)

find_package(Matlab REQUIRED ENG_LIBRARY MX_LIBRARY MAT_LIBRARY)

IF(MATLAB_FOUND)
    message(STATUS "MATLAB Found, MATLAB MEX will be compiled.")
    add_subdirectory(src)
ELSE(MATLAB_FOUND)
    MESSAGE("MATLAB not found...nothing will be built.")
ENDIF(MATLAB_FOUND)

include_directories(${Matlab_INCLUDE_DIRS})
target_link_libraries(mat_engine ${MATLAB_ENG_LIBRARY} ${MATLAB_MX_LIBRARY} ${MATLAB_MAT_LIBRARY})

SET(CMAKE_CXX_FLAGS "-std=c++11")

CMakeLists #2

include_directories(${Matlab_INCLUDE_DIRS})
link_directories(${Matlab_LIBRARIES} ${MATLAB_ENG_LIBRARY})

add_executable (mat_engine matlab_engine.cpp)

target_link_libraries(mat_engine ${MATLAB_MAT_LIBRARY} ${MATLAB_ENG_LIBRARY} ${MATLAB_MX_LIBRARY})

message(STATUS ${MATLAB_ENG_LIBRARY})
message(STATUS ${MATLAB_MAT_LIBRARY})

SET(CMAKE_VERBOSE_MAKEFILE ON)

SET(CMAKE_CXX_FLAGS "-std=c++11")

Note that I can execute following command in MATLAB successfully:

mex -v GCC='/usr/bin/g++-4.9' -client engine matlab_engine.cpp 

Although I make sure that I am using the correct g++ version for R2017b (4.9), I run into following error:

/usr/bin/g++-4.9  -std=c++11  -rdynamic CMakeFiles/mat_engine.dir/matlab_engine.cpp.o  -o ../../bin/mat_engine  -L/usr/local/MATLAB/R2017b/bin/glnxa64/libmex.so  -L/usr/local/MATLAB/R2017b/bin/glnxa64/libmx.so  -L/usr/local/MATLAB/R2017b/bin/glnxa64/libeng.so  -L/usr/local/MATLAB/R2017b/bin/glnxa64/libmat.so 
CMakeFiles/mat_engine.dir/matlab_engine.cpp.o: In function `main':
matlab_engine.cpp:(.text+0x20): undefined reference to `mxCreateDoubleMatrix'
matlab_engine.cpp:(.text+0x38): undefined reference to `mxCreateDoubleMatrix'
matlab_engine.cpp:(.text+0x48): undefined reference to `mxGetData'
matlab_engine.cpp:(.text+0x58): undefined reference to `mxGetData'
matlab_engine.cpp:(.text+0x88): undefined reference to `engOpen'
matlab_engine.cpp:(.text+0xd5): undefined reference to `engPutVariable'
matlab_engine.cpp:(.text+0xea): undefined reference to `engPutVariable'
matlab_engine.cpp:(.text+0xfb): undefined reference to `engEvalString'
matlab_engine.cpp:(.text+0x10c): undefined reference to `engGetVariable'
matlab_engine.cpp:(.text+0x11c): undefined reference to `mxGetData'
collect2: error: ld returned 1 exit status
src/CMakeFiles/mat_engine.dir/build.make:86: recipe for target '../bin/mat_engine' failed
make[2]: *** [../bin/mat_engine] Error 1
CMakeFiles/Makefile2:90: recipe for target 'src/CMakeFiles/mat_engine.dir/all' failed
make[1]: *** [src/CMakeFiles/mat_engine.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2

I'd be greatful if someone can point out the problem and offer a solution. It seems like there is not a problem with linking target libraries, yet executable cannot be created.

Answer 1

[sina valipoor]

Hi i had the same issue and manage to fix it.

1) check this page : https://nl.mathworks.com/help/matlab/matlab_external/mat-file-library-and-include-files.html

Here you see you will need to link the following libraries;

1.1)libmat.so 1.2)libmx.so , specially your error coming from missing libmx.so the matrix library.

2) check this page: https://nl.mathworks.com/help/matlab/matlab_external/building-on-unix-operating-systems.html

you need to add the (Linux) export LD_LIBRARY_PATH = matlabroot/bin/glnxa64:matlabroot/sys/os/glnxa64

to your env, or rather in your ~/.profile file.

This 2 steps will fix the errors you have.