How to call Matlab form C++ code?

Question

I am trying to call Matlab functions form C++ code.

With Matlab it comes an example of such code at /extern/examples/eng_mat/engdemo.cpp, however I found no way to build that source code.

Here is the makefile I use:

CFLAGS = -Wall -O3

INCLUDES = -I/opt/Matlab-2009a/extern/include

LIBRARIES = -Wl,-R/opt/Matlab-2009a/bin/glnx86 -L/opt/Matlab-2009a/bin/glnx86 -lmx -lmat -leng

out : engdemo.cpp
    g++ $(CFLAGS) $(INCLUDES) -static $^ $(LIBRARIES) -o out

clean :
    rm -f out

(Here /opt/Matlab-2009a is my Matlab root.) I am getting a linker error like this:

/usr/bin/ld: cannot find -lmx
collect2: ld returned 1 exit status
make: *** [out] Error 1

And the question is: how can I make g++ to compile engdemo.cpp ?

Note, that the shared library exists:

$ locate libmx.so
/opt/Matlab-2009a/bin/glnx86/libmx.so
/opt/Matlab-2009a/bin/glnx86/libmx.so.csf

and

$ ldd /opt/Matlab-2009a/bin/glnx86/libmx.so
    linux-gate.so.1 =>  (0x004b4000)
    libut.so => /opt/Matlab-2009a/bin/glnx86/../../bin/glnx86/libut.so (0x0078f000)
    libmwfl.so => /opt/Matlab-2009a/bin/glnx86/../../bin/glnx86/libmwfl.so (0x00110000)
    libicudata.so.38 => /opt/Matlab-2009a/bin/glnx86/../../bin/glnx86/libicudata.so.38 (0xb7f82000)
    libicuuc.so.38 => /opt/Matlab-2009a/bin/glnx86/../../bin/glnx86/libicuuc.so.38 (0x00bee000)
    libicui18n.so.38 => /opt/Matlab-2009a/bin/glnx86/../../bin/glnx86/libicui18n.so.38 (0x001f7000)
    libicuio.so.38 => /opt/Matlab-2009a/bin/glnx86/../../bin/glnx86/libicuio.so.38 (0x00e1c000)
    libz.so.1 => /usr/lib/libz.so.1 (0x0098e000)
    libstdc++.so.6 => /opt/Matlab-2009a/bin/glnx86/../../sys/os/glnx86/libstdc++.so.6 (0x00531000)
    libm.so.6 => /lib/libm.so.6 (0x00194000)
    libgcc_s.so.1 => /opt/Matlab-2009a/bin/glnx86/../../sys/os/glnx86/libgcc_s.so.1 (0x00eaa000)
    libpthread.so.0 => /lib/libpthread.so.0 (0x00900000)
    libc.so.6 => /lib/libc.so.6 (0x00345000)
    librt.so.1 => /lib/librt.so.1 (0x00964000)
    libdl.so.2 => /lib/libdl.so.2 (0x0014e000)
    libexpat.so.1 => /opt/Matlab-2009a/bin/glnx86/../../bin/glnx86/../../bin/glnx86/libexpat.so.1 (0x00152000)
    libboost_thread-gcc42-mt-1_36.so.1.36.0 => /opt/Matlab-2009a/bin/glnx86/../../bin/glnx86/../../bin/glnx86/libboost_thread-gcc42-mt-1_36.so.1.36.0 (0x00fc2000)
    libboost_signals-gcc42-mt-1_36.so.1.36.0 => /opt/Matlab-2009a/bin/glnx86/../../bin/glnx86/../../bin/glnx86/libboost_signals-gcc42-mt-1_36.so.1.36.0 (0x0017d000)
    libboost_system-gcc42-mt-1_36.so.1.36.0 => /opt/Matlab-2009a/bin/glnx86/../../bin/glnx86/../../bin/glnx86/libboost_system-gcc42-mt-1_36.so.1.36.0 (0x00a06000)
    /lib/ld-linux.so.2 (0x001db000)

So, how can I make g++ to compile engdemo.cpp ?

Answer 1

Assuming $MATLABROOT is the path to MATLAB:

$MATLABROOT/bin/mex -f $MATLABROOT/bin/engopts.sh engdemo.cpp

If you add the -v switch, the verbose output will show you what commands are being used to compile the engine application.

Answer 2

Why are you compiling with -static? From "man gcc":

-static On systems that support dynamic linking, this prevents linking with the shared libraries. On other systems, this option has no effect.

In other words, the -static option forces the linker to only consider static libraries, meaning that it will try to find libmx.a rather than libmx.so. Since Matlab only ships with shared (dynamic) libraries, it fails.

Try removing that option & see what happens.

If that doesn't work, you may need to run libtool to help it find the .so's at runtime.