Linker error compiling mex with mingw-w64

Question

I\'m trying to setup Mingw-w64 as the mex compiler in MATLAB 2013a. My laptop has x86_64 architecture and runs windows 7. The program I want to compile uses c++11-style thre

Answer 1

Note these error messages:

C:\Users\Bas\AppData\Local\Temp\cc4hwD3A.o:Gomoku_mex.cpp:(.text+0x9d1c): undefined reference to `mxGetPr' 
C:\Users\Bas\AppData\Local\Temp\cc4hwD3A.o:Gomoku_mex.cpp:(.text+0x9d83): undefined reference to `mxCreateDoubleScalar'

The library search path for libmex, libmx, libmat, ... is not added in your link command. The directory in your script is the bin directory containing DLLs. That's not correct here.

LINKFLAGS  =  -shared mex.def -L"C:\Program Files\MATLAB\R2013a\extern\lib\win64\microsoft" -static-libstdc++ 

Answer 2

Take the following configuration file that I'm using (you'll need to adjust the path pointing to MinGW-w64 location accordingly):

mingw_mexopts.bat

@echo off

set MATLAB=%MATLAB%
set MW_TARGET_ARCH=win64
set PATH=C:\MinGW-w64\mingw64\bin;%PATH%

set COMPILER=x86_64-w64-mingw32-g++
set COMPFLAGS=-c -m64 -mwin32 -mdll -Wall -std=c++11 -DMATLAB_MEX_FILE
set OPTIMFLAGS=-DNDEBUG -O2
set DEBUGFLAGS=-g
set NAME_OBJECT=-o

set LINKER=x86_64-w64-mingw32-g++
set LINKFLAGS=-shared -L"%MATLAB%\extern\lib\win64\microsoft" -L"%MATLAB%\bin\win64"
set LINKFLAGSPOST=-lmx -lmex -lmat
set LINKOPTIMFLAGS=-O2
set LINKDEBUGFLAGS=-g
set LINK_FILE=
set LINK_LIB=
set NAME_OUTPUT=-o "%OUTDIR%%MEX_NAME%%MEX_EXT%"

Next here is a simple MEX-function that uses C++11 threads:

test.cpp

#include "mex.h"
#include <vector>
#include <thread>

void say_hello(int tid) {
    mexPrintf("hello from %d\n", tid);
}

void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
    std::vector<std::thread> threads;
    for (int i=0; i<10; i++) {
        threads.push_back(std::thread(say_hello, i));
    }        
    for(auto& t : threads) {
        t.join();
    }
}

Finally we compile and run it in MATLAB:

>> mex -f mingw_mexopts.bat -largeArrayDims test.cpp

>> setenv('PATH', ['C:\MinGW-w64\mingw64\bin;', getenv('PATH')])

>> test
hello from 0
hello from 4
hello from 2
hello from 3
hello from 5
hello from 1
hello from 6
hello from 8
hello from 7
hello from 9

Note that if you're going to deploy this to another machine, you'll have to also copy a few dependent DLL's (you'll find them in MinGW bin folder), and place them next to the MEX-file. Use Dependency Walker to list them. In my case it was:

• libstdc++-6.dll
• libgcc_s_seh-1.dll
• libwinpthread-1.dll

I am using GCC 4.8.2 with MATLAB R2014a running on 64-bit Windows.