I would like to cross compile C++ projects for Windows 64 bit from Linux using the mingw-w64 tools (Actually I am using M Cross Environment which is based on mingw-w64, but I don't think this is relevant to the question). In my case the final step requires linking to several third party compiled dlls. I do not have the source code of these dlls, only the header files and compiled binary Compiled using what? I do not know but likely Visual Studio.
To explain exactly what I am doing, I want to cross-compile Matlab mex files from Linux and need to link to the Matlab libraries libmex.dll, libmx.dll and libmat.dll. However, I don't think any Matlab knowledge is required to answer the question.
I am vaguely aware that I need to extract definitions from the dlls, into .def files, and maybe that I need to create another link library of some kind to actually link to.
I have attempted both of these steps, first the creation of definition files for each library, which I did with the following command:
gendef libmx.dll
Here's a snippet of the resulting definition file libmx.def
;
; Definition file of libmx.dll
; Automatic generated by gendef
; written by Kai Tietz 2008
;
LIBRARY "libmx.dll"
EXPORTS
; public: __cdecl <struct mxArray_tag,class Mprotected_mxArray_helper>::<struct mxArray_tag,class Mprotected_mxArray_helper>(class <struct mxArray_tag,class Mprotected_mxArray_helper> const &__ptr64 )__ptr64
??0?$Mprotected_cptr@UmxArray_tag@@VMprotected_mxArray_helper@@@@QEAA@AEBV0@@Z
; public: __cdecl <struct mxArray_tag,class Mprotected_mxArray_helper>::<struct mxArray_tag,class Mprotected_mxArray_helper>(struct mxArray_tag *__ptr64,bool)__ptr64
??0?$Mprotected_cptr@UmxArray_tag@@VMprotected_mxArray_helper@@@@QEAA@PEAUmxArray_tag@@_N@Z
; public: __cdecl <struct mxArray_tag,class Mprotected_mxArray_helper>::<struct mxArray_tag,class Mprotected_mxArray_helper>(void)__ptr64
??0?$Mprotected_cptr@UmxArray_tag@@VMprotected_mxArray_helper@@@@QEAA@XZ
; public: __cdecl matrix::serialize::Exception::Exception(class matrix::serialize::Exception const &__ptr64 )__ptr64
??0Exception@serialize@matrix@@QEAA@AEBV012@@Z
; public: __cdecl matrix::serialize::Exception::Exception(int,__int64)__ptr64
??0Exception@serialize@matrix@@QEAA@H_J@Z
; public: __cdecl matrix::serialize::FailedUCNV::FailedUCNV(class matrix::serialize::FailedUCNV const &__ptr64 )__ptr64
??0FailedUCNV@serialize@matrix@@QEAA@AEBV012@@Z
; public: __cdecl matrix::serialize::FailedUCNV::FailedUCNV(int,__int64,int)__ptr64
??0FailedUCNV@serialize@matrix@@QEAA@H_JH@Z
; public: __cdecl Mprotected_mxArray::Mprotected_mxArray(class Mprotected_mxArray const &__ptr64 )__ptr64
??0Mprotected_mxArray@@QEAA@AEBV0@@Z
; public: __cdecl Mprotected_mxArray::Mprotected_mxArray(struct mxArray_tag *__ptr64,bool)__ptr64
??0Mprotected_mxArray@@QEAA@PEAUmxArray_tag@@_N@Z
; public: __cdecl Mprotected_mxArray::Mprotected_mxArray(void)__ptr64
??0Mprotected_mxArray@@QEAA@XZ
; public: __cdecl RRTableVisitor::RRTableVisitor(class RRTableVisitor const &__ptr64 )__ptr64
??0RRTableVisitor@@QEAA@AEBV0@@Z
I then attempted to create an import library based on the instructions provided for Mingw here. However, as I am using mingw-w64 my command was actually
x86_64-w64-mingw32.static-dlltool -d libmx.def -l libmx.a
However, when I attempt to build a simple example linked to these libraries, I get an error. Here is the actual commands used to build and link the libs.
/opt/mxe/usr/bin/x86_64-w64-mingw32.static-gcc -c -I/usr/local/MATLAB/R2015a/extern/include -I/usr/local/MATLAB/R2015a/simulink/include -DMATLAB_MEX_FILE -std=c99 -D_GNU_SOURCE -fexceptions -fPIC -fno-omit-frame-pointer -pthread -I/opt/mxe/usr/bin/include -DMX_COMPAT_32 -O -DNDEBUG "/home/rcrozier/yprime.c"
/opt/mxe/usr/bin/x86_64-w64-mingw32.static-gcc -O -L/home/rcrozier/Sync/work/matlab_windows_libs/r2013a -L/opt/mxe/usr/bin/lib -pthread -Wl,--version-script,/usr/local/MATLAB/R2015a/extern/lib/glnxa64/mexFunction.map -Wl,--no-undefined -I/usr/local/MATLAB/R2015a/extern/include -o "yprime.mexw64" yprime.o -Wl,-rpath-link -L/home/rcrozier/Sync/work/matlab_windows_libs/r2013a -lmx -lmex -lmat -L/opt/mxe/usr/bin/lib -lm -lstdc++
The compile step goes ok, but the linking step fails with the following error:
yprime.o:yprime.c:(.text+0x53): undefined reference to `mxGetM'
yprime.o:yprime.c:(.text+0x5f): undefined reference to `mxGetN'
yprime.o:yprime.c:(.text+0x6b): undefined reference to `mxIsDouble'
yprime.o:yprime.c:(.text+0x78): undefined reference to `mxIsComplex'
yprime.o:yprime.c:(.text+0xbe): undefined reference to `mxCreateDoubleMatrix_700'
yprime.o:yprime.c:(.text+0xca): undefined reference to `mxGetPr'
yprime.o:yprime.c:(.text+0xd5): undefined reference to `mxGetPr'
yprime.o:yprime.c:(.text+0xde): undefined reference to `mxGetPr'
/opt/mxe/usr/lib/gcc/x86_64-w64-mingw32.static/4.9.4/../../../../x86_64-w64-mingw32.static/lib/../lib/libmingw32.a(lib64_libmingw32_a-crt0_c.o): In function `main':
/opt/mxe/tmp-gcc-x86_64-w64-mingw32.static/gcc-4.9.4/mingw-w64-v4.0.6/mingw-w64-crt/crt/crt0_c.c:18: undefined reference to `WinMain'
collect2: error: ld returned 1 exit status
I am happy for the result of this compilation to be statically linked.
So my question is, what exactly do I have to do to link to third party dlls when cross-compiling for Windows from Linux, and why might the linking step be failing in this case?
By the way, this particular example is for a simple C file example, in reality I will also want to link C++ files. Feel free to point out any obvious flaws in my process related to being confused about C and C++ build processes!
