I’ve received a few emails recently regarding some packages I submitted on Matlab Central that include C code to be compiled into a MEX file. I’ve always developed MEX files with GCC on Linux and my understanding of C is rudimentary. I wasn’t too sure what was necessary to get them to compile on Windows with Visual Studio C++. Users reported that VC++ was giving tons of compilation errors.
Turns out it’s pretty straightforward. The C compiler in VS wants variables to be declared at the top of functions. It’s a very annoying limitation. The solution is change the extension of every .c file to .cpp to get it to compile with the C++ compiler, which has no such limitation. Obviously you’ll need to change #include statements accordingly. C++ is not a strict subset of C, but unless you’re doing something fancy it should compile as is. A nice side effect is that you no longer need to use the -std=c99 flag in GCC to get it to accept C++ // style comments.
I’ve updated mexme accordingly, so you can generate cross-platform MEX files with only a rudimentary understanding of C.
Some other gotchas include differing definitions of various numeric types across platforms (including 32-bit vs. 64-bit). The trick here is to type all non-doubles using the constant that the Mathworks define in mex.h:
UINT8_T UINT16_T UINT32_T UINT64_T INT8_T INT16_T INT32_T INT64_T REAL32_T //AKA single REAL64_T //AKA double
Assuming your code is plain jane C code that should be enough to get it to work.
If the mex file includes file IO or some other Linux-specific feature, you will need to do more work. You can try compiling with MinGW or Cygwin. There’s a package on SourceForge called gnumex that will get that running. Or you could use macros to select the appropriate OS-specific functions.