Advanced Topics :: Creating C Language MEX-Files (External Interfaces)

External Interfaces

Advanced Topics

These sections cover advanced features of MEX-files that you can use when your applications require sophisticated MEX-files:

Help Files

Because the MATLAB interpreter chooses the MEX-file when both an M-file and a MEX-file with the same name are encountered in the same directory, it is possible to use M-files for documenting the behavior of your MEX-files. The MATLAB help command will automatically find and display the appropriate M-file when help is requested and the interpreter will find and execute the corresponding MEX-file when the function is invoked.

Linking Multiple Files

It is possible to combine several object files and to use object file libraries when building MEX-files. To do so, simply list the additional files with their full extension, separated by spaces. For example, on the PC

mex circle.c square.obj rectangle.c shapes.lib

is a legal command that operates on the .c, .obj, and .lib files to create a MEX-file called circle.dll, where dll is the extension corresponding to the MEX-file type on the PC. The name of the resulting MEX-file is taken from the first file in the list.

You may find it useful to use a software development tool like MAKE to manage MEX-file projects involving multiple source files. Simply create a MAKEFILE that contains a rule for producing object files from each of your source files and then invoke mex to combine your object files into a MEX-file. This way you can ensure that your source files are recompiled only when necessary.

Note On UNIX, you must use the -cxx switch to the mex script if you are linking C++ objects.

Workspace for MEX-File Functions

Unlike M-file functions, MEX-file functions do not have their own variable workspace. MEX-file functions operate in the caller's workspace.

mexEvalString evaluates the string in the caller's workspace. In addition, you can use the mexGetVariable and mexPutVariable routines to get and put variables into the caller's workspace.

Calling Functions from C MEX-Files Memory Management