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Will memory leaks happen when the MEX file contains new & delete or STL containers (C++)?

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Eli4ph
Eli4ph on 5 Sep 2017
Edited: José-Luis on 5 Sep 2017
Memory Management in documentation says that mxCalloc and mxFree, instead of calloc and free in standard C library, should be used to manage memory.
However, it is sometimes unavoidable to use new & delete when using C++ classes in MEX file, as well as the automatic memory management of STL containers when using them.
Here comes the question. If the user sometimes interrupts the MEX file execution using Ctrl+C, and if the MEX file contains new & delete or STL containers, will memory leaks happen? If so, how to avoid memory leaks (with least extra work)?

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Philip Borghesani
Philip Borghesani on 5 Sep 2017
SIGINT does not apply here. MATLAB will handle SIGINT and will throw a synchronous c++ exception when it is safe to do so. Under no circumstances should a MEX file attempt to install a signal handler doing so will interfere with MATLAB's signal handler and cause never ending grief.

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Accepted Answer

Philip Borghesani
Philip Borghesani on 5 Sep 2017
The short answer is: Put anything allocated with a standard allocator into a smart pointer (unique_ptr, shared_ptr,...) and never put a MATLAB allocated object (mxMalloc, mxCreate...) into a smart pointer or attempt to free one on object destruction and you will be fine.
Most of the documentation/API is written from the perspective of C and FORTRAN mex programming and has not been updated for C++ yet. If you are using a supported C++ compiler (I am not completely sure about minGW on Windows) then the normal C++ exception mechanism is used and destructors are run when ctrl-c is used in a mex file.

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Eli4ph
Eli4ph on 5 Sep 2017
Great! So the extra work to avoid memory leaks is putting them into smart pointers? Also, forgive my bad understanding, what does 'attempt to free one on object destruction' mean? (I am not completely sure.)
José-Luis
José-Luis on 5 Sep 2017
Great. Learned something today.
So whatever cleanup is needed should be explicitly handled in the destructors?
And if memory is left dangling it will live in limbo until you exit Matlab?

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