C++ API and allocators (memory management)

Question

Marie 2023-7-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1994693-c-api-and-allocators-memory-management

回答： Shreeya 2023-8-25

I have a mex function that I am updating to use the C++ API so that I can create string arrays as opposed to cell arrays of characters. I use standard library functions (e.g. std::regex_iterator) that rely on memory allocation routines within the call. When I used the C API, I had a custom allocator template class (mex_allocator<T>) that let the standard libraries use Matlab's memory allocation (e.g., MxMalloc), similar in vain to @hokiedsp's allocator class used in matlab-mexutils. I then bound the standard library functions such that the custom allocator class was used, e.g.:

// Use custom Matlab allocator in these STL functions
namespace mxalloc {
  using string = std::basic_string<char, std::char_traits<char>,
				   mex_allocator<char>>;
  using smatch = 
    std::match_results<mxalloc::string::const_iterator,
		       mex_allocator<std::string::const_iterator>>;
  ... other routines
}

The C++ API does not list mxMalloc and mxFree as functions and indicates that the C and C++ interfaces should not be mixed. Are there an alternative memory allocation routines that I can use in a similar manner? In the past (circa R2017b?), I have had issues with letting the STL use the native memory allocation.

Thanks - Marie

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Answer 1

Shreeya 2023-8-25

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https://ww2.mathworks.cn/matlabcentral/answers/1994693-c-api-and-allocators-memory-management#answer_1293477

Hello Marie

I understand you want to create string arrays as opposed to cell arrays of characters which requires a custom memory allocator template for C++, similar to C.

Find the wrapper around mxMalloc and mxFree API’s for C++ in the file exchange below for an alternate memory allocation routine.

C++ MEX Development Utilities - File Exchange - MATLAB Central (mathworks.com)

Hope this helps.