swig 接口文件中未调用 C++ 析构函数

Question

I am creating an interface between c++ and python code.

I create a module called composition_api in a swig interface file. It has methods that I import into a python module as shown below.

/// SWIG Interface File.
%module composition_api
%{
    #include <include/mcm/compiler/compilation_unit.hpp>


    mv::CompilationUnit* getCompilationUnit(bool disableHardware)
    {
        auto unit = new mv::CompilationUnit("pySwigCU");
             return unit;
    }
}

I import this as library into a python script.

Python script

import composition_api as ca
compUnit = ca.getCompilationUnit(not enableHardware)

When the python script is finished running the CompilationUnit destructor is not being called in the C++ source code. Do I have to create a method in the interface file that calls delete unit ?

Answer 1

The C++ counterpart of compUnit is a pointer. When compUnit is garbage collected by Python, it simply garbage collects the pointer. It does not automatically call delete on the pointer.

You have couple of choices that I can think of.

1. Return an object to Python that is wrapper to the pointer. When the object gets garbage collected, its destructor will be called. Add the necessary code to delete the C++ object in the destructor of the wrapper.

2. Add an explicit function in the swig interface file to delete the object. Make sure to call the function in Python before the scope of the Python object ends.