Tuesday, 4 October 2016

Software Engineering : C++14 Factory Create Pattern for GCC

In my previous Software Engineering item, I covered a factory create pattern, to prevent programmers using my classes with their vanilla constructors, forcing them into using a smart pointer in the hope that they would never get a memory leak from using my classes (assuming my classes clean up cleanly internally).

This pattern can be seen here, but is specific to the Microsoft STL implementation of the Memory classes.

On Linux however, with GCC, you have to make a different class a friend, this is "__gnu_cxx::new_allocator", which like "_Ref_count_obj" is an implementation of a counter to references to the allocated class type.  It is also templated, and used exactly the same way as the Microsoft version.

Use it like this:

You can see my whole screen, with all the code here:

Click to Zoom in

On the left is the example code, on the right you see me invoke g++ with C++14 to compile and then run the example program.

The code clearly shows the private constructor, it's a trivial class, if any of that confuses you then this maybe too advanced an item for you to pick up on just yet, but do come back and learn this, as it's very useful when you've built up your C++ confidence.

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