How to restore auto_ptr in Visual Studio C++17

Question

This blog page mentions that Visual Studio removes some std features:

https://blogs.msdn.microsoft.com/vcblog/2017/12/08/c17-feature-removals-and-deprecations/

I have a project that consumes some C++ libraries that now use C++17 features. The project also consumes a third party library websocketpp (https://github.com/zaphoyd/websocketpp) that still uses some now removed features. eg auto_ptr and binary_function. I'm getting compiler errors that they are not a member of 'std'.

The blog above mentions that removed features can be restored using a fine grain control. I'm thinking I could use that to get this project to compile for now. Longer term I will see about upgrading websocketpp to C++17 or replacing it with something else.

But, what is the magic to restore features? Is there something I need to #define? If so, what?

Answer 1

In VS2017 v15.5 it is conditionally excluded, based on the project's /std:c++17 setting. You can force it to be included by forcing the underlying macro value. Two basic ways to do this:

1. Project > Properties > C/C++ > Preprocessor > Preprocessor Definitions and add _HAS_AUTO_PTR_ETC=1. Do so for all configurations and platforms.
2. If you use a precompiled header then you probably favor defining the macro there. Before any #includes, insert #define _HAS_AUTO_PTR_ETC 1.

Beware of the "ETC", you'll also slurp the deprecated random_shuffle() and unary_function<>. Predicting the future is difficult, but this is probably going to work for a while to come.