MSVC C++ 20 With Diagnostic Services

[ajorians]

The following information is odd anyway and as you'll see is easy to resolve on our side. Meaning I wasn't thinking any actions need to be done at all; but figured at least let you know about it.

First consider Microsoft has the ability to detect memory leaks with some Diagnostic Services via redefining the new operator:

With C++17 this isn't a problem as you can see with this online link: https://godbolt.org/z/nx35hhY9r

(note: Compiler Explorer doesn't install with MFC/ATL but those defines should give similar effect).

It builds. But if you change the setting to build as C++20 (or later) it fails to compile; here is an online link: https://godbolt.org/z/M3ba6r48h

I, myself, am using boost 1.81.0 where I am noticing this issue.

Hope that helps!

[pdimov]

The reason for the difference is that MSVC is using the old compiler frontend (/permissive) in C++17 mode and the new one in C++20 mode (/permissive-).

In "permissive" mode, syntax errors in templates that aren't used (such as the above shared_count constructor that takes an allocator) do not cause compilation to fail, but in "permissive-" mode, they do.

Since the code is already passing arguments to new, the macro that passes file/line causes a syntax error.