[Issue 18928] extern(C++) bad codegen, wrong calling convention

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18928

--- Comment #4 from Manu <turkeyman at gmail.com> ---
If you look at the disassembly of userdatabase.d, you'll see that the virtual
function is not expecting the string in R8 where VC is putting it. It also
doesn't appear to return via the RVO pointer(?) in RDX.

The static call matches D's expectations.

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