After recently updating the Qt Visual Studio Tools extension to version 2.7.2, the compilation step of all of our Qt projects failed with the message #error: "Qt requires a C++17 compiler, and a suitable value for _cplusplus. On MSVC, you must pass the /Zc:cplusplus option to the compiler.". Only the moc* files generated by Qt are affected. Other files in the same projects compile without issue.

Inspecting the command line output for these projects show that this flag is indeed no longer present for the affected files. We set this flag through some visual studio .props files, so that all of our projects inherit it. This has not caused us any issues, until now. 

Reverting the extension back to version 2.7.1 solves our problems, for now.