Even minor point releases of Visual Studio can cause significant behavior changes and ABI breakages. The full range of defaults that changes inside Visual Studio for a major release may be more than can be accommodated with user options. Switching the Visual Studio “platform toolset” version may be of help.
In Visual Studio, click Project → Properties → Platform Toolset. If the desired toolset is not present, use Visual Studio Installer to obtain it.
/permissive- flag is default in VS2019, but just turning that flag off may not be enough to compile projects from older MSVC versions.
/permissive- flag is under Project → Properties → C/C++ →; Language → conformance mode.