[cfe-dev] Handling legacy VC++ deficiencies

[Aaron Ballman]

On Tue, Aug 28, 2012 at 9:35 AM, David Robins <llvm at davidrobins.net> wrote:
> I remember seeing in another email that Clang does not want to be "bug
> for bug compatible" with MSVC (and in yet another support for the bug
> where VS 2005 eats a comma in varargs macros); what's the best way to
> support compiling legacy code? Is it to be entirely unsupported? Can a
> plugin do it? Or will changes restricted to particular Microsoft compiler
> emulation (-fmsc-ver) be accepted?

I think it depends heavily on the bug, how much code is affected by
it, and how trivial the changes to the source base will be.  Since
this is in code generated by MSVC in a relatively "recent" version of
the compiler and is likely to affect a fair number of people, I think
it's reasonable to support the change in -fms-compatibility mode
assuming it isn't overly onerous to implement and maintain.  If
there's documentation on MSDN that describes the behavior, it makes
the case stronger for supporting it.

Just my 2 cents though.  :-)

~Aaron