On 10/5/2013 4:02 PM, Stephan T. Lavavej wrote:
[Edward Diener]
The problem from clang's perspective is that they must emulate this "feature" <g> to compile Boost type_traits. Their developers feel that Boost type_traits should not depend on this feature, ie. should not specify any VC++ calling conventions for varargs function or function template declarations.
I agree with clang's devs (because that's what VC's
does).
Thanks for the encouragement. I will quote you when I propose to John Maddock, the main Boost type_traits implementor, that Boost should so the same.
What I mean is that in VC++ the declarations are redundant, being the same template redeclared.
Right. So if you want to absorb all old-style varargs, you need only one overload/specialization.
It looks as if the overload specialization for C++ should specify __cdecl. If this is left out of a function specification, is not the default calling convention user-specified, with __cdecl being the default ? So if the end-user changes the default to something other than __cdecl is that considered the end-user's fault with VC++ ?
In this case clang either has to change to be like VC++
Oh, I thought clang was attempting to be VC-compatible here (like our copy of EDG for Intellisense does).
I believe that clang wants to be compatible enough to VC++ on Windows to be able to compile Windows header files, but still wants to follow the C++ standard as closely as possible. Of course it is a bit of a tightrope act because 3rd party libraries for Windows which test for VC++ using _MSC_VER and other VC++ macros which clang on Windows supports, may want to be able to use clang to compile the code also.
If clang is supposed to be VC-compatible, then they should treat varargs with calling conventions like VC does, and Boost should do what VC
does (i.e. one overload/specialization with no calling convention - or __cdecl would work, I think).
It seems as if __cdecl is better than no calling convention, because the end-user has the ability to change the default calling convention on VC++.
If clang wants to be different from VC, then Boost should do something different for clang and VC.
I do not work developing clang but I am just trying to compile Boost code with the clang toolset.