[llvm] r234343 - Enable W4 warnings by default for MSVC builds

[Yaron Keren]

This LGTM, with #ifdef _MSC_VER macro of course, maybe in Compiler.h ?

I wouldn't mind disabling the warning completely either, I don't find it
helpful.


2015-04-16 18:12 GMT+03:00 Aaron Ballman <aaron at aaronballman.com>:

> Since AlignOf is part of our support headers, I would slightly prefer
> if we could fix it there. As an experiment, I put in the proper
> #pragma incantation around the declaration of AlignmentCalcImpl<T> in
> AlignOf.h, and it resolved *all* of the warnings.
>
> #pragma warning(push)
> #pragma warning(disable : 4324)
> template <typename T>
> struct AlignmentCalcImpl {
>   char x;
>   T t;
> private:
>   AlignmentCalcImpl() {} // Never instantiate.
> };
> #pragma warning(pop)
>
>
> While the #pragma dance is ugly (and would need to be abstracted away
> via macros), it may be worth it since this is a support header (and we
> cannot fix the padding issue because that's the whole point to that
> structure). How do others feel?
>
> ~Aaron
>
> On Thu, Apr 16, 2015 at 10:49 AM, Yaron Keren <yaron.keren at gmail.com>
> wrote:
> > /W3 was probably cached from the previous build.
> >
> > So should we disable C4324 or fix (how?) the AlignOf?
> >
> >
> > 2015-04-16 17:34 GMT+03:00 Aaron Ballman <aaron at aaronballman.com>:
> >>
> >> It seems that in order to trigger this, you have to have done a clean
> >> cmake build, as I am now seeing the same warnings you are.
> >>
> >> ~Aaron
> >>
> >> On Thu, Apr 16, 2015 at 10:16 AM, Aaron Ballman <aaron at aaronballman.com
> >
> >> wrote:
> >> > On Thu, Apr 16, 2015 at 10:03 AM, Yaron Keren <yaron.keren at gmail.com>
> >> > wrote:
> >> >> It is same in the IDE and command line, Release or Debug
> (unthreaded),
> >> >> 32
> >> >> bit.
> >> >> The warning is:
> >> >>
> >> >>   PPMacroExpansion.cpp
> >> >> c:\llvm\include\llvm/Support/AlignOf.h(25): warning C4324:
> >> >> 'llvm::AlignmentCalcImpl<T>' : structure was padded due to
> >> >> __declspec(align())
> [c:\llvm\msvc\tools\clang\lib\Lex\clangLex.vcxproj]
> >> >>           with
> >> >>           [
> >> >>               T=clang::SrcMgr::ContentCache
> >> >>           ] (c:\llvm\tools\clang\lib\Lex\PPCaching.cpp)
> >> >>           c:\llvm\include\llvm/Support/AlignOf.h(40) : see reference
> to
> >> >> class template instantiation 'llvm::AlignmentC
> >> >>   alcImpl<T>' being compiled
> >> >>           with
> >> >>           [
> >> >>               T=clang::SrcMgr::ContentCache
> >> >>           ]
> >> >>
>  c:\llvm\tools\clang\include\clang/Basic/SourceManager.h(225)
> >> >> : see
> >> >> reference to class template instantiation
> >> >>    'llvm::AlignOf<clang::SrcMgr::ContentCache>' being compiled
> >> >>
> >> >> referring to SourceManager.h(225):
> >> >>
> >> >>   static_assert(llvm::AlignOf<ContentCache>::Alignment >= 8,
> >> >>                 "ContentCache must be 8-byte aligned.");
> >> >>
> >> >> And appears whenever SourceManager.h is included, a lot.
> >> >>
> >> >> The compiler is Microsoft Visual Studio Ultimate 2013,  Version
> >> >> 12.0.31101.00 Update 4.
> >> >>
> >> >> I'll try threaded build now.
> >> >
> >> > I will do a clean rebuild from scratch; I wonder if the reason I'm not
> >> > seeing anything is because of some caching somewhere. Thank you!
> >> >
> >> > ~Aaron
> >
> >
>
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