[PATCH] Improve Windows toolchain support for non-standard environments.

[Aaron Ballman]

On Fri, Oct 17, 2014 at 4:38 PM, Zachary Turner <zturner at google.com> wrote:
>
>
> On Fri, Oct 17, 2014 at 1:27 PM, Aaron Ballman <aaron.ballman at gmail.com>
> wrote:
>>
>> On Fri, Oct 17, 2014 at 4:22 PM, Zachary Turner <zturner at google.com>
>> wrote:
>> >
>> >
>> > On Fri, Oct 17, 2014 at 12:48 PM, Aaron Ballman
>> > <aaron.ballman at gmail.com>
>> > wrote:
>> >>
>> >> On Fri, Oct 17, 2014 at 3:06 PM, Zachary Turner <zturner at google.com>
>> >> wrote:
>> >> > -
>> >> >  std::unique_ptr<Command> visualstudio::Compile::GetCommand(
>> >> >      Compilation &C, const JobAction &JA, const InputInfo &Output,
>> >> >      const InputInfoList &Inputs, const ArgList &Args,
>> >> > Index: lib/Driver/WindowsToolChain.cpp
>> >> > ===================================================================
>> >> > --- lib/Driver/WindowsToolChain.cpp
>> >> > +++ lib/Driver/WindowsToolChain.cpp
>> >> > @@ -77,61 +77,59 @@
>> >> >    return getArch() == llvm::Triple::x86_64;
>> >> >  }
>> >> >
>> >> > +#ifdef USE_WIN32
>> >> > +static bool readFullStringValue(HKEY hkey, const char *valueName,
>> >> > +                                std::string &value) {
>> >>
>> >> We should be preferring the W versions of these APIs instead of the A
>> >> versions, especially since this is being used to pull out file paths.
>> >
>> > How does this work, since ultimately all of clang uses non-wide
>> > character
>> > strings anyway.  I mean I know how to convert between the two, but I was
>> > under the impression that everything was just already broken because
>> > afaik
>> > we don't ever use W functions anywhere else.
>>
>> My understanding is that we use the W versions of the APIs and
>> immediately convert to UTF-8 to store internally. When we require
>> interaction in the other direction, we convert back to UTF-16. At
>> least, this is how we work with things like command line arguments and
>> files. As an example, see Process::GetArgumentVector.
>
>
> So llvm::sys::windows::UTF8ToUTF16 and its counterpart are not exposed in a
> public header.  Is there an accepted way to re-use them here, or do I need
> to duplicate the code in clang?

There's not an accepted way currently, but duplication isn't the answer either.

I think the registry code should be pulled down into an LLVM Support
interface that's available on Windows (since we're already using
USE_WIN32 within clang, I don't think the interface needs x-platform
stubs), and the conversion routines hoisted to a place where they can
be exposed for use within Support so that they can be used with the
registry code. Registry use shouldn't be overly widespread, so I think
the abstraction could be fairly simplistic.

~Aaron