r371027 - Revert r361885 "[Driver] Fix -working-directory issues"

[Hans Wennborg via cfe-commits]

Committed a fix in r373049, and I'll ask to have it merged for 9.0.1
as well. Sorry again for the breakage.

On Thu, Sep 26, 2019 at 7:09 PM Mikael Holmén
<mikael.holmen at ericsson.com> wrote:
>
> Hi,
>
> As Karl-Johan said I'll be out of office for a few days so please submit a fix if you can find the time.
>
> Thanks,
> Mikael
>
> Den 26 sep. 2019 15:39 skrev Hans Wennborg <hans at chromium.org>:
>
> On Thu, Sep 26, 2019 at 12:55 PM Mikael Holmén via cfe-commits
> <cfe-commits at lists.llvm.org> wrote:
> >
> > Hi Hans,
> >
> > I'm a bit suspicious against the part
> >
> >  > This also revertes the part of r369938 which checked that
> > -working-directory works.
> >
> > in this revert.
> >
> > You do:
> >
> >  > +  SmallString<128> Buf;
> >  > +  if (!llvm::sys::fs::current_path(Buf))
> >  > +    Buf = ".";
> >  > +  CDB << "{ \"directory\": \"" << escape(Buf) << "\"";
> >
> > But if I look at r369938 it seems like before r369938 it looked like
> >
> > -  SmallString<128> Buf;
> > -  if (llvm::sys::fs::current_path(Buf))
> > -    Buf = ".";
> > -  CDB << "{ \"directory\": \"" << escape(Buf) << "\"";
> >
> > Note the difference in the condition, where you do
> >
> >   if (!llvm::sys::fs::current_path(Buf))
> >
> > but before it was
> >
> >   if (llvm::sys::fs::current_path(Buf))
> >
> >
> > We noticed this since
> >
> >   clang -MJ test.json -O2 -nostdinc empty.c -S -o - && cat test.json
> >
> > started to behave differently after this revert. The "directory: " part
> > in the output suddenly became ".".
>
> You're right, it definitely looks like I messed up the revert :-(
> Looking at the code again, I was probably thrown off by the
> current_path returning false on success.
>
> Since you've been investigating, are you set up to land a fix with a
> test maybe? Otherwise I can do it, please let me know.
>
> Thanks,
> Hans