Re: [PATCH] libstdc++: Decouple HAVE_FCNTL_H from HAVE_DIRENT_H check

[Jonathan Wakely <jwakely.gcc@gmail.com>]

On Tue, 8 Feb 2022 at 21:02, Dimitar Dimitrov <dimitar@dinux.eu> wrote:

> On Mon, Feb 07, 2022 at 09:05:45PM +0000, Jonathan Wakely wrote:
> > On Mon, 7 Feb 2022 at 21:01, Jonathan Wakely <jwakely.gcc@gmail.com>
> wrote:
> >
> > >
> > >
> > > On Mon, 7 Feb 2022 at 20:12, Dimitar Dimitrov <dimitar@dinux.eu>
> wrote:
> > >
> > >> On PRU target with newlib, we have the following combination in
> config.h:
> > >>   /* #undef HAVE_DIRENT_H */
> > >>   #define HAVE_FCNTL_H 1
> > >>   #define HAVE_UNLINKAT 1
> > >>
> > >> In newlib, targets which do not define dirent.h, get a build error
> when
> > >> including <dirent.h>:
> > >>
> > >>
> https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=newlib/libc/include/sys/dirent.h;hb=HEAD
> > >>
> > >> While fs_dir.cc correctly checks for HAVE_FCNTL_H, dir-common.h
> doesn't,
> > >> and instead uses HAVE_DIRENT_H. This results in unlinkat() function
> call
> > >> in fs_dir.cc without the needed <fcntl.h> include in dir-common.h.
> Thus
> > >> a build failure:
> > >>   .../gcc/libstdc++-v3/src/c++17/fs_dir.cc:151:11: error: ‘::unlinkat’
> > >> has not been declared; did you mean ‘unlink’?
> > >>
> > >> Fix by encapsulating <fcntl.h> include with the correct check.
> > >>
> > >
> > > But there's no point doing anything in that file if we don't have
> > > <dirent.h>, the whole thing is unusable. There's no point making the
> > > members using unlinkat compile if you can't ever construct the type.
> > >
> > > So I think we want a different fix.
> > >
> >
> >
> > Maybe something like:
> >
> > --- a/libstdc++-v3/src/filesystem/dir-common.h
> > +++ b/libstdc++-v3/src/filesystem/dir-common.h
> > @@ -70,6 +70,8 @@ struct DIR { };
> > inline DIR* opendir(const char*) { return nullptr; }
> > inline dirent* readdir(DIR*) { return nullptr; }
> > inline int closedir(DIR*) { return -1; }
> > +#undef _GLIBCXX_HAVE_DIRFD
> > +#undef _GLIBCXX_HAVE_UNLINKAT
> > #endif
> > } // namespace __gnu_posix
> Yes, this fixes the PRU target, and does not regress
> x86_64-pc-linux-gnu.
>

Thanks for checking it. I'm just testing it myself on powerpc64le-linux-gnu
and will push when it finishes.