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

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

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.


> Regtested x86_64-pc-linux-gnu and no new failures detected.
>
> Fixes commit r12-7062-gebf61754647689 (libstdc++: Fix
> filesystem::remove_all races).
>
> libstdc++-v3/ChangeLog:
>
>         * src/filesystem/dir-common.h (_GLIBCXX_HAVE_FCNTL_H): Move the
>         check outside the HAVE_DIRENT_H check.
>
> Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>
> ---
>  libstdc++-v3/src/filesystem/dir-common.h | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/libstdc++-v3/src/filesystem/dir-common.h
> b/libstdc++-v3/src/filesystem/dir-common.h
> index 0b7665a3f70..cfce4fae9a4 100644
> --- a/libstdc++-v3/src/filesystem/dir-common.h
> +++ b/libstdc++-v3/src/filesystem/dir-common.h
> @@ -35,10 +35,11 @@
>  #  include <sys/types.h>
>  # endif
>  # include <dirent.h> // opendir, readdir, fdopendir, dirfd
> -# ifdef _GLIBCXX_HAVE_FCNTL_H
> -#  include <fcntl.h>  // open, openat, fcntl, AT_FDCWD, O_NOFOLLOW etc.
> -#  include <unistd.h> // close, unlinkat
> -# endif
> +#endif
> +
> +#ifdef _GLIBCXX_HAVE_FCNTL_H
> +# include <fcntl.h>  // open, openat, fcntl, AT_FDCWD, O_NOFOLLOW etc.
> +# include <unistd.h> // close, unlinkat
>  #endif
>
>  namespace std _GLIBCXX_VISIBILITY(default)
> --
> 2.34.1
>
>