[gcc r12-7176] libstdc++: Fix directory iterator build for newlib

[Jonathan Wakely]

https://gcc.gnu.org/g:3d5f4f76e6db0895181ebca538748379bfe6058f

commit r12-7176-g3d5f4f76e6db0895181ebca538748379bfe6058f
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Feb 8 21:05:30 2022 +0000

    libstdc++: Fix directory iterator build for newlib
    
    When building for newlib HAVE_OPENAT and HAVE_UNLINKAT are (sometimes?)
    defined, but <fcntl.h> is only included when HAVE_DIRENT_H is defined.
    Since directory iterators are completely useless without <dirent.h>,
    just override the HAVE_OPENAT and HAVE_UNLINKAT detection when we don't
    have <dirent.h>.
    
    libstdc++-v3/ChangeLog:
    
            * src/filesystem/dir-common.h (_GLIBCXX_HAVE_DIRFD): Undefine
            when <dirent.h> is not available.
            (_GLIBCXX_HAVE_UNLINKAT):  Likewise.

Diff:
---
 libstdc++-v3/src/filesystem/dir-common.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libstdc++-v3/src/filesystem/dir-common.h b/libstdc++-v3/src/filesystem/dir-common.h
index 511b988f1c7..365fd527f4d 100644
--- 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