rtems6.0 has fdopendir, and fcntl.h defines AT_FDCWD and declares
openat, but there's no openat in libc. Adjust dir-common.h to not
assume ::openat just because of AT_FDCWD.
Regstrapped on x86_64-linux-gnu (detects and still uses openat), also
tested with a cross to aarch64-rtems6 (detects openat's absence and
refrains from using it). Ok to install?
PS: This is the last patch in my rtems6.0 patchset, and the only patch
for the filesystem-related patchset that was written specifically for a
mainline gcc. gcc-11 did not attempt to use openat. This patch enabled
filesystem tests to link when testing mainline on aarch64-rtems6.0.
Alas, several filesystem tests still failed with it, in ways that AFAICT
are not related with the use of openat, or with the other patches I've
posted. However, I'm not able to look into the remaining failures right
now.
for libstdc++-v3/ChangeLog
* acinclude.m4 (GLIBCXX_CHECK_FILESYSTEM_DEPS): Check for
openat.
* aclocal.m4, configure, config.h.in: Rebuilt.
* src/filesystem/dir-common.h (openat): Use ::openat if
_GLIBCXX_HAVE_OPENAT.
---
libstdc++-v3/acinclude.m4 | 12 +++++++
libstdc++-v3/config.h.in | 3 ++
libstdc++-v3/configure | 55 ++++++++++++++++++++++++++++++
libstdc++-v3/src/filesystem/dir-common.h | 2 +
4 files changed, 71 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 138bd58d86cb9..e3cc3a8e867d3 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -4772,6 +4772,18 @@ dnl
if test $glibcxx_cv_dirfd = yes; then
AC_DEFINE(HAVE_DIRFD, 1, [Define if dirfd is available in <dirent.h>.])
fi
+dnl
+ AC_CACHE_CHECK([for openat],
+ glibcxx_cv_openat, [dnl
+ GCC_TRY_COMPILE_OR_LINK(
+ [#include <fcntl.h>],
+ [int fd = ::openat(AT_FDCWD, "", 0);],
+ [glibcxx_cv_openat=yes],
+ [glibcxx_cv_openat=no])
+ ])
+ if test $glibcxx_cv_openat = yes; then
+ AC_DEFINE(HAVE_OPENAT, 1, [Define if openat is available in <fcntl.h>.])
+ fi
dnl
AC_CACHE_CHECK([for unlinkat],
glibcxx_cv_unlinkat, [dnl
diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in
index f30a8c51c458c..2a3972eef5412 100644
--- a/libstdc++-v3/config.h.in
+++ b/libstdc++-v3/config.h.in
@@ -292,6 +292,9 @@
/* Define if <math.h> defines obsolete isnan function. */
#undef HAVE_OBSOLETE_ISNAN
+/* Define if openat is available in <fcntl.h>. */
+#undef HAVE_OPENAT
+
/* Define if poll is available in <poll.h>. */
#undef HAVE_POLL
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 9b94fd71e4248..eac6039212168 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -77177,6 +77177,61 @@ $as_echo "$glibcxx_cv_dirfd" >&6; }
$as_echo "#define HAVE_DIRFD 1" >>confdefs.h
+ fi
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking for openat" >&5
+$as_echo_n "checking for openat... " >&6; }
+if ${glibcxx_cv_openat+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ if test x$gcc_no_link = xyes; then
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+#include <fcntl.h>
+int
+main ()
+{
+int fd = ::openat(AT_FDCWD, "", 0);
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+ glibcxx_cv_openat=yes
+else
+ glibcxx_cv_openat=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+else
+ if test x$gcc_no_link = xyes; then
+ as_fn_error $? "Link tests are not allowed after GCC_NO_EXECUTABLES."
"$LINENO" 5
+fi
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+#include <fcntl.h>
+int
+main ()
+{
+int fd = ::openat(AT_FDCWD, "", 0);
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+ glibcxx_cv_openat=yes
+else
+ glibcxx_cv_openat=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+ conftest$ac_exeext conftest.$ac_ext
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_openat" >&5
+$as_echo "$glibcxx_cv_openat" >&6; }
+ if test $glibcxx_cv_openat = yes; then
+
+$as_echo "#define HAVE_OPENAT 1" >>confdefs.h
+
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for unlinkat" >&5
$as_echo_n "checking for unlinkat... " >&6; }
diff --git a/libstdc++-v3/src/filesystem/dir-common.h
b/libstdc++-v3/src/filesystem/dir-common.h
index 365fd527f4d68..669780ea23fe5 100644
--- a/libstdc++-v3/src/filesystem/dir-common.h
+++ b/libstdc++-v3/src/filesystem/dir-common.h
@@ -199,7 +199,7 @@ struct _Dir_base
#endif
-#ifdef AT_FDCWD
+#if _GLIBCXX_HAVE_OPENAT && defined AT_FDCWD
fd = ::openat(fd, pathname, flags);
#else
// If we cannot use openat, there's no benefit to using posix::open unless
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts. Ask me about <https://stallmansupport.org>
