[systemd-devel] [PATCH] check for name_to_handle_at declaration instead of its definition

[Michael Olbrich]

AC_CHECK_FUNCS may be successful, even though name_to_handle_at and
'struct file_handle'  are not available.

---

> This really looks like something to fix in libc. I mean, supporting
> libcs with and without this function makes sense, but supporting an
> (obviously broken/contradicting) glibc that exposes it as symbols but
> not in the headers (or vice versa) is another thing. I'd really prefer
> if this would be fixed in libc.

It's not quite that simple. I'm not sure how this works exactly, but the
definitions of the system calls are somehow generated from the kernel
headers that the glibc is built with. The declarations however are manually
added to the headers for each architecture.
I don't think it's reasonable to assume that the kernel headers and the
glibc are always exactly in sync.
And using AC_CHECK_DECLS instead is simple enough.

Regards,
Michael

 configure.ac         |    7 ++++---
 src/shared/missing.h |    2 +-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/configure.ac b/configure.ac
index 5d7d0c2..b543dbc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -172,11 +172,12 @@ CAP_LIBS="$LIBS"
 LIBS="$save_LIBS"
 AC_SUBST(CAP_LIBS)
 
-AC_CHECK_FUNCS([fanotify_init fanotify_mark name_to_handle_at])
+AC_CHECK_FUNCS([fanotify_init fanotify_mark])
 AC_CHECK_FUNCS([__secure_getenv secure_getenv])
-AC_CHECK_DECLS([gettid, pivot_root], [], [], [[#include <sys/types.h>
+AC_CHECK_DECLS([gettid, pivot_root, name_to_handle_at], [], [], [[#include <sys/types.h>
 #include <unistd.h>
-#include <sys/mount.h>]])
+#include <sys/mount.h>
+#include <fcntl.h>]])
 
 # This makes sure pkg.m4 is available.
 m4_pattern_forbid([^_?PKG_[A-Z_]+$],[*** pkg.m4 missing, please install pkg-config])
diff --git a/src/shared/missing.h b/src/shared/missing.h
index 14abe4e..de68327 100644
--- a/src/shared/missing.h
+++ b/src/shared/missing.h
@@ -218,7 +218,7 @@ static inline pid_t gettid(void) {
 #  endif
 #endif
 
-#ifndef HAVE_NAME_TO_HANDLE_AT
+#ifndef HAVE_DECL_NAME_TO_HANDLE_AT
 struct file_handle {
         unsigned int handle_bytes;
         int handle_type;
-- 
1.7.10.4