master 5a344d90c5: Port better to glibc 2.28+ renameat2

[Paul Eggert]

branch: master
commit 5a344d90c53d681ed98ab03ad3e218a3c6561108
Author: Paul Eggert <eggert@cs.ucla.edu>
Commit: Paul Eggert <eggert@cs.ucla.edu>

    Port better to glibc 2.28+ renameat2
    
    * configure.ac: Check for renameat2.
    * src/sysdep.c (renameat_noreplace): Prefer renameat2 (supplied by
    glibc 2.28 and later) to doing the syscall by hand.
---
 configure.ac | 1 +
 src/sysdep.c | 7 ++++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index 6e37d56d31..67c393e335 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4997,6 +4997,7 @@ pthread_sigmask strsignal setitimer \
 sendto recvfrom getsockname getifaddrs freeifaddrs \
 gai_strerror sync \
 getpwent endpwent getgrent endgrent \
+renameat2 \
 cfmakeraw cfsetspeed __executable_start log2 pthread_setname_np \
 pthread_set_name_np])
 LIBS=$OLD_LIBS
diff --git a/src/sysdep.c b/src/sysdep.c
index 736723bdf3..8402ffe308 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -2653,10 +2653,11 @@ emacs_perror (char const *message)
 int
 renameat_noreplace (int srcfd, char const *src, int dstfd, char const *dst)
 {
-#if defined SYS_renameat2 && defined RENAME_NOREPLACE
-  return syscall (SYS_renameat2, srcfd, src, dstfd, dst, RENAME_NOREPLACE);
-#elif defined CYGWIN && defined RENAME_NOREPLACE
+#if HAVE_RENAMEAT2 && defined RENAME_NOREPLACE
   return renameat2 (srcfd, src, dstfd, dst, RENAME_NOREPLACE);
+#elif defined SYS_renameat2 && defined RENAME_NOREPLACE
+  /* Linux kernel 3.15 (2014) or later, with glibc 2.27 (2018) or earlier.  */
+  return syscall (SYS_renameat2, srcfd, src, dstfd, dst, RENAME_NOREPLACE);
 #elif defined RENAME_EXCL
   return renameatx_np (srcfd, src, dstfd, dst, RENAME_EXCL);
 #else