emacs-28 c2f94f32b5: Revert "Don’t assume openat"

[Eli Zaretskii]

branch: emacs-28
commit c2f94f32b5e8f57e2b4e723c9799cf0e5f5e5bcc
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Revert "Don’t assume openat"
    
    This reverts commit 3cccf0a9107d585173e527550bbc45253624ca2e.
    
    This is a change with far-reaching effects on MS-Windows at the least,
    where file-related APIs are shadowed to support transparent support
    for UTF-8 encoded file names.  Making such changes on a stable branch
    for the benefit of a proprietary platform with a 13-year old OS is a
    tail wagging the dog.  Please don't do that without discussing first.
---
 lib-src/emacsclient.c |  3 ++-
 src/sysdep.c          | 29 +++++++++++------------------
 2 files changed, 13 insertions(+), 19 deletions(-)

diff --git a/lib-src/emacsclient.c b/lib-src/emacsclient.c
index 217a38bc07..57a5eff3bf 100644
--- a/lib-src/emacsclient.c
+++ b/lib-src/emacsclient.c
@@ -1412,7 +1412,8 @@ local_sockname (int s, char sockname[socknamesize], int 
tmpdirlen,
   char *emacsdirend = sockname + tmpdirlen + suffixlen -
     strlen(server_name) - 1;
   *emacsdirend = '\0';
-  int dir = open (sockname, O_PATH | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+  int dir = openat (AT_FDCWD, sockname,
+                   O_PATH | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
   *emacsdirend = '/';
   if (dir < 0)
     return errno;
diff --git a/src/sysdep.c b/src/sysdep.c
index f6d139421a..72be25f661 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -2302,20 +2302,6 @@ emacs_fstatat (int dirfd, char const *filename, void 
*st, int flags)
   return r;
 }
 
-static int
-sys_openat (int dirfd, char const *file, int oflags, int mode)
-{
-#ifdef O_PATH
-  return openat (dirfd, file, oflags, mode);
-#else
-  /* On platforms without O_PATH, emacs_openat's callers arrange for
-     DIRFD to be AT_FDCWD, so it should be safe to just call 'open'.
-     This ports to old platforms like OS X 10.9 that lack openat.  */
-  eassert (dirfd == AT_FDCWD);
-  return open (file, oflags, mode);
-#endif
-}
-
 /* Assuming the directory DIRFD, open FILE for Emacs use,
    using open flags OFLAGS and mode MODE.
    Use binary I/O on systems that care about text vs binary I/O.
@@ -2331,7 +2317,7 @@ emacs_openat (int dirfd, char const *file, int oflags, 
int mode)
   if (! (oflags & O_TEXT))
     oflags |= O_BINARY;
   oflags |= O_CLOEXEC;
-  while ((fd = sys_openat (dirfd, file, oflags, mode)) < 0 && errno == EINTR)
+  while ((fd = openat (dirfd, file, oflags, mode)) < 0 && errno == EINTR)
     maybe_quit ();
   return fd;
 }
@@ -2344,19 +2330,26 @@ emacs_open (char const *file, int oflags, int mode)
 
 /* Same as above, but doesn't allow the user to quit.  */
 
-int
-emacs_open_noquit (char const *file, int oflags, int mode)
+static int
+emacs_openat_noquit (int dirfd, const char *file, int oflags,
+                     int mode)
 {
   int fd;
   if (! (oflags & O_TEXT))
     oflags |= O_BINARY;
   oflags |= O_CLOEXEC;
   do
-    fd = open (file, oflags, mode);
+    fd = openat (dirfd, file, oflags, mode);
   while (fd < 0 && errno == EINTR);
   return fd;
 }
 
+int
+emacs_open_noquit (char const *file, int oflags, int mode)
+{
+  return emacs_openat_noquit (AT_FDCWD, file, oflags, mode);
+}
+
 /* Open FILE as a stream for Emacs use, with mode MODE.
    Act like emacs_open with respect to threads, signals, and quits.  */