fts, savedir: avoid glibc 2.2 readdir ENOENT bug

This is mostly to document the bug.
If these old platforms were still common I suppose we should
change the readdir module to work around it.  However, I’m not
sure it’s worth the hassle at this point.
* doc/posix-functions/readdir.texi, doc/posix-functions/readdir_r.texi:
Document the bug.
* lib/fts.c (fts_build):
* lib/savedir.c (streamsavedir):
Work around it.

ChangeLog

@@ -1,3 +1,16 @@
+2025-01-13  Paul Eggert  <eggert@cs.ucla.edu>
+
+	fts, savedir: avoid glibc 2.2 readdir ENOENT bug
+	This is mostly to document the bug.
+	If these old platforms were still common I suppose we should
+	change the readdir module to work around it.  However, I’m not
+	sure it’s worth the hassle at this point.
+	* doc/posix-functions/readdir.texi, doc/posix-functions/readdir_r.texi:
+	Document the bug.
+	* lib/fts.c (fts_build):
+	* lib/savedir.c (streamsavedir):
+	Work around it.
+
 2025-01-13  Bruno Haible  <bruno@clisp.org>
 
 	stdlib-h: Define WCOREDUMP, as required by POSIX:2024.

doc/posix-functions/readdir.texi

@@ -30,4 +30,9 @@ formerly attempted to cater to these older systems, this caused
 misbehavior on standard systems and so Gnulib does not attempt to
 cater to them any more.  If you know of any problems caused by this,
 please send a bug report.
+@item
+When reading a directory that has been removed,
+this function sets @code{errno} to @code{ENOENT}
+instead of leaving @code{errno} alone to indicate EOF:
+glibc 2.2.5.
 @end itemize

doc/posix-functions/readdir_r.texi

@@ -28,4 +28,9 @@ Portability problems not fixed by Gnulib:
 @item
 This function is missing on some platforms:
 Minix 3.1.8, mingw, MSVC 14.
+@item
+When reading a directory that has been removed,
+this function sets @code{errno} to @code{ENOENT}
+instead of leaving @code{errno} alone to indicate EOF:
+glibc 2.2.5.
 @end itemize

lib/fts.c

@@ -1443,6 +1443,13 @@ fts_build (register FTS *sp, int type)
                 __set_errno (0);
                 struct dirent *dp = readdir(cur->fts_dirp);
                 if (dp == NULL) {
+                        /* Some readdir()s do not absorb ENOENT (dir
+                           deleted but open).  This bug was fixed in
+                           glibc 2.3 (2002).  */
+#if ! (2 < __GLIBC__ + (3 <= __GLIBC_MINOR__))
+                        if (errno == ENOENT)
+                          errno = 0;
+#endif
                         if (errno) {
                                 cur->fts_errno = errno;
                                 /* If we've not read any items yet, treat

lib/savedir.c

@@ -123,7 +123,15 @@ streamsavedir (DIR *dirp, enum savedir_option option)
       errno = 0;
       dp = readdir (dirp);
       if (! dp)
-        break;
+        {
+          /* Some readdir()s do not absorb ENOENT (dir deleted but open).
+             This bug was fixed in glibc 2.3 (2002).  */
+#if ! (2 < __GLIBC__ + (3 <= __GLIBC_MINOR__))
+          if (errno == ENOENT)
+            errno = 0;
+#endif
+          break;
+        }
 
       /* Skip "", ".", and "..".  "" is returned by at least one buggy
          implementation: Solaris 2.4 readdir on NFS file systems.  */