From 50126f2049a03d2910412572c98bafbc26f3db31 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Wed, 24 Jul 2019 11:28:48 -0700
Subject: [PATCH] Port double-slash test to z/OS

* admin/merge-gnulib (GNULIB_MODULES): Add double-slash-root.
Emacs was already using this Gnulib module indirectly, so this
is merely noting that there is now a direct dependency.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* src/fileio.c (search_embedded_absfilename):
Use DOUBLE_SLASH_IS_DISTINCT_ROOT instead of (WINDOWSNT || CYGWIN).
Simplify.
---
 admin/merge-gnulib |  2 +-
 lib/gnulib.mk.in   |  1 +
 m4/gnulib-comp.m4  |  2 ++
 src/fileio.c       | 22 ++++++++++------------
 4 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/admin/merge-gnulib b/admin/merge-gnulib
index 42e9c0c8645..50b0c762a8f 100755
--- a/admin/merge-gnulib
+++ b/admin/merge-gnulib
@@ -31,7 +31,7 @@ GNULIB_MODULES='
   careadlinkat close-stream copy-file-range
   count-leading-zeros count-one-bits count-trailing-zeros
   crypto/md5-buffer crypto/sha1-buffer crypto/sha256-buffer crypto/sha512-buffer
-  d-type diffseq dosname dtoastr dtotimespec dup2
+  d-type diffseq dosname double-slash-root dtoastr dtotimespec dup2
   environ execinfo explicit_bzero faccessat
   fcntl fcntl-h fdopendir
   filemode filevercmp flexmember fpieee fstatat fsusage fsync
diff --git a/lib/gnulib.mk.in b/lib/gnulib.mk.in
index 85fdbd2df6f..79580e931ab 100644
--- a/lib/gnulib.mk.in
+++ b/lib/gnulib.mk.in
@@ -86,6 +86,7 @@
 #  d-type \
 #  diffseq \
 #  dosname \
+#  double-slash-root \
 #  dtoastr \
 #  dtotimespec \
 #  dup2 \
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index d6b2009123d..77563edc84d 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -70,6 +70,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module dirent:
   # Code from module dirfd:
   # Code from module dosname:
+  # Code from module double-slash-root:
   # Code from module dtoastr:
   # Code from module dtotimespec:
   # Code from module dup2:
@@ -227,6 +228,7 @@ AC_DEFUN([gl_INIT],
   gl_SHA512
   gl_CHECK_TYPE_STRUCT_DIRENT_D_TYPE
   gl_DIRENT_H
+  gl_DOUBLE_SLASH_ROOT
   gl_FUNC_DUP2
   if test $HAVE_DUP2 = 0 || test $REPLACE_DUP2 = 1; then
     AC_LIBOBJ([dup2])
diff --git a/src/fileio.c b/src/fileio.c
index 4c7625cad4a..e4269b96a37 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -1778,20 +1778,18 @@ get_homedir (void)
 static char *
 search_embedded_absfilename (char *nm, char *endp)
 {
-  char *p, *s;
-
-  for (p = nm + 1; p < endp; p++)
+  char *p = nm + 1;
+#ifdef DOUBLE_SLASH_IS_DISTINCT_ROOT
+  p += (IS_DIRECTORY_SEP (p[-1]) && IS_DIRECTORY_SEP (p[0])
+	&& !IS_DIRECTORY_SEP (p[1]));
+#endif
+  for (; p < endp; p++)
     {
-      if (IS_DIRECTORY_SEP (p[-1])
-	  && file_name_absolute_p (p)
-#if defined (WINDOWSNT) || defined (CYGWIN)
-	  /* // at start of file name is meaningful in Apollo,
-	     WindowsNT and Cygwin systems.  */
-	  && !(IS_DIRECTORY_SEP (p[0]) && p - 1 == nm)
-#endif /* not (WINDOWSNT || CYGWIN) */
-	  )
+      if (IS_DIRECTORY_SEP (p[-1]) && file_name_absolute_p (p))
 	{
-	  for (s = p; *s && !IS_DIRECTORY_SEP (*s); s++);
+	  char *s;
+	  for (s = p; *s && !IS_DIRECTORY_SEP (*s); s++)
+	    continue;
 	  if (p[0] == '~' && s > p + 1)	/* We've got "/~something/".  */
 	    {
 	      USE_SAFE_ALLOCA;
-- 
2.39.2