filemode: Remove Cray support

[Bruno Haible]

The AC_STRUCT_ST_DM_MODE macro caught my eye: its name starts with AC_ but
it is not part of Autoconf.

Looking deeper, I find that a web search for
  "checking for st_dm_mode in struct stat... yes"
finds 0 hits. That's because st_dm_mode existed only on Cray [1]. We missed
it when removing Cray support in July [2][3].

[1] http://owentrek.com/rkowen/howto/cugc90dmf/article/indexM.html
[2] https://lists.gnu.org/archive/html/bug-gnulib/2020-07/msg00139.html
[3] https://lists.gnu.org/archive/html/bug-gnulib/2020-07/msg00179.html


2020-12-20  Bruno Haible  <bruno@clisp.org>

        filemode: Remove Cray support.
        * lib/filemode.c (IS_MIGRATED_FILE): Remove macro.
        (filemodestring): Don't produce an 'M' type.
        * m4/filemode.m4 (gl_FILEMODE): Don't invoke AC_STRUCT_ST_DM_MODE.
        * m4/st_dm_mode.m4: Remove file.
        * modules/filemode (Files): Remove it.

diff --git a/lib/filemode.c b/lib/filemode.c
index e1b0690..15e3551 100644
--- a/lib/filemode.c
+++ b/lib/filemode.c
@@ -20,17 +20,6 @@
 
 #include "filemode.h"
 
-/* The following is for Cray DMF (Data Migration Facility), which is a
-   HSM file system.  A migrated file has a 'st_dm_mode' that is
-   different from the normal 'st_mode', so any tests for migrated
-   files should use the former.  */
-#if HAVE_ST_DM_MODE
-# define IS_MIGRATED_FILE(statp) \
-    (S_ISOFD (statp->st_dm_mode) || S_ISOFL (statp->st_dm_mode))
-#else
-# define IS_MIGRATED_FILE(statp) 0
-#endif
-
 #if ! HAVE_DECL_STRMODE
 
 /* Return a character indicating the type of file described by
@@ -126,7 +115,6 @@ strmode (mode_t mode, char *str)
         for files whose type cannot be determined solely from st_mode:
 
             'F' semaphore
-            'M' migrated file (Cray DMF)
             'Q' message queue
             'S' shared memory object
             'T' typed memory object
@@ -169,8 +157,6 @@ filemodestring (struct stat const *statp, char *str)
 
   if (S_TYPEISSEM (statp))
     str[0] = 'F';
-  else if (IS_MIGRATED_FILE (statp))
-    str[0] = 'M';
   else if (S_TYPEISMQ (statp))
     str[0] = 'Q';
   else if (S_TYPEISSHM (statp))
diff --git a/m4/filemode.m4 b/m4/filemode.m4
index 5aaaa1a..8bbfcdb 100644
--- a/m4/filemode.m4
+++ b/m4/filemode.m4
@@ -1,4 +1,4 @@
-# filemode.m4 serial 8
+# filemode.m4 serial 9
 dnl Copyright (C) 2002, 2005-2006, 2009-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,6 +6,5 @@ dnl with or without modifications, as long as this notice is 
preserved.
 
 AC_DEFUN([gl_FILEMODE],
 [
-  AC_REQUIRE([AC_STRUCT_ST_DM_MODE])
   AC_CHECK_DECLS_ONCE([strmode])
 ])
diff --git a/m4/st_dm_mode.m4 b/m4/st_dm_mode.m4
deleted file mode 100644
index 5dad161..0000000
--- a/m4/st_dm_mode.m4
+++ /dev/null
@@ -1,23 +0,0 @@
-# serial 6
-
-# Copyright (C) 1998-1999, 2001, 2009-2020 Free Software Foundation, Inc.
-# This file is free software; the Free Software Foundation
-# gives unlimited permission to copy and/or distribute it,
-# with or without modifications, as long as this notice is preserved.
-
-# Define HAVE_ST_DM_MODE if struct stat has an st_dm_mode member.
-
-AC_DEFUN([AC_STRUCT_ST_DM_MODE],
- [AC_CACHE_CHECK([for st_dm_mode in struct stat], [ac_cv_struct_st_dm_mode],
-   [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
-#include <sys/types.h>
-#include <sys/stat.h>]], [[struct stat s; s.st_dm_mode;]])],
-     [ac_cv_struct_st_dm_mode=yes],
-     [ac_cv_struct_st_dm_mode=no])])
-
-  if test $ac_cv_struct_st_dm_mode = yes; then
-    AC_DEFINE([HAVE_ST_DM_MODE], [1],
-              [Define if struct stat has an st_dm_mode member.])
-  fi
- ]
-)
diff --git a/modules/filemode b/modules/filemode
index be442ba..95d3e0f 100644
--- a/modules/filemode
+++ b/modules/filemode
@@ -6,7 +6,6 @@ Files:
 lib/filemode.h
 lib/filemode.c
 m4/filemode.m4
-m4/st_dm_mode.m4
 
 Depends-on:
 sys_stat