---
lib/sys_stat.in.h | 26 +++++++++++++++++---------
1 file changed, 17 insertions(+), 9 deletions(-)
diff --git a/lib/sys_stat.in.h b/lib/sys_stat.in.h
index 567dffa620..0c9f6b761b 100644
--- a/lib/sys_stat.in.h
+++ b/lib/sys_stat.in.h
@@ -255,7 +255,9 @@ struct stat
# endif
#endif
-#ifndef S_ISMPB /* V7 */
+/* These multiplex file types were in Version 7 Unix, last supported
+ in the early 1980s. Perhaps remove them here? */
+#ifndef S_ISMPB
# ifdef S_IFMPB
# define S_ISMPB(m) (((m) & S_IFMT) == S_IFMPB)
# define S_ISMPC(m) (((m) & S_IFMT) == S_IFMPC)
@@ -265,11 +267,13 @@ struct stat
# endif
#endif
-#ifndef S_ISMPX /* AIX */
+/* This multiplex file type is in AIX; although useless these days,
+ it is still in AIX 7.3 <sys/stat.h>. */
+#ifndef S_ISMPX
# define S_ISMPX(m) 0
#endif
-#ifndef S_ISNAM /* Xenix */
+#ifndef S_ISNAM /* QNX */
# ifdef S_IFNAM
# define S_ISNAM(m) (((m) & S_IFMT) == S_IFNAM)
# else
@@ -277,7 +281,9 @@ struct stat
# endif
#endif
-#ifndef S_ISNWK /* HP/UX */
+/* This network file type was in HP-UX 9 and 10, last supported in the
+ early 2000s. Perhaps remove S_ISNWK here? */
+#ifndef S_ISNWK
# ifdef S_IFNWK
# define S_ISNWK(m) (((m) & S_IFMT) == S_IFNWK)
# else
@@ -331,22 +337,24 @@ struct stat
# endif
#endif
-/* high performance ("contiguous data") */
+/* This contiguous data file type was in RTU, last supported in the
+ early 2000s. Perhaps remove it here? */
#ifndef S_ISCTG
# define S_ISCTG(p) 0
#endif
-/* Cray DMF (data migration facility): off line, with data */
+/* Cray DMF (data migration facility): offline with and without data.
+ These file types were in classic UNICOS, last supported in the mid-2000s.
+ Perhaps remove them here? */
#ifndef S_ISOFD
# define S_ISOFD(p) 0
#endif
-
-/* Cray DMF (data migration facility): off line, with no data */
#ifndef S_ISOFL
# define S_ISOFL(p) 0
#endif
-/* 4.4BSD whiteout */
+/* Whiteout in 4.4 and later BSDs. This file type is observed only
+ for files opened by the superuser via fhopen. */
#ifndef S_ISWHT
# define S_ISWHT(m) 0
#endif
--
2.55.0
