Use fstatfs to determine whether a file is a procfs file.

ch.c

@@ -26,6 +26,10 @@ extern dev_t curr_dev;
 extern ino_t curr_ino;
 #endif
 
+#if HAVE_STATFS
+#include <sys/statfs.h>
+#endif
+
 typedef POSITION BLOCKNUM;
 
 public int ignore_eoi;
@@ -684,6 +688,30 @@ ch_setbufspace(bufspace)
  }
 }
 
+/*
+ */
+ static int
+trust_size(file, fsize)
+ int file;
+ POSITION fsize;
+{
+ if (fsize != 0)
+ {
+ /* Nontrustable files always say their size is 0, so this isn't one. */
+ return 1;
+ }
+#if HAVE_STATFS
+ /* Cannot trust procfs files. */
+ struct statfs st;
+ if (fstatfs(file, &st) == 0)
+ return (st.f_type != PROC_SUPER_MAGIC);
+#else
+ (void) file;
+#endif
+ /* If we can't tell the file type, be safe and say it's not trustable. */
+ return 0;
+}
+
 /*
  * Flush (discard) any saved file state, including buffer contents.
  */
@@ -732,7 +760,7 @@ ch_flush(VOID_PARAM)
  * data. They are sometimes, but not always, seekable.
  * Force them to be non-seekable here.
  */
- if (ch_fsize == 0)
+ if (!trust_size(ch_file, ch_fsize))
  {
  ch_fsize = NULL_POSITION;
  ch_flags &= ~CH_CANSEEK;

configure.ac

@@ -217,6 +217,8 @@ AH_TEMPLATE([HAVE_CONST],
  [Define HAVE_CONST if your compiler supports the "const" modifier.])
 AH_TEMPLATE([HAVE_STAT_INO],
  [Define HAVE_STAT_INO if your struct stat has st_ino and st_dev.])
+AH_TEMPLATE([HAVE_STATFS],
+ [Define HAVE_STATFS if have have fstatfs with f_type.])
 AH_TEMPLATE([HAVE_TIME_T],
  [Define HAVE_TIME_T if your system supports the "time_t" type.])
 AH_TEMPLATE([HAVE_STRERROR],
@@ -266,6 +268,10 @@ AC_TRY_COMPILE([#include <sys/types.h>
 #include <sys/stat.h>],
  [struct stat s; dev_t dev = s.st_dev; ino_t ino = s.st_ino;],
  [AC_MSG_RESULT(yes); AC_DEFINE(HAVE_STAT_INO)], [AC_MSG_RESULT(no)])
+AC_MSG_CHECKING(for statfs)
+AC_TRY_COMPILE([#include <sys/statfs.h>],
+ [struct statfs s; s.f_type = PROC_SUPER_MAGIC; (void) fstatfs(0,&s); ],
+ [AC_MSG_RESULT(yes); AC_DEFINE(HAVE_STATFS)], [AC_MSG_RESULT(no)])
 
 # Checks for ANSI function prototypes.
 AC_MSG_CHECKING(for ANSI function prototypes)