--- a/m4/fpending.m4
+++ b/m4/fpending.m4
@@ -14,56 +14,52 @@
 		   ac_cv_sys_pending_output_n_bytes,
       [
         fp_save_DEFS=$DEFS
-	for ac_expr in 						\
+	for ac_expr in						\
 								\
-	  '# glibc2'						\
-	  'fp->_IO_write_ptr - fp->_IO_write_base' 		\
+	    '# glibc2'						\
+	    'fp->_IO_write_ptr - fp->_IO_write_x_base'		\
 								\
-	  '# traditional Unix'					\
-	  'fp->_ptr - fp->_base' 				\
+	    '# traditional Unix'				\
+	    'fp->_ptr - fp->_base'				\
 								\
-	  '# BSD'						\
-	  'fp->_p - fp->_bf._base' 				\
+	    '# BSD'						\
+	    'fp->_p - fp->_bf._base'				\
 								\
-	  '# SCO, Unixware'					\
-	  'fp->__ptr - fp->__base' 				\
+	    '# SCO, Unixware'					\
+	    'fp->__ptr - fp->__base'				\
 								\
-	  '# old glibc?'					\
-	  'fp->__bufp - fp->__buffer' 				\
+	    '# old glibc?'					\
+	    'fp->__bufp - fp->__buffer'				\
 								\
-	  '# old glibc iostream?'				\
-	  'fp->_pptr - fp->_pbase' 				\
+	    '# old glibc iostream?'				\
+	    'fp->_pptr - fp->_pbase'				\
 								\
-	  '# VMS'						\
-	  '(*fp)->_ptr - (*fp)->_base' 				\
+	    '# VMS'						\
+	    '(*fp)->_ptr - (*fp)->_base'			\
 								\
-	  '# e.g., DGUX R4.11; the info is not available'	\
-	  1 							\
-	  ; do
-	    # Skip each embedded comment.
-	    case "$ac_expr" in '#'*) continue;; esac
-'
+	    '# e.g., DGUX R4.11; the info is not available'	\
+	    1							\
+	    ; do
+
+	  # Skip each embedded comment.
+	  case "$ac_expr" in '#'*) continue;; esac
 
-	    DEFS="$DEFS -DPENDING_OUTPUT_N_BYTES=$ac_expr"
-	    AC_TRY_COMPILE(
-	      [#include <stdio.h>
-	      ],
-	      [long unsigned int n = $ac_expr;],
-	      fp_done=yes
-            )
-	    DEFS=$fp_save_DEFS
-	    test "$fp_done" = yes && break
+	  DEFS="$DEFS -DPENDING_OUTPUT_N_BYTES=$ac_expr"
+	  AC_TRY_COMPILE(
+	    [#include <stdio.h>
+	    ],
+	    [FILE *fp = stdin; (void) ($ac_expr);],
+	    fp_done=yes
+	  )
+	  DEFS=$fp_save_DEFS
+	  test "$fp_done" = yes && break
 	done
-	AC_DEFINE_UNQUOTED(PENDING_OUTPUT_N_BYTES, $ac_expr,
-	  [the number of pending output bytes on stream `fp'])
-      ])
-  fi
 
-
-
-
-  if test $fu_cv_sys_struct_timespec = yes; then
-    AC_DEFINE_UNQUOTED(HAVE_STRUCT_TIMESPEC, 1,
-		       [Define if struct timespec is declared in <time.h>. ])
+	ac_cv_sys_pending_output_n_bytes=$ac_expr
+      ]
+    )
+    AC_DEFINE_UNQUOTED(PENDING_OUTPUT_N_BYTES,
+      $ac_cv_sys_pending_output_n_bytes,
+      [the number of pending output bytes on stream `fp'])
   fi
 ])