#serial 1

dnl From Jim Meyering
dnl Using code from emacs, based on suggestions from Paul Eggert
dnl and Ulrich Drepper.

AC_DEFUN(jm_FUNC_FPENDING,
[
  AC_CHECK_HEADERS(stdio_ext.h)
  AC_REPLACE_FUNCS([__fpending])
  if test $ac_cv_func___fpending = no; then
    AC_CACHE_CHECK(
	      [how to determine the number of pending output bytes on a stream],
		   ac_cv_sys_pending_output_n_bytes,
      [
        fp_save_DEFS=$DEFS
	for ac_expr in						\
								\
	    '# glibc2'						\
	    'fp->_IO_write_ptr - fp->_IO_write_x_base'		\
								\
	    '# traditional Unix'				\
	    'fp->_ptr - fp->_base'				\
								\
	    '# BSD'						\
	    'fp->_p - fp->_bf._base'				\
								\
	    '# SCO, Unixware'					\
	    'fp->__ptr - fp->__base'				\
								\
	    '# old glibc?'					\
	    'fp->__bufp - fp->__buffer'				\
								\
	    '# old glibc iostream?'				\
	    'fp->_pptr - fp->_pbase'				\
								\
	    '# 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

	  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_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
])