m4/fpending.m4

   1 #serial 1
   2
   3 dnl From Jim Meyering
   4 dnl Using code from emacs, based on suggestions from Paul Eggert
   5 dnl and Ulrich Drepper.
   6
   7 dnl Find out how to determine the number of pending output bytes on a stream.
   8 dnl glibc (2.1.93 and newer) and Solaris provide __fpending.  On other systems,
   9 dnl we have to grub around in the FILE struct.
  10
  11 AC_DEFUN(jm_FUNC_FPENDING,
  12 [
  13   AC_CHECK_HEADERS(stdio_ext.h)
  14   AC_REPLACE_FUNCS([__fpending])
  15   fp_headers='
  16 #     if HAVE_STDIO_EXT_H
  17 #      include <stdio_ext.h>
  18 #     endif
  19 '
  20   AC_CHECK_DECLS([__fpending], , , $fp_headers)
  21   if test $ac_cv_func___fpending = no; then
  22     AC_CACHE_CHECK(
  23               [how to determine the number of pending output bytes on a stream],
  24                    ac_cv_sys_pending_output_n_bytes,
  25       [
  26         fp_save_DEFS=$DEFS
  27         for ac_expr in                                          \
  28                                                                 \
  29             '# glibc2'                                          \
  30             'fp->_IO_write_ptr - fp->_IO_write_base'            \
  31                                                                 \
  32             '# traditional Unix'                                \
  33             'fp->_ptr - fp->_base'                              \
  34                                                                 \
  35             '# BSD'                                             \
  36             'fp->_p - fp->_bf._base'                            \
  37                                                                 \
  38             '# SCO, Unixware'                                   \
  39             'fp->__ptr - fp->__base'                            \
  40                                                                 \
  41             '# old glibc?'                                      \
  42             'fp->__bufp - fp->__buffer'                         \
  43                                                                 \
  44             '# old glibc iostream?'                             \
  45             'fp->_pptr - fp->_pbase'                            \
  46                                                                 \
  47             '# VMS'                                             \
  48             '(*fp)->_ptr - (*fp)->_base'                        \
  49                                                                 \
  50             '# e.g., DGUX R4.11; the info is not available'     \
  51             1                                                   \
  52             ; do
  53
  54           # Skip each embedded comment.
  55           case "$ac_expr" in '#'*) continue;; esac
  56
  57           DEFS="$DEFS -DPENDING_OUTPUT_N_BYTES=$ac_expr"
  58           AC_TRY_COMPILE(
  59             [#include <stdio.h>
  60             ],
  61             [FILE *fp = stdin; (void) ($ac_expr);],
  62             fp_done=yes
  63           )
  64           DEFS=$fp_save_DEFS
  65           test "$fp_done" = yes && break
  66         done
  67
  68         ac_cv_sys_pending_output_n_bytes=$ac_expr
  69       ]
  70     )
  71     AC_DEFINE_UNQUOTED(PENDING_OUTPUT_N_BYTES,
  72       $ac_cv_sys_pending_output_n_bytes,
  73       [the number of pending output bytes on stream `fp'])
  74   fi
  75 ])