m4/fpending.m4

   1 # serial 21
   2
   3 # Copyright (C) 2000-2001, 2004-2014 Free Software Foundation, Inc.
   4 # This file is free software; the Free Software Foundation
   5 # gives unlimited permission to copy and/or distribute it,
   6 # with or without modifications, as long as this notice is preserved.
   7
   8 dnl From Jim Meyering
   9 dnl Using code from emacs, based on suggestions from Paul Eggert
  10 dnl and Ulrich Drepper.
  11
  12 dnl Find out how to determine the number of pending output bytes on a stream.
  13 dnl glibc (2.1.93 and newer) and Solaris provide __fpending.  On other systems,
  14 dnl we have to grub around in the FILE struct.
  15
  16 AC_DEFUN([gl_FUNC_FPENDING],
  17 [
  18   AC_CHECK_HEADERS_ONCE([stdio_ext.h])
  19   fp_headers='
  20     #include <stdio.h>
  21     #if HAVE_STDIO_EXT_H
  22     # include <stdio_ext.h>
  23     #endif
  24   '
  25   AC_CACHE_CHECK([for __fpending], [gl_cv_func___fpending],
  26     [
  27       AC_LINK_IFELSE(
  28         [AC_LANG_PROGRAM([$fp_headers],
  29            [[return ! __fpending (stdin);]])],
  30         [gl_cv_func___fpending=yes],
  31         [gl_cv_func___fpending=no])
  32     ])
  33   if test $gl_cv_func___fpending = yes; then
  34     AC_CHECK_DECLS([__fpending], [], [], [$fp_headers])
  35   fi
  36 ])
  37
  38 AC_DEFUN([gl_PREREQ_FPENDING],
  39 [
  40   AC_CACHE_CHECK(
  41               [how to determine the number of pending output bytes on a stream],
  42                  ac_cv_sys_pending_output_n_bytes,
  43     [
  44       for ac_expr in                                                    \
  45                                                                         \
  46           '# glibc2'                                                    \
  47           'fp->_IO_write_ptr - fp->_IO_write_base'                      \
  48                                                                         \
  49           '# traditional Unix'                                          \
  50           'fp->_ptr - fp->_base'                                        \
  51                                                                         \
  52           '# BSD'                                                       \
  53           'fp->_p - fp->_bf._base'                                      \
  54                                                                         \
  55           '# SCO, Unixware'                                             \
  56           '(fp->__ptr ? fp->__ptr - fp->__base : 0)'                    \
  57                                                                         \
  58           '# QNX'                                                       \
  59           '(fp->_Mode & 0x2000 /*_MWRITE*/ ? fp->_Next - fp->_Buf : 0)' \
  60                                                                         \
  61           '# old glibc?'                                                \
  62           'fp->__bufp - fp->__buffer'                                   \
  63                                                                         \
  64           '# old glibc iostream?'                                       \
  65           'fp->_pptr - fp->_pbase'                                      \
  66                                                                         \
  67           '# emx+gcc'                                                   \
  68           'fp->_ptr - fp->_buffer'                                      \
  69                                                                         \
  70           '# Minix'                                                     \
  71           'fp->_ptr - fp->_buf'                                         \
  72                                                                         \
  73           '# Plan9'                                                     \
  74           'fp->wp - fp->buf'                                            \
  75                                                                         \
  76           '# VMS'                                                       \
  77           '(*fp)->_ptr - (*fp)->_base'                                  \
  78                                                                         \
  79           '# e.g., DGUX R4.11; the info is not available'               \
  80           1                                                             \
  81           ; do
  82
  83         # Skip each embedded comment.
  84         case "$ac_expr" in '#'*) continue;; esac
  85
  86         AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stdio.h>]],
  87           [[FILE *fp = stdin; (void) ($ac_expr);]])],
  88           [fp_done=yes]
  89         )
  90         test "$fp_done" = yes && break
  91       done
  92
  93       ac_cv_sys_pending_output_n_bytes=$ac_expr
  94     ]
  95   )
  96   AC_DEFINE_UNQUOTED([PENDING_OUTPUT_N_BYTES],
  97     $ac_cv_sys_pending_output_n_bytes,
  98     [the number of pending output bytes on stream 'fp'])
  99 ])