lseek.m4

gnu tar 源码包。 tar 软件是 Unix 系统下的一个打包软件

# lseek.m4 serial 4
dnl Copyright (C) 2007 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

AC_DEFUN([gl_FUNC_LSEEK],
[
  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
  AC_REQUIRE([AC_PROG_CC])
  AC_CACHE_CHECK([whether lseek detects pipes], [gl_cv_func_lseek_pipe],
    [if test $cross_compiling = no; then
       AC_LINK_IFELSE([
#include <sys/types.h> /* for off_t */
#include <stdio.h> /* for SEEK_CUR */
#include <unistd.h>
int main ()
{
  /* Exit with success only if stdin is seekable.  */
  return lseek (0, (off_t)0, SEEK_CUR) < 0;
}],
	 [if test -s conftest$ac_exeext \
	     && ./conftest$ac_exeext < conftest.$ac_ext \
	     && { echo hi | ./conftest$ac_exeext; test $? = 1; }; then
	    gl_cv_func_lseek_pipe=yes
	  else
	    gl_cv_func_lseek_pipe=no
	  fi],
	 [gl_cv_func_lseek_pipe=no])
     else
       AC_COMPILE_IFELSE([
#if ((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__) || defined __BEOS__
/* mingw and BeOS mistakenly return 0 when trying to seek on pipes.  */
  Choke me.
#endif],
	 [gl_cv_func_lseek_pipe=yes], [gl_cv_func_lseek_pipe=no])
     fi])
  if test $gl_cv_func_lseek_pipe = no; then
    gl_REPLACE_LSEEK
  fi
])

AC_DEFUN([gl_REPLACE_LSEEK],
[
  AC_LIBOBJ([lseek])
  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
  REPLACE_LSEEK=1
  AC_DEFINE([LSEEK_PIPE_BROKEN], [1],
	    [Define to 1 if lseek does not detect pipes.])
])