# lseek.m4 serial 10

dnl Copyright (C) 2007, 2009-2020 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_CANONICAL_HOST])

  AC_REQUIRE([AC_PROG_CC])

  AC_CHECK_HEADERS_ONCE([unistd.h])

  AC_CACHE_CHECK([whether lseek detects pipes], [gl_cv_func_lseek_pipe],

    [case "$host_os" in

       mingw*)

         dnl Native Windows.

         dnl The result of lseek (fd, (off_t)0, SEEK_CUR) or

         dnl SetFilePointer(handle, 0, NULL, FILE_CURRENT)

         dnl for a pipe depends on the environment: In a Cygwin 1.5

         dnl environment it succeeds (wrong); in a Cygwin 1.7 environment

         dnl it fails with a wrong errno value.

         gl_cv_func_lseek_pipe=no

         ;;

       *)

         if test $cross_compiling = no; then

           AC_LINK_IFELSE([AC_LANG_PROGRAM([[

#include <sys/types.h> /* for off_t */

#include <stdio.h> /* for SEEK_CUR */

#if HAVE_UNISTD_H

# include <unistd.h>

#else /* on Windows with MSVC */

# include <io.h>

#endif

]], [[

  /* 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 \

                 && test 1 = "`echo hi \

                   | { ./conftest$ac_exeext; echo $?; cat >/dev/null; }`"; 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(

             [AC_LANG_SOURCE([[

#if defined __BEOS__

/* 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

         ;;

     esac

    ])

  if test $gl_cv_func_lseek_pipe = no; then

    REPLACE_LSEEK=1

    AC_DEFINE([LSEEK_PIPE_BROKEN], [1],

      [Define to 1 if lseek does not detect pipes.])

  fi

  AC_REQUIRE([gl_SYS_TYPES_H])

  if test $WINDOWS_64_BIT_OFF_T = 1; then

    REPLACE_LSEEK=1

  fi

])