# ftello.m4 serial 13

dnl Copyright (C) 2007-2020 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_FTELLO],

[

  AC_REQUIRE([gl_STDIO_H_DEFAULTS])

  AC_REQUIRE([AC_PROG_CC])

  AC_REQUIRE([gl_STDIN_LARGE_OFFSET])

  AC_REQUIRE([gl_SYS_TYPES_H])

  dnl Persuade glibc <stdio.h> to declare ftello().

  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])

  AC_CHECK_DECLS_ONCE([ftello])

  if test $ac_cv_have_decl_ftello = no; then

    HAVE_DECL_FTELLO=0

  fi

  AC_CACHE_CHECK([for ftello], [gl_cv_func_ftello],

    [

      AC_LINK_IFELSE(

        [AC_LANG_PROGRAM(

           [[#include <stdio.h>]],

           [[ftello (stdin);]])],

        [gl_cv_func_ftello=yes],

        [gl_cv_func_ftello=no])

    ])

  if test $gl_cv_func_ftello = no; then

    HAVE_FTELLO=0

  else

    if test $WINDOWS_64_BIT_OFF_T = 1; then

      REPLACE_FTELLO=1

    fi

    if test $gl_cv_var_stdin_large_offset = no; then

      REPLACE_FTELLO=1

    fi

    if test $REPLACE_FTELLO = 0; then

      dnl Detect bug on Solaris.

      dnl ftell and ftello produce incorrect results after putc that followed a

      dnl getc call that reached EOF on Solaris. This is because the _IOREAD

      dnl flag does not get cleared in this case, even though _IOWRT gets set,

      dnl and ftell and ftello look whether the _IOREAD flag is set.

      AC_REQUIRE([AC_CANONICAL_HOST])

      AC_CACHE_CHECK([whether ftello works],

        [gl_cv_func_ftello_works],

        [

          dnl Initial guess, used when cross-compiling or when /dev/tty cannot

          dnl be opened.

changequote(,)dnl

          case "$host_os" in

                      # Guess no on Solaris.

            solaris*) gl_cv_func_ftello_works="guessing no" ;;

                      # Guess yes on native Windows.

            mingw*)   gl_cv_func_ftello_works="guessing yes" ;;

                      # Guess yes otherwise.

            *)        gl_cv_func_ftello_works="guessing yes" ;;

          esac

changequote([,])dnl

          AC_RUN_IFELSE(

            [AC_LANG_SOURCE([[

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#define TESTFILE "conftest.tmp"

int

main (void)

{

  FILE *fp;

  /* Create a file with some contents.  */

  fp = fopen (TESTFILE, "w");

  if (fp == NULL)

    return 70;

  if (fwrite ("foogarsh", 1, 8, fp) < 8)

    { fclose (fp); return 71; }

  if (fclose (fp))

    return 72;

  /* The file's contents is now "foogarsh".  */

  /* Try writing after reading to EOF.  */

  fp = fopen (TESTFILE, "r+");

  if (fp == NULL)

    return 73;

  if (fseek (fp, -1, SEEK_END))

    { fclose (fp); return 74; }

  if (!(getc (fp) == 'h'))

    { fclose (fp); return 1; }

  if (!(getc (fp) == EOF))

    { fclose (fp); return 2; }

  if (!(ftell (fp) == 8))

    { fclose (fp); return 3; }

  if (!(ftell (fp) == 8))

    { fclose (fp); return 4; }

  if (!(putc ('!', fp) == '!'))

    { fclose (fp); return 5; }

  if (!(ftell (fp) == 9))

    { fclose (fp); return 6; }

  if (!(fclose (fp) == 0))

    return 7;

  fp = fopen (TESTFILE, "r");

  if (fp == NULL)

    return 75;

  {

    char buf[10];

    if (!(fread (buf, 1, 10, fp) == 9))

      { fclose (fp); return 10; }

    if (!(memcmp (buf, "foogarsh!", 9) == 0))

      { fclose (fp); return 11; }

  }

  if (!(fclose (fp) == 0))

    return 12;

  /* The file's contents is now "foogarsh!".  */

  return 0;

}]])],

            [gl_cv_func_ftello_works=yes],

            [gl_cv_func_ftello_works=no], [:])

        ])

      case "$gl_cv_func_ftello_works" in

        *yes) ;;

        *)

          REPLACE_FTELLO=1

          AC_DEFINE([FTELLO_BROKEN_AFTER_SWITCHING_FROM_READ_TO_WRITE], [1],

            [Define to 1 if the system's ftello function has the Solaris bug.])

          ;;

      esac

    fi

  fi

])

# Prerequisites of lib/ftello.c.

AC_DEFUN([gl_PREREQ_FTELLO],

[

  dnl Native Windows has the function _ftelli64. mingw hides it, but mingw64

  dnl makes it usable again.

  AC_CHECK_FUNCS([_ftelli64])

])