# ungetc.m4 serial 8

dnl Copyright (C) 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_ONCE([gl_FUNC_UNGETC_WORKS],

[

  AC_REQUIRE([AC_PROG_CC])

  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles

  AC_CACHE_CHECK([whether ungetc works on arbitrary bytes],

    [gl_cv_func_ungetc_works],

    [AC_RUN_IFELSE([AC_LANG_PROGRAM([[

#include <stdio.h>

      ]], [FILE *f;

           if (!(f = fopen ("conftest.tmp", "w+")))

             return 1;

           if (fputs ("abc", f) < 0)

             { fclose (f); return 2; }

           rewind (f);

           if (fgetc (f) != 'a')

             { fclose (f); return 3; }

           if (fgetc (f) != 'b')

             { fclose (f); return 4; }

           if (ungetc ('d', f) != 'd')

             { fclose (f); return 5; }

           if (ftell (f) != 1)

             { fclose (f); return 6; }

           if (fgetc (f) != 'd')

             { fclose (f); return 7; }

           if (ftell (f) != 2)

             { fclose (f); return 8; }

           if (fseek (f, 0, SEEK_CUR) != 0)

             { fclose (f); return 9; }

           if (ftell (f) != 2)

             { fclose (f); return 10; }

           if (fgetc (f) != 'c')

             { fclose (f); return 11; }

           fclose (f);

           remove ("conftest.tmp");])],

        [gl_cv_func_ungetc_works=yes], [gl_cv_func_ungetc_works=no],

        [case "$host_os" in

                          # Guess yes on glibc systems.

           *-gnu* | gnu*) gl_cv_func_ungetc_works="guessing yes" ;;

                          # Guess yes on musl systems.

           *-musl*)       gl_cv_func_ungetc_works="guessing yes" ;;

                          # Guess yes on bionic systems.

           *-android*)    gl_cv_func_ungetc_works="guessing yes" ;;

                          # Guess yes on native Windows.

           mingw*)        gl_cv_func_ungetc_works="guessing yes" ;;

                          # If we don't know, obey --enable-cross-guesses.

           *)             gl_cv_func_ungetc_works="$gl_cross_guess_normal" ;;

         esac

        ])

    ])

  case "$gl_cv_func_ungetc_works" in

    *yes) ;;

    *)

      AC_DEFINE([FUNC_UNGETC_BROKEN], [1],

        [Define to 1 if ungetc is broken when used on arbitrary bytes.])

      ;;

  esac

])