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-rw-r--r--gl/m4/ungetc.m473
1 files changed, 73 insertions, 0 deletions
diff --git a/gl/m4/ungetc.m4 b/gl/m4/ungetc.m4
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1# ungetc.m4 serial 10
2dnl Copyright (C) 2009-2023 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7AC_DEFUN_ONCE([gl_FUNC_UNGETC_WORKS],
8[
9 AC_REQUIRE([AC_PROG_CC])
10 AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
11
12 AC_CACHE_CHECK([whether ungetc works on arbitrary bytes],
13 [gl_cv_func_ungetc_works],
14 [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
15#include <stdio.h>
16 ]], [[FILE *f;
17 if (!(f = fopen ("conftest.tmp", "w+")))
18 return 1;
19 if (fputs ("abc", f) < 0)
20 { fclose (f); return 2; }
21 rewind (f);
22 if (fgetc (f) != 'a')
23 { fclose (f); return 3; }
24 if (fgetc (f) != 'b')
25 { fclose (f); return 4; }
26 if (ungetc ('d', f) != 'd')
27 { fclose (f); return 5; }
28 if (ftell (f) != 1)
29 { fclose (f); return 6; }
30 if (fgetc (f) != 'd')
31 { fclose (f); return 7; }
32 if (ftell (f) != 2)
33 { fclose (f); return 8; }
34 if (fseek (f, 0, SEEK_CUR) != 0)
35 { fclose (f); return 9; }
36 if (ftell (f) != 2)
37 { fclose (f); return 10; }
38 if (fgetc (f) != 'c')
39 { fclose (f); return 11; }
40 fclose (f);
41 remove ("conftest.tmp");
42 ]])],
43 [gl_cv_func_ungetc_works=yes], [gl_cv_func_ungetc_works=no],
44 [case "$host_os" in
45 # Guess yes on glibc systems.
46 *-gnu* | gnu*) gl_cv_func_ungetc_works="guessing yes" ;;
47 # Guess yes on musl systems.
48 *-musl*) gl_cv_func_ungetc_works="guessing yes" ;;
49 # Guess yes on bionic systems.
50 *-android*) gl_cv_func_ungetc_works="guessing yes" ;;
51 # Guess yes on native Windows.
52 mingw*) gl_cv_func_ungetc_works="guessing yes" ;;
53 # If we don't know, obey --enable-cross-guesses.
54 *) gl_cv_func_ungetc_works="$gl_cross_guess_normal" ;;
55 esac
56 ])
57 ])
58 gl_ftello_broken_after_ungetc=no
59 case "$gl_cv_func_ungetc_works" in
60 *yes) ;;
61 *)
62 dnl On macOS >= 10.15, where the above program fails with exit code 6,
63 dnl we fix it through an ftello override.
64 case "$host_os" in
65 darwin*) gl_ftello_broken_after_ungetc=yes ;;
66 *)
67 AC_DEFINE([FUNC_UNGETC_BROKEN], [1],
68 [Define to 1 if ungetc is broken when used on arbitrary bytes.])
69 ;;
70 esac
71 ;;
72 esac
73])