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-rw-r--r--m4/ungetc.m473
1 files changed, 73 insertions, 0 deletions
diff --git a/m4/ungetc.m4 b/m4/ungetc.m4
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--- /dev/null
+++ b/m4/ungetc.m4
@@ -0,0 +1,73 @@
+# ungetc.m4 serial 11
+dnl Copyright (C) 2009-2023 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 "$host_os" in
+ # Guess yes on glibc systems.
+ *-gnu* | gnu*) gl_cv_func_ungetc_works="guessing yes" ;;
+ # Guess yes on musl systems.
+ *-musl* | midipix*) gl_cv_func_ungetc_works="guessing yes" ;;
+ # Guess yes on bionic systems.
+ *-android*) gl_cv_func_ungetc_works="guessing yes" ;;
+ # Guess yes on native Windows.
+ mingw*) gl_cv_func_ungetc_works="guessing yes" ;;
+ # If we don't know, obey --enable-cross-guesses.
+ *) gl_cv_func_ungetc_works="$gl_cross_guess_normal" ;;
+ esac
+ ])
+ ])
+ gl_ftello_broken_after_ungetc=no
+ case "$gl_cv_func_ungetc_works" in
+ *yes) ;;
+ *)
+ dnl On macOS >= 10.15, where the above program fails with exit code 6,
+ dnl we fix it through an ftello override.
+ case "$host_os" in
+ darwin*) gl_ftello_broken_after_ungetc=yes ;;
+ *)
+ AC_DEFINE([FUNC_UNGETC_BROKEN], [1],
+ [Define to 1 if ungetc is broken when used on arbitrary bytes.])
+ ;;
+ esac
+ ;;
+ esac
+])