Imported Upstream version 1.3.14

[debian/gzip] / m4 / fflush.m4

diff --git a/m4/fflush.m4 b/m4/fflush.m4
new file mode 100644 (file)
index 0000000..da30e1f
--- /dev/null
+++ b/m4/fflush.m4
@@ -0,0 +1,82 @@
+# fflush.m4 serial 7
+
+# Copyright (C) 2007-2009 Free Software Foundation, Inc.
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+dnl From Eric Blake
+
+dnl Find out how to obey POSIX semantics of fflush(stdin) discarding
+dnl unread input on seekable streams, rather than C99 undefined semantics.
+
+AC_DEFUN([gl_FUNC_FFLUSH],
+[
+  AC_CACHE_CHECK([whether fflush works on input streams],
+    [gl_cv_func_fflush_stdin],
+    [echo hello world > conftest.txt
+     AC_RUN_IFELSE([AC_LANG_PROGRAM(
+       [[
+#include <stdio.h>
+#include <unistd.h>
+       ]], [[FILE *f = fopen ("conftest.txt", "r");
+        char buffer[10];
+        int fd;
+        int c;
+        if (f == NULL)
+          return 1;
+        fd = fileno (f);
+        if (fd < 0 || fread (buffer, 1, 5, f) != 5)
+          return 2;
+        /* For deterministic results, ensure f read a bigger buffer.  */
+        if (lseek (fd, 0, SEEK_CUR) == 5)
+          return 3;
+        /* POSIX requires fflush-fseek to set file offset of fd.  This fails
+           on BSD systems and on mingw.  */
+        if (fflush (f) != 0 || fseek (f, 0, SEEK_CUR) != 0)
+          return 4;
+        if (lseek (fd, 0, SEEK_CUR) != 5)
+          return 5;
+        /* Verify behaviour of fflush after ungetc. See
+           <http://www.opengroup.org/austin/aardvark/latest/xshbug3.txt>  */
+        /* Verify behaviour of fflush after a backup ungetc.  This fails on
+           mingw.  */
+        c = fgetc (f);
+        ungetc (c, f);
+        fflush (f);
+        if (fgetc (f) != c)
+          return 6;
+        /* Verify behaviour of fflush after a non-backup ungetc.  This fails
+           on glibc 2.8 and on BSD systems.  */
+        c = fgetc (f);
+        ungetc ('@', f);
+        fflush (f);
+        if (fgetc (f) != c)
+          return 7;
+        return 0;
+       ]])], [gl_cv_func_fflush_stdin=yes], [gl_cv_func_fflush_stdin=no],
+     [dnl Pessimistically assume fflush is broken.
+      gl_cv_func_fflush_stdin=no])
+     rm conftest.txt
+    ])
+  if test $gl_cv_func_fflush_stdin = no; then
+    gl_REPLACE_FFLUSH
+  fi
+])
+
+AC_DEFUN([gl_REPLACE_FFLUSH],
+[
+  AC_LIBOBJ([fflush])
+  AC_LIBOBJ([fseeko])
+  AC_REQUIRE([gl_STDIO_H_DEFAULTS])
+  REPLACE_FFLUSH=1
+  REPLACE_FSEEKO=1
+  gl_PREREQ_FFLUSH
+])
+
+# Prerequisites of lib/fflush.c.
+AC_DEFUN([gl_PREREQ_FFLUSH],
+[
+  AC_REQUIRE([AC_C_INLINE])
+  :
+])