base64: fix off-by-one buffer size bug

[gnulib.git] / m4 / fflush.m4

diff --git a/m4/fflush.m4 b/m4/fflush.m4
old mode 100755 (executable)
new mode 100644 (file)
index f796a55..a91ee0b
--- a/m4/fflush.m4
+++ b/m4/fflush.m4
@@ -1,6 +1,6 @@
-# fflush.m4 serial 4
+# fflush.m4 serial 12
 
-# Copyright (C) 2007 Free Software Foundation, Inc.
+# Copyright (C) 2007-2011 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.
@@ -12,6 +12,18 @@ dnl unread input on seekable streams, rather than C99 undefined semantics.
 
 AC_DEFUN([gl_FUNC_FFLUSH],
 [
+  AC_REQUIRE([gl_STDIO_H_DEFAULTS])
+  gl_FUNC_FFLUSH_STDIN
+  if test $gl_cv_func_fflush_stdin = no; then
+    REPLACE_FFLUSH=1
+  fi
+])
+
+dnl Determine whether fflush works on input streams.
+dnl Sets gl_cv_func_fflush_stdin.
+
+AC_DEFUN([gl_FUNC_FFLUSH_STDIN],
+[
   AC_CACHE_CHECK([whether fflush works on input streams],
     [gl_cv_func_fflush_stdin],
     [echo hello world > conftest.txt
@@ -20,33 +32,50 @@ AC_DEFUN([gl_FUNC_FFLUSH],
 #include <stdio.h>
 #include <unistd.h>
        ]], [[FILE *f = fopen ("conftest.txt", "r");
-        char buffer[10];
-        int fd = fileno (f);
-        if (!f || 0 > fd || 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.  */
-        if (fflush (f) != 0 || fseek (f, 0, SEEK_CUR) != 0)
-          return 4;
-        return !(lseek (fd, 0, SEEK_CUR) == 5);
+         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.  This is wrong for
-      dnl at least glibc and cygwin; but lib/fflush.c takes this into account.
+     [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],
+# Prerequisites of lib/fflush.c.
+AC_DEFUN([gl_PREREQ_FFLUSH],
 [
-  AC_LIBOBJ([fflush])
-  AC_LIBOBJ([fseeko])
-  AC_REQUIRE([gl_STDIO_H_DEFAULTS])
-  REPLACE_FFLUSH=1
-  REPLACE_FSEEKO=1
+  AC_REQUIRE([AC_C_INLINE])
+  :
 ])