--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2006-11-07  Paul Eggert  <eggert@cs.ucla.edu>
 
+	* m4/longlong.m4 (AC_TYPE_LONG_LONG_INT): Detect bug in
+	Tandem NonStop Kernel (OSS) cc -O circa 2004, reported by
+	Matthew Woehlke.
+
 	* lib/xalloc.h (XMALLOC, XNMALLOC, XZALLOC, XCALLOC): Move
 	definitions up, to avoid colliding with change below.
 	(static_inline) [HAVE_INLINE]: New macro.

--- a/m4/longlong.m4
+++ b/m4/longlong.m4
@@ -1,4 +1,4 @@
-# longlong.m4 serial 8
+# longlong.m4 serial 9
 dnl Copyright (C) 1999-2006 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -11,7 +11,7 @@
 # assume 2.61 everywhere.
 
 # Note: If the type 'long long int' exists but is only 32 bits large
-# (as on some very old compilers), AC_TYPE_LONG_LONG_INT will not be
+# (as on some very old compilers), HAVE_LONG_LONG_INT will not be
 # defined. In this case you can treat 'long long int' like 'long int'.
 
 AC_DEFUN([AC_TYPE_LONG_LONG_INT],
@@ -28,9 +28,33 @@
 	  [[long long int llmax = 9223372036854775807ll;
 	    return ((ll << 63) | (ll >> 63) | (ll < i) | (ll > i)
 		    | (llmax / ll) | (llmax % ll));]])],
-       [ac_cv_type_long_long_int=yes],
+       [dnl This catches a bug in Tandem NonStop Kernel (OSS) cc -O circa 2004.
+	dnl If cross compiling, assume the bug isn't important, since
+	dnl nobody cross compiles for this platform as far as we know.
+        AC_RUN_IFELSE(
+	  [AC_LANG_PROGRAM(
+	     [[@%:@include <limits.h>
+	       @%:@ifndef LLONG_MAX
+	       @%:@ define HALF \
+			(1LL << (sizeof (long long int) * CHAR_BIT - 2))
+	       @%:@ define LLONG_MAX (HALF - 1 + HALF)
+	       @%:@endif]],
+	     [[long long int n = 1;
+	       int i;
+	       for (i = 0; ; i++)
+		 {
+		   long long int m = n << i;
+		   if (m >> i != n)
+		     return 1;
+		   if (LLONG_MAX / 2 < m)
+		     break;
+		 }
+	       return 0;]])],
+	  [ac_cv_type_long_long_int=yes],
+	  [ac_cv_type_long_long_int=no],
+	  [ac_cv_type_long_long_int=cross-compiling])],
        [ac_cv_type_long_long_int=no])])
-  if test $ac_cv_type_long_long_int = yes; then
+  if test $ac_cv_type_long_long_int != no; then
     AC_DEFINE([HAVE_LONG_LONG_INT], 1,
       [Define to 1 if the system has the type `long long int'.])
   fi