Re: Fix operator precedence in _ShiftMin1.

[Ed Smith-Rowland <3dw4rd at verizon dot net>]

Smith-Rowland, Edward M wrote:
> All,
>
> The following fixes a bonehead mistake in operator precedence in
> the _ShiftMin1 tool used by mersenne_twister_engine and others.
>
> I think this might be obvious and may be the source of other mistakes.
>
> I am bootstrapping and regtesting now but this might be obvious.
>
> Ed
>
>   
All,

There was one mistake left:
Change this:
         __gnu_cxx::__numeric_traits<_UIntType>::max;
to this:
         __gnu_cxx::__numeric_traits<_UIntType>::__max;

Add two underscores to max.

Here is the new patchlet.

This doesn't really have much to do with 39629.  Sorry for the noise.

Ed

Index: include/bits/random.h
===================================================================
--- include/bits/random.h	(revision 145501)
+++ include/bits/random.h	(working copy)
@@ -75,17 +75,18 @@
 
     // XXX need constexpr
     template<typename _UIntType, size_t __w,
-	     bool = __w <static_cast<size_t>
-			 (std::numeric_limits<_UIntType>::digits)>
+	     bool = __w < static_cast<size_t>
+			  (std::numeric_limits<_UIntType>::digits)>
       struct _ShiftMin1
-      { 
+      {
 	static const _UIntType __value =
 	  __gnu_cxx::__numeric_traits<_UIntType>::__max;
       };
 
     template<typename _UIntType, size_t __w>
       struct _ShiftMin1<_UIntType, __w, true>
-      { static const _UIntType __value = _UIntType(1) << __w - _UIntType(1); };
+      { static const _UIntType __value
+                               = (_UIntType(1) << __w) - _UIntType(1); };
 
     template<typename _Tp, _Tp __a, _Tp __c, _Tp __m, bool>
       struct _Mod;
@@ -389,7 +390,7 @@
     {
       __glibcxx_class_requires(_UIntType, _UnsignedIntegerConcept)
 
-      static_assert(__m >= 1U, 
+      static_assert(__m >= 1U,
 		    "mersenne_twister_engine template arguments out of bounds");
       static_assert(__n >= __m,
 		    "mersenne_twister_engine template arguments out of bounds");
@@ -403,18 +404,15 @@
 		    "mersenne_twister_engine template arguments out of bounds");
       static_assert(__w >= __l,
 		    "mersenne_twister_engine template arguments out of bounds");
-      static_assert(__w <= static_cast<size_t>(numeric_limits<_UIntType>::digits), 
+      static_assert(__w
+                    <= static_cast<size_t>(numeric_limits<_UIntType>::digits),
 		    "mersenne_twister_engine template arguments out of bounds");
-
-#if 0
-      // XXX
       static_assert(__a <= __detail::_ShiftMin1<_UIntType, __w>::__value,
 		    "mersenne_twister_engine template arguments out of bounds");
       static_assert(__b <= __detail::_ShiftMin1<_UIntType, __w>::__value,
 		    "mersenne_twister_engine template arguments out of bounds");
       static_assert(__c <= __detail::_ShiftMin1<_UIntType, __w>::__value,
 		    "mersenne_twister_engine template arguments out of bounds");
-#endif
 
     public:
       /** The type of the generated random value. */
Index: testsuite/26_numerics/random/mersenne_twister_engine/cons/default.cc
===================================================================
--- testsuite/26_numerics/random/mersenne_twister_engine/cons/default.cc	(revision 145501)
+++ testsuite/26_numerics/random/mersenne_twister_engine/cons/default.cc	(working copy)
@@ -40,7 +40,7 @@
     0xefc60000ul, 18, 1812433253ul> x;
 
   VERIFY( x.min() == 0 );
-  // XXX  VERIFY( x.max() == 4294967295ul);
+  VERIFY( x.max() == 4294967295ul);
   VERIFY( x() == 3499211612ul );
 }