hash-long-double-aux.cc (hash<long double>:: operator()(long double)): Hash both -0 and +0 to 0.

2010-02-28  Paolo Carlini  <paolo.carlini@oracle.com>

       * src/hash-long-double-aux.cc (hash<long double>::
       operator()(long double)): Hash both -0 and +0 to 0.

From-SVN: r157120

libstdc++-v3/ChangeLog

+2010-02-28  Paolo Carlini  <paolo.carlini@oracle.com>
+
+       * src/hash-long-double-aux.cc (hash<long double>::
+       operator()(long double)): Hash both -0 and +0 to 0.
+
 2010-02-25  Ed Smith-Rowland  <3dw4rd@verizon.net>
 
 	* include/bits/random.tcc (operator<<): Use max_digits10.

libstdc++-v3/src/hash-long-double-aux.cc

@@ -28,7 +28,9 @@
     size_t
     hash<long double>::operator()(long double __val) const
     {
-      size_t __result = 0;
+      // 0 and -0 both hash to zero.
+      if (__val == 0.0L)
+	return 0;
 
       int __exponent;
       __val = __builtin_frexpl(__val, &__exponent);
@@ -44,7 +46,5 @@
 
       const size_t __coeff = __SIZE_MAX__ / __LDBL_MAX_EXP__;
 
-      __result = __hibits + (size_t)__val + __coeff * __exponent;
-
-      return __result;
+      return __hibits + (size_t)__val + __coeff * __exponent;
     }