# HG changeset patch
# User kbarrett
# Date 1420670762 18000
#      Wed Jan 07 17:46:02 2015 -0500
# Node ID bd9d999c8fb1fd866c4fa19f3d3d8eb2d6aeaac1
# Parent  e38b7790484aa7610d4483f8130d53ea8fb224b2
8067306: Improve STATIC_ASSERT
Summary: New improved implementation
Reviewed by:

diff --git a/src/share/vm/utilities/debug.hpp b/src/share/vm/utilities/debug.hpp
--- a/src/share/vm/utilities/debug.hpp
+++ b/src/share/vm/utilities/debug.hpp
@@ -225,21 +225,23 @@
 
 void warning(const char* format, ...) ATTRIBUTE_PRINTF(1, 2);
 
-#ifdef ASSERT
-// Compile-time asserts.
-template <bool> struct StaticAssert;
-template <> struct StaticAssert<true> {};
+// Compile-time asserts.  Cond must be a compile-time constant expression that
+// is convertible to bool.  STATIC_ASSERT() can be used anywhere a declaration
+// may appear.
+//
+// Implementation Note: STATIC_ASSERT_FAILURE<true> provides a value member
+// rather than type member that could be used directly in the typedef, because
+// a type member would require conditional use of "typename", depending on
+// whether Cond is dependent or not.  The use of a value member leads to the
+// use of an array type.
 
-// Only StaticAssert<true> is defined, so if cond evaluates to false we get
-// a compile time exception when trying to use StaticAssert<false>.
-#define STATIC_ASSERT(cond)                   \
-  do {                                        \
-    StaticAssert<(cond)> DUMMY_STATIC_ASSERT; \
-    (void)DUMMY_STATIC_ASSERT; /* ignore */   \
-  } while (false)
-#else
-#define STATIC_ASSERT(cond)
-#endif
+template<bool x> struct STATIC_ASSERT_FAILURE;
+template<> struct STATIC_ASSERT_FAILURE<true> { enum { value = 1 }; };
+
+#define STATIC_ASSERT(Cond) \
+  typedef char STATIC_ASSERT_FAILURE_ ## __LINE__ [ \
+    STATIC_ASSERT_FAILURE< (Cond) ? true : false >::value ] \
+  /* */
 
 // out of shared space reporting
 enum SharedSpaceType {