libstdc++: Make _GLIBCXX_DEBUG checks constexpr compatible

libstdc++-v3/ChangeLog:

	* include/debug/assertions.h (__glibcxx_requires_non_empty_range):
	Remove __builtin_expect.
	(__glibcxx_requires_subscript): Likewise.
	(__glibcxx_requires_nonempty): Likewise.
	* include/debug/formatter.h (__check_singular): Add C++11 constexpr
	qualification.
	* include/debug/helper_functions.h (__check_singular): Likewise. Skip
	check if constant evaluated.
	(__valid_range): Do not skip check if constant evaluated.
	* include/debug/macros.h (_GLIBCXX_DEBUG_VERIFY_COND_AT): Add
	__builtin_expect.
	(_GLIBCXX_DEBUG_VERIFY_AT_F): Use __glibcxx_assert_1.
	* testsuite/21_strings/basic_string_view/element_access/char/back_constexpr_neg.cc:
	New test.
	* testsuite/21_strings/basic_string_view/element_access/char/constexpr.cc: New test.
	* testsuite/21_strings/basic_string_view/element_access/char/constexpr_neg.cc: New test.
	* testsuite/21_strings/basic_string_view/element_access/char/front_back_constexpr.cc:
	New test.
	* testsuite/21_strings/basic_string_view/element_access/char/front_constexpr_neg.cc:
	New test.
	* testsuite/21_strings/basic_string_view/element_access/wchar_t/back_constexpr_neg.cc:
	New test.
	* testsuite/21_strings/basic_string_view/element_access/wchar_t/constexpr.cc: New test.
	* testsuite/21_strings/basic_string_view/element_access/wchar_t/constexpr_neg.cc: New test.
	* testsuite/21_strings/basic_string_view/element_access/wchar_t/front_constexpr_neg.cc:
	New test.
	* testsuite/25_algorithms/lower_bound/debug/constexpr_partitioned_neg.cc: New test.
	* testsuite/25_algorithms/lower_bound/debug/constexpr_partitioned_pred_neg.cc: New test.
	* testsuite/25_algorithms/lower_bound/debug/constexpr_valid_range_neg.cc: New test.
	* testsuite/25_algorithms/lower_bound/debug/partitioned_neg.cc: New test.
	* testsuite/25_algorithms/lower_bound/debug/partitioned_pred_neg.cc: New test.
	* testsuite/25_algorithms/upper_bound/debug/constexpr_partitioned_neg.cc: New test.
	* testsuite/25_algorithms/upper_bound/debug/constexpr_partitioned_pred_neg.cc: New test.
	* testsuite/25_algorithms/upper_bound/debug/constexpr_valid_range_neg.cc: New test.
	* testsuite/25_algorithms/upper_bound/debug/partitioned_neg.cc: New test.
	* testsuite/25_algorithms/upper_bound/debug/partitioned_pred_neg.cc: New test.

4 files changed, 26 insertions, 31 deletions

diff --git a/libstdc++-v3/include/debug/assertions.h b/libstdc++-v3/include/debug/assertions.h
index fb52e441424..16cf6bbe7ac 100644
--- a/libstdc++-v3/include/debug/assertions.h
+++ b/libstdc++-v3/include/debug/assertions.h
@@ -45,12 +45,12 @@
 
 // Verify that [_First, _Last) forms a non-empty iterator range.
 # define __glibcxx_requires_non_empty_range(_First,_Last)	\
-  __glibcxx_assert(__builtin_expect(_First != _Last, true))
+  __glibcxx_assert(_First != _Last)
 # define __glibcxx_requires_subscript(_N)	\
-  __glibcxx_assert(__builtin_expect(_N < this->size(), true))
+  __glibcxx_assert(_N < this->size())
 // Verify that the container is nonempty
 # define __glibcxx_requires_nonempty()		\
-  __glibcxx_assert(__builtin_expect(!this->empty(), true))
+  __glibcxx_assert(!this->empty())
 #endif
 
 #ifdef _GLIBCXX_DEBUG
diff --git a/libstdc++-v3/include/debug/formatter.h b/libstdc++-v3/include/debug/formatter.h
index c4283fe6047..8734ed06cb5 100644
--- a/libstdc++-v3/include/debug/formatter.h
+++ b/libstdc++-v3/include/debug/formatter.h
@@ -72,7 +72,8 @@ namespace __gnu_debug
   using std::type_info;
 
   template<typename _Iterator>
-    bool __check_singular(const _Iterator&);
+    _GLIBCXX_CONSTEXPR
+    bool __check_singular(_Iterator const&);
 
   class _Safe_sequence_base;
 
diff --git a/libstdc++-v3/include/debug/helper_functions.h b/libstdc++-v3/include/debug/helper_functions.h
index 62d5309257f..281e9c7390e 100644
--- a/libstdc++-v3/include/debug/helper_functions.h
+++ b/libstdc++-v3/include/debug/helper_functions.h
@@ -120,15 +120,29 @@ namespace __gnu_debug
   // We may have an iterator that derives from _Safe_iterator_base but isn't
   // a _Safe_iterator.
   template<typename _Iterator>
+    _GLIBCXX_CONSTEXPR
     inline bool
     __check_singular(_Iterator const& __x)
-    { return __check_singular_aux(std::__addressof(__x)); }
+    {
+      return
+#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+	__builtin_is_constant_evaluated() ? false :
+#endif
+	__check_singular_aux(std::__addressof(__x));
+    }
 
   /** Non-NULL pointers are nonsingular. */
   template<typename _Tp>
+    _GLIBCXX_CONSTEXPR
     inline bool
     __check_singular(_Tp* const& __ptr)
-    { return __ptr == 0; }
+    {
+      return
+#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+	__builtin_is_constant_evaluated() ? false :
+#endif
+	__ptr == 0;
+    }
 
   /** We say that integral types for a valid range, and defer to other
    *  routines to realize what to do with integral types instead of
@@ -225,11 +239,6 @@ namespace __gnu_debug
     __valid_range(_InputIterator __first, _InputIterator __last,
 		  typename _Distance_traits<_InputIterator>::__type& __dist)
     {
-#ifdef __cpp_lib_is_constant_evaluated
-      if (std::is_constant_evaluated())
-	// Detected by the compiler directly.
-	return true;
-#endif
       typedef typename std::__is_integer<_InputIterator>::__type _Integral;
       return __valid_range_aux(__first, __last, __dist, _Integral());
     }
@@ -253,11 +262,6 @@ namespace __gnu_debug
     inline bool
     __valid_range(_InputIterator __first, _InputIterator __last)
     {
-#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
-      if (__builtin_is_constant_evaluated())
-	// Detected by the compiler directly.
-	return true;
-#endif
       typedef typename std::__is_integer<_InputIterator>::__type _Integral;
       return __valid_range_aux(__first, __last, _Integral());
     }
diff --git a/libstdc++-v3/include/debug/macros.h b/libstdc++-v3/include/debug/macros.h
index ed606809a4d..ef4c76c747a 100644
--- a/libstdc++-v3/include/debug/macros.h
+++ b/libstdc++-v3/include/debug/macros.h
@@ -38,25 +38,15 @@
  * the user error and where the error is reported.
  *
  */
-#if 0 /* defined _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED */
-# define _GLIBCXX_DEBUG_VERIFY_COND_AT(_Cond,_ErrMsg,_File,_Line,_Func)	\
-  if (__builtin_is_constant_evaluated())				\
-    /* FIXME: Compilation error here when !_Cond. */			\
-    break;								\
-  if (! (_Cond))							\
+#define _GLIBCXX_DEBUG_VERIFY_COND_AT(_Cond,_ErrMsg,_File,_Line,_Func)	\
+  if (__builtin_expect(!bool(_Cond), false))				\
     __gnu_debug::_Error_formatter::_S_at(_File, _Line, _Func)		\
       ._ErrMsg._M_error()
-#else
-# define _GLIBCXX_DEBUG_VERIFY_COND_AT(_Cond,_ErrMsg,_File,_Line,_Func)	\
-  if (! (_Cond))							\
-    __gnu_debug::_Error_formatter::_S_at(_File, _Line, _Func)		\
-      ._ErrMsg._M_error()
-#endif
 
 #define _GLIBCXX_DEBUG_VERIFY_AT_F(_Cond,_ErrMsg,_File,_Line,_Func)	\
-  do									\
-  {									\
-    _GLIBCXX_DEBUG_VERIFY_COND_AT(_Cond,_ErrMsg,_File,_Line,_Func);	\
+  do {									\
+    __glibcxx_assert_1(_Cond)						\
+    { _GLIBCXX_DEBUG_VERIFY_COND_AT(_Cond,_ErrMsg,_File,_Line,_Func); } \
   } while (false)
 
 #define _GLIBCXX_DEBUG_VERIFY_AT(_Cond,_ErrMsg,_File,_Line)		\