diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index 72ec91949de..9314117aed8 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -487,6 +487,16 @@ namespace std
 # define _GLIBCXX_EXTERN_TEMPLATE -1
 #endif
 
+
+#if __has_builtin(__builtin_is_constant_evaluated)
+# define __glibcxx_constexpr_assert(cond) \
+  if (__builtin_is_constant_evaluated() && !bool(cond))	\
+    __builtin_unreachable() /* precondition violation detected! */
+#else
+# define __glibcxx_constexpr_assert(unevaluated)
+#endif
+
+
 // Assert.
 #if defined(_GLIBCXX_ASSERTIONS) \
   || defined(_GLIBCXX_PARALLEL) || defined(_GLIBCXX_PARALLEL_ASSERTIONS)
@@ -506,14 +516,19 @@ namespace std
 }
 #define __glibcxx_assert_impl(_Condition)			       \
   if (__builtin_expect(!bool(_Condition), false))		       \
+  {								       \
+    __glibcxx_constexpr_assert(_Condition);			       \
     std::__replacement_assert(__FILE__, __LINE__, __PRETTY_FUNCTION__, \
-			      #_Condition)
+			      #_Condition);			       \
+  }
 #endif
 
 #if defined(_GLIBCXX_ASSERTIONS)
-# define __glibcxx_assert_2(_Condition) __glibcxx_assert_impl(_Condition)
+# define __glibcxx_assert(cond) \
+  do { __glibcxx_assert_impl(cond); } while (false)
 #else
-# define __glibcxx_assert_2(_Condition)
+# define __glibcxx_assert(cond) \
+  do { __glibcxx_constexpr_assert(cond); } while (false)
 #endif
 
 // Macros for race detectors.
@@ -736,25 +751,6 @@ namespace std
 
 #undef _GLIBCXX_HAS_BUILTIN
 
-#if _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED && __cplusplus >= 201402L
-# define __glibcxx_assert_1(_Condition)		\
-    if (__builtin_is_constant_evaluated())	\
-     {						\
-       void __failed_assertion();	\
-       if (!bool(_Condition))			\
-	 __failed_assertion();	\
-     }						\
-    else
-#else
-# define __glibcxx_assert_1(_Condition)
-#endif
-
-# define __glibcxx_assert(_Condition)	  \
-  do {					  \
-    __glibcxx_assert_1(_Condition)	  \
-    { __glibcxx_assert_2(_Condition); }   \
-  } while (false)
-
 
 // PSTL configuration
 
diff --git a/libstdc++-v3/include/debug/macros.h b/libstdc++-v3/include/debug/macros.h
index 9ac52ebd09d..9e1288cf4d9 100644
--- a/libstdc++-v3/include/debug/macros.h
+++ b/libstdc++-v3/include/debug/macros.h
@@ -45,8 +45,8 @@
 
 #define _GLIBCXX_DEBUG_VERIFY_AT_F(_Cond,_ErrMsg,_File,_Line,_Func)	\
   do {									\
-    __glibcxx_assert_1(_Cond)						\
-    { _GLIBCXX_DEBUG_VERIFY_COND_AT(_Cond,_ErrMsg,_File,_Line,_Func); } \
+    __glibcxx_constexpr_assert(_Cond);					\
+    _GLIBCXX_DEBUG_VERIFY_COND_AT(_Cond,_ErrMsg,_File,_Line,_Func);	\
   } while (false)
 
 #define _GLIBCXX_DEBUG_VERIFY_AT(_Cond,_ErrMsg,_File,_Line)		\
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/back_constexpr_neg.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/back_constexpr_neg.cc
index 0f731c9a485..2da90bd954e 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/back_constexpr_neg.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/back_constexpr_neg.cc
@@ -32,4 +32,4 @@ back()
 static_assert(back() != 'a'); // { dg-error "non-constant condition" }
 
 // { dg-prune-output "in 'constexpr' expansion" }
-// { dg-prune-output "failed_assertion" }
+// { dg-prune-output "unreachable" }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/constexpr_neg.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/constexpr_neg.cc
index 5dd206f1a29..844b62277c5 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/constexpr_neg.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/constexpr_neg.cc
@@ -31,4 +31,4 @@ test()
 static_assert(test() == 0); // { dg-error "non-constant condition" }
 
 // { dg-prune-output "in 'constexpr' expansion" }
-// { dg-prune-output "failed_assertion" }
+// { dg-prune-output "unreachable" }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/front_constexpr_neg.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/front_constexpr_neg.cc
index 9c846116bb9..d6dceb61a34 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/front_constexpr_neg.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/front_constexpr_neg.cc
@@ -32,4 +32,4 @@ front()
 static_assert(front() != 'a'); // { dg-error "non-constant condition" }
 
 // { dg-prune-output "in 'constexpr' expansion" }
-// { dg-prune-output "failed_assertion" }
+// { dg-prune-output "unreachable" }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/back_constexpr_neg.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/back_constexpr_neg.cc
index 26d2d4da54b..798e1a4074d 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/back_constexpr_neg.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/back_constexpr_neg.cc
@@ -32,4 +32,4 @@ back()
 static_assert(back() != L'a'); // { dg-error "non-constant condition" }
 
 // { dg-prune-output "in 'constexpr' expansion" }
-// { dg-prune-output "failed_assertion" }
+// { dg-prune-output "unreachable" }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/constexpr_neg.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/constexpr_neg.cc
index c853dada7dc..0e22b766b3d 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/constexpr_neg.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/constexpr_neg.cc
@@ -31,4 +31,4 @@ test()
 static_assert(test() == 0); // { dg-error "non-constant condition" }
 
 // { dg-prune-output "in 'constexpr' expansion" }
-// { dg-prune-output "failed_assertion" }
+// { dg-prune-output "unreachable" }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/front_constexpr_neg.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/front_constexpr_neg.cc
index fdcabd7363d..f49774a0bdd 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/front_constexpr_neg.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/front_constexpr_neg.cc
@@ -32,4 +32,4 @@ front()
 static_assert(front() != L'a'); // { dg-error "non-constant condition" }
 
 // { dg-prune-output "in 'constexpr' expansion" }
-// { dg-prune-output "failed_assertion" }
+// { dg-prune-output "unreachable" }
diff --git a/libstdc++-v3/testsuite/23_containers/span/back_neg.cc b/libstdc++-v3/testsuite/23_containers/span/back_neg.cc
index 0289ece7a50..ce00aa8868f 100644
--- a/libstdc++-v3/testsuite/23_containers/span/back_neg.cc
+++ b/libstdc++-v3/testsuite/23_containers/span/back_neg.cc
@@ -31,5 +31,5 @@ test01(bool b)
 
 static_assert(test01(false));
 static_assert(test01(true)); // { dg-error "non-constant" }
-// { dg-error "assert" "" { target *-*-* } 0 }
+// { dg-error "unreachable" "" { target *-*-* } 0 }
 // { dg-prune-output "in 'constexpr' expansion" }
diff --git a/libstdc++-v3/testsuite/23_containers/span/front_neg.cc b/libstdc++-v3/testsuite/23_containers/span/front_neg.cc
index dfad9f8a542..a6efc7dd836 100644
--- a/libstdc++-v3/testsuite/23_containers/span/front_neg.cc
+++ b/libstdc++-v3/testsuite/23_containers/span/front_neg.cc
@@ -31,5 +31,5 @@ test01(bool b)
 
 static_assert(test01(false));
 static_assert(test01(true)); // { dg-error "non-constant" }
-// { dg-error "assert" "" { target *-*-* } 0 }
+// { dg-error "unreachable" "" { target *-*-* } 0 }
 // { dg-prune-output "in 'constexpr' expansion" }
diff --git a/libstdc++-v3/testsuite/23_containers/span/index_op_neg.cc b/libstdc++-v3/testsuite/23_containers/span/index_op_neg.cc
index 378ae05e0ea..2dce639819c 100644
--- a/libstdc++-v3/testsuite/23_containers/span/index_op_neg.cc
+++ b/libstdc++-v3/testsuite/23_containers/span/index_op_neg.cc
@@ -31,5 +31,5 @@ test01(bool b)
 
 static_assert(test01(false));
 static_assert(test01(true)); // { dg-error "non-constant" }
-// { dg-error "assert" "" { target *-*-* } 0 }
+// { dg-error "unreachable" "" { target *-*-* } 0 }
 // { dg-prune-output "in 'constexpr' expansion" }