diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -162,11 +162,6 @@
 // reduces the number of weak definitions generated in programs that use
 // iostreams by providing a single strong definition in the shared library.
 #    define _LIBCPP_ABI_ENABLE_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1
-
-// Define a key function for `bad_function_call` in the library, to centralize
-// its vtable and typeinfo to libc++ rather than having all other libraries
-// using that class define their own copies.
-#    define _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
 #  endif
 
 #  define _LIBCPP_TOSTRING2(x) #x
diff --git a/libcxx/include/__functional/function.h b/libcxx/include/__functional/function.h
--- a/libcxx/include/__functional/function.h
+++ b/libcxx/include/__functional/function.h
@@ -50,14 +50,7 @@
     : public exception
 {
 public:
-// Note that when a key function is not used, every translation unit that uses
-// bad_function_call will end up containing a weak definition of the vtable and
-// typeinfo.
-#ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
-    ~bad_function_call() _NOEXCEPT override;
-#else
-    ~bad_function_call() _NOEXCEPT override {}
-#endif
+    ~bad_function_call() _NOEXCEPT override = default;
 
 #ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_GOOD_WHAT_MESSAGE
     const char* what() const _NOEXCEPT override;
diff --git a/libcxx/src/functional.cpp b/libcxx/src/functional.cpp
--- a/libcxx/src/functional.cpp
+++ b/libcxx/src/functional.cpp
@@ -10,12 +10,6 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
-bad_function_call::~bad_function_call() noexcept
-{
-}
-#endif
-
 #ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_GOOD_WHAT_MESSAGE
 const char*
 bad_function_call::what() const noexcept