Index: libcxx/trunk/src/CMakeLists.txt
===================================================================
--- libcxx/trunk/src/CMakeLists.txt
+++ libcxx/trunk/src/CMakeLists.txt
@@ -349,7 +349,12 @@
 
   if (LIBCXX_HERMETIC_STATIC_LIBRARY)
     append_flags_if_supported(CXX_STATIC_LIBRARY_FLAGS -fvisibility=hidden)
-    append_flags_if_supported(CXX_STATIC_LIBRARY_FLAGS -fvisibility-global-new-delete-hidden)
+    # If the hermetic library doesn't define the operator new/delete functions
+    # then its code shouldn't declare them with hidden visibility.  They might
+    # actually be provided by a shared library at link time.
+    if (LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
+      append_flags_if_supported(CXX_STATIC_LIBRARY_FLAGS -fvisibility-global-new-delete-hidden)
+    endif()
     target_compile_options(cxx_static PRIVATE ${CXX_STATIC_LIBRARY_FLAGS})
     target_compile_definitions(cxx_static PRIVATE _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
   endif()
Index: llvm/trunk/utils/gn/secondary/libcxx/src/BUILD.gn
===================================================================
--- llvm/trunk/utils/gn/secondary/libcxx/src/BUILD.gn
+++ llvm/trunk/utils/gn/secondary/libcxx/src/BUILD.gn
@@ -84,6 +84,9 @@
       "_CRT_STDIO_ISO_WIDE_SPECIFIERS",
     ]
   }
+  if (!libcxx_enable_new_delete_definitions) {
+    defines += [ "_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS" ]
+  }
   if (libcxx_enable_exceptions) {
     if (current_os == "win") {
       cflags_cc += [ "/EHsc" ]
@@ -97,7 +100,7 @@
     } else {
       cflags_cc += [ "-fno-exceptions" ]
     }
-    defines += [ "-D_LIBCPP_NO_EXCEPTIONS" ]
+    defines += [ "_LIBCPP_NO_EXCEPTIONS" ]
   }
   if (!libcxx_enable_rtti) {
     if (current_os == "win") {
@@ -105,7 +108,7 @@
     } else {
       cflags_cc += [ "-fno-rtti" ]
     }
-    defines += [ "-D_LIBCPP_NO_RTTI" ]
+    defines += [ "_LIBCPP_NO_RTTI" ]
   }
 }
 
@@ -251,7 +254,9 @@
     sources = cxx_sources
     if (libcxx_hermetic_static_library) {
       cflags = [ "-fvisibility=hidden" ]
-      cflags_cc = [ "-fvisibility-global-new-delete-hidden" ]
+      if (libcxx_enable_new_delete_definitions) {
+        cflags_cc = [ "-fvisibility-global-new-delete-hidden" ]
+      }
       defines = [ "_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS" ]
     }
     deps = [