3 files changed, 17 insertions, 5 deletions
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 2c0fc4e7e3d..2347cfebf0b 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4784,6 +4784,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       CmdArgs.push_back("-fforce-enable-int128");
   }
 
+  if (Args.hasFlag(options::OPT_fcomplete_member_pointers,
+                   options::OPT_fno_complete_member_pointers, false))
+    CmdArgs.push_back("-fcomplete-member-pointers");
+
   // Finally add the compile command to the compilation.
   if (Args.hasArg(options::OPT__SLASH_fallback) &&
       Output.getType() == types::TY_Object &&
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 75d6a26cdb7..594164332ec 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -2754,6 +2754,8 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
           << A->getAsString(Args) << A->getValue();
     }
   }
+
+  Opts.CompleteMemberPointers = Args.hasArg(OPT_fcomplete_member_pointers);
 }
 
 static bool isStrictlyPreprocessorAction(frontend::ActionKind Action) {
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 7e8f9b19e3d..b5a90af39ba 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -7585,11 +7585,17 @@ bool Sema::RequireCompleteTypeImpl(SourceLocation Loc, QualType T,
   //  assert(!T->isDependentType() &&
   //         "Can't ask whether a dependent type is complete");
 
-  // We lock in the inheritance model once somebody has asked us to ensure
-  // that a pointer-to-member type is complete.
-  if (Context.getTargetInfo().getCXXABI().isMicrosoft()) {
-    if (const MemberPointerType *MPTy = T->getAs<MemberPointerType>()) {
-      if (!MPTy->getClass()->isDependentType()) {
+  if (const MemberPointerType *MPTy = T->getAs<MemberPointerType>()) {
+    if (!MPTy->getClass()->isDependentType()) {
+      if (getLangOpts().CompleteMemberPointers &&
+          !MPTy->getClass()->getAsCXXRecordDecl()->isBeingDefined() &&
+          RequireCompleteType(Loc, QualType(MPTy->getClass(), 0),
+                              diag::err_memptr_incomplete))
+        return true;
+
+      // We lock in the inheritance model once somebody has asked us to ensure
+      // that a pointer-to-member type is complete.
+      if (Context.getTargetInfo().getCXXABI().isMicrosoft()) {
         (void)isCompleteType(Loc, QualType(MPTy->getClass(), 0));
         assignInheritanceModel(*this, MPTy->getMostRecentCXXRecordDecl());
       }