Sema, CodeGen: Ensure that an implicit copy ctor is available more often under the Microsoft C++ ABI.

This is needed because whether the constructor is deleted can control whether
we pass structs by value directly.

To fix this properly we probably want a more direct way for CodeGen to ask
whether the constructor was deleted.

Fixes PR31049.

Differential Revision: https://reviews.llvm.org/D26822

llvm-svn: 287600

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 82da95e9a67..7d208a43ada 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -7396,6 +7396,17 @@ void Sema::AddImplicitlyDeclaredMembersToClass(CXXRecordDecl *ClassDecl) {
     if (ClassDecl->needsOverloadResolutionForCopyConstructor() ||
         ClassDecl->hasInheritedConstructor())
       DeclareImplicitCopyConstructor(ClassDecl);
+    // For the MS ABI we need to know whether the copy ctor is deleted. A
+    // prerequisite for deleting the implicit copy ctor is that the class has a
+    // move ctor or move assignment that is either user-declared or whose
+    // semantics are inherited from a subobject. FIXME: We should provide a more
+    // direct way for CodeGen to ask whether the constructor was deleted.
+    else if (Context.getTargetInfo().getCXXABI().isMicrosoft() &&
+             (ClassDecl->hasUserDeclaredMoveConstructor() ||
+              ClassDecl->needsOverloadResolutionForMoveConstructor() ||
+              ClassDecl->hasUserDeclaredMoveAssignment() ||
+              ClassDecl->needsOverloadResolutionForMoveAssignment()))
+      DeclareImplicitCopyConstructor(ClassDecl);
   }
 
   if (getLangOpts().CPlusPlus11 && ClassDecl->needsImplicitMoveConstructor()) {