================
@@ -15383,6 +15383,36 @@ static void diagnoseDeprecatedCopyOperation(Sema &S,
CXXMethodDecl *CopyOp) {
}
}
+// A defaulted copy or move assignment operator for a union copies the object
+// representation as if by a memcpy, the same way the defaulted union copy
+// constructor does. The memberwise loops in DefineImplicitCopyAssignment and
+// DefineImplicitMoveAssignment skip union members, so the whole-object copy is
+// emitted here instead. Marks AssignOp invalid and returns false on failure.
+static bool buildUnionAssignmentCopy(Sema &S, SourceLocation Loc,
+ CXXRecordDecl *ClassDecl,
+ std::optional<RefBuilder> &ExplicitObject,
+ std::optional<DerefBuilder> &DerefThis,
+ const ExprBuilder &From,
+ CXXMethodDecl *AssignOp,
+ SmallVectorImpl<Stmt *> &Statements) {
+ ExprBuilder &To = ExplicitObject ? static_cast<ExprBuilder
&>(*ExplicitObject)
+ : static_cast<ExprBuilder &>(*DerefThis);
+
+ // Copying the object representation is correct even for a union that is not
+ // trivially copyable, so -Wnontrivial-memcall is a false positive here.
+ // Ignoring warnings rather than casting the arguments to void* keeps them
+ // typed, which preserves their address space.
+ IgnoreAllWarningDiagRAII IgnoreWarnings(S.Diags);
+ StmtResult Copy = buildMemcpyForAssignmentOp(
+ S, Loc, S.Context.getCanonicalTagType(ClassDecl), To, From);
+ if (Copy.isInvalid()) {
+ AssignOp->setInvalidDecl();
----------------
adams381 wrote:
There are two callers of this helper: `Sema::DefineImplicitCopyAssignment` and
`Sema::DefineImplicitMoveAssignment`. I can remove the helper, but that would
require code duplication at both call sites.
https://github.com/llvm/llvm-project/pull/206579
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