Add an attribute to forbid temporary instances of a type. This allows class

authors to write 

  class __attribute__((forbid_temporaries)) Name { ... };

when they want to force users to name all variables of the type. This protects
people from doing things like creating a scoped_lock that only lives for a
single statement instead of an entire scope.

The warning produced by this attribute can be disabled by
-Wno-forbid-temporaries.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@124217 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 1 deletions

diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index 0b7a051365..cb02be546e 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -3188,9 +3188,12 @@ ExprResult Sema::MaybeBindToTemporary(Expr *E) {
     }
   }
 
+  CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
+  if (RD->getAttr<ForbidTemporariesAttr>())
+    Diag(E->getExprLoc(), diag::warn_temporaries_forbidden) << E->getType();
+
   // That should be enough to guarantee that this type is complete.
   // If it has a trivial destructor, we can avoid the extra copy.
-  CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
   if (RD->isInvalidDecl() || RD->hasTrivialDestructor())
     return Owned(E);