Add a new warning, -Wover-aligned, which detects attempts to use the default

allocator to construct an object which declares more alignment than the default
allocator actually provides. Fixes PR9527!

llvm-svn: 148857

1 files changed, 16 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index bea0954c6f0..919ef06957c 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -20,6 +20,7 @@
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/TemplateDeduction.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/CharUnits.h"
 #include "clang/AST/CXXInheritance.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/ExprCXX.h"
@@ -1104,6 +1105,21 @@ Sema::BuildCXXNew(SourceLocation StartLoc, bool UseGlobal,
       PlaceArgs = &AllPlaceArgs[0];
   }
 
+  // Warn if the type is over-aligned and is being allocated by global operator
+  // new.
+  if (OperatorNew &&
+      (OperatorNew->isImplicit() ||
+       getSourceManager().isInSystemHeader(OperatorNew->getLocStart()))) {
+    if (unsigned Align = Context.getPreferredTypeAlign(AllocType.getTypePtr())){
+      unsigned SuitableAlign = Context.getTargetInfo().getSuitableAlign();
+      if (Align > SuitableAlign)
+        Diag(StartLoc, diag::warn_overaligned_type)
+            << AllocType
+            << unsigned(Align / Context.getCharWidth())
+            << unsigned(SuitableAlign / Context.getCharWidth());
+    }
+  }
+
   bool Init = ConstructorLParen.isValid();
   // --- Choosing a constructor ---
   CXXConstructorDecl *Constructor = 0;