AST: Don't assume two zero sized objects live at different addresses
Zero sized objects may overlap with each other or any other object.
This fixes PR21786.
llvm-svn: 223852
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 2891338..acf78ef 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -1422,6 +1422,12 @@
return Decl && Decl->isWeak();
}
+static bool isZeroSized(const LValue &Value) {
+ const ValueDecl *Decl = GetLValueBaseDecl(Value);
+ return Decl && isa<VarDecl>(Decl) &&
+ Decl->getASTContext().getTypeSize(Decl->getType()) == 0;
+}
+
static bool EvalPointerValueAsBool(const APValue &Value, bool &Result) {
// A null base expression indicates a null pointer. These are always
// evaluatable, and they are false unless the offset is zero.
@@ -6979,6 +6985,10 @@
(RHSValue.Base && RHSValue.Offset.isZero() &&
isOnePastTheEndOfCompleteObject(Info.Ctx, LHSValue)))
return Error(E);
+ // We can't tell whether an object is at the same address as another
+ // zero sized object.
+ if (isZeroSized(LHSValue) || isZeroSized(RHSValue))
+ return Error(E);
// Pointers with different bases cannot represent the same object.
// (Note that clang defaults to -fmerge-all-constants, which can
// lead to inconsistent results for comparisons involving the address