================ @@ -1052,11 +1053,143 @@ CodeGenFunction::emitFlexibleArrayMemberSize(const Expr *E, unsigned Type, return Builder.CreateSelect(Cmp, Res, ConstantInt::get(ResType, 0, IsSigned)); } +namespace { + +/// SubobjectFinder - A simple visitor to find the "sub-object" pointed to by a +/// __builtin_dynamic_object_size call. Information gathered from the +/// sub-object is used by the back-end to determine the correct size when the +/// 'TYPE' of the __bdos call has the least significant bit set (i.e. asking +/// for the sub-object size). +/// +/// The expectation is that we'll eventually hit one of three expression types: +/// +/// 1. DeclRefExpr - This is the expression for the base of the structure. +/// 2. MemberExpr - This is the field in the structure. +/// 3. CompoundLiteralExpr - This is for people who create something +/// heretical like (struct foo has a flexible array member): +/// +/// (struct foo){ 1, 2 }.blah[idx]; +/// +/// All other expressions can be correctly handled with the current code. +struct SubobjectFinder + : public ConstStmtVisitor<SubobjectFinder, const Expr *> { + SubobjectFinder() = default; + + //===--------------------------------------------------------------------===// + // Visitor Methods + //===--------------------------------------------------------------------===// + + const Expr *VisitStmt(const Stmt *S) { return nullptr; } + + const Expr *VisitDeclRefExpr(const DeclRefExpr *E) { return E; } + const Expr *VisitMemberExpr(const MemberExpr *E) { return E; } + const Expr *VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) { + return E; + } + + const Expr *VisitArraySubscriptExpr(const ArraySubscriptExpr *E) { + return Visit(E->getBase()); + } + const Expr *VisitCastExpr(const CastExpr *E) { + return Visit(E->getSubExpr()); + } + const Expr *VisitParenExpr(const ParenExpr *E) { + return Visit(E->getSubExpr()); + } + const Expr *VisitUnaryAddrOf(const clang::UnaryOperator *E) { + return Visit(E->getSubExpr()); + } + const Expr *VisitUnaryDeref(const clang::UnaryOperator *E) { + return Visit(E->getSubExpr()); + } ---------------- zygoloid wrote:
I think you'll need to be more careful when walking through address-of / dereferences -- the set of things you should step over when traversing a pointer to an object is different from the set of things you should step over when traversing an object lvalue. For example, the bounds to use for `*p->member` will be computed as the bounds of `member`, which isn't correct. I think you could address this by either having separate traversals for pointers versus lvalues, or by avoiding (for example) stepping through lvalue-to-rvalue conversions when stepping over `CastExpr`s -- and in fact, the latter seems like a good idea in general, given that a `CastExpr` could do pretty much anything to the pointer / lvalue. In general, I think it's only really safe to step over casts that are a no-op for address purposes. Bitcasts seem OK, address space conversions seem OK, etc. but a lot of cast kinds are not going to be reasonable to step over. https://github.com/llvm/llvm-project/pull/83204 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits