From 2850376184b7e7aa81b5034ba44b001f8c55e07a Mon Sep 17 00:00:00 2001 From: Eli Friedman Date: Mon, 16 Apr 2012 19:23:57 +0000 Subject: [PATCH] Per Richard's comments on r154794, add the checks necessary to handle constant-folding relational comparisons safely in case the user is using -fwrapv or equivalent. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154849 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/AST/ExprConstant.cpp | 15 +++++++++++++-- test/Sema/const-eval.c | 6 ++++++ 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp index 4839c29976..66a88b065c 100644 --- a/lib/AST/ExprConstant.cpp +++ b/lib/AST/ExprConstant.cpp @@ -5090,8 +5090,6 @@ bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) { // The comparison here must be unsigned, and performed with the same // width as the pointer. - // FIXME: Knowing the base is the same for the LHS and RHS isn't enough - // for relational operators. unsigned PtrSize = Info.Ctx.getTypeSize(LHSTy); uint64_t CompareLHS = LHSOffset.getQuantity(); uint64_t CompareRHS = RHSOffset.getQuantity(); @@ -5100,6 +5098,19 @@ bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) { CompareLHS &= Mask; CompareRHS &= Mask; + // If there is a base and this is a relational operator, we can only + // compare pointers within the object in question; otherwise, the result + // depends on where the object is located in memory. + if (!LHSValue.Base.isNull() && E->isRelationalOp()) { + QualType BaseTy = getType(LHSValue.Base); + if (BaseTy->isIncompleteType()) + return Error(E); + CharUnits Size = Info.Ctx.getTypeSizeInChars(BaseTy); + uint64_t OffsetLimit = Size.getQuantity(); + if (CompareLHS > OffsetLimit || CompareRHS > OffsetLimit) + return Error(E); + } + switch (E->getOpcode()) { default: llvm_unreachable("missing comparison operator"); case BO_LT: return Success(CompareLHS < CompareRHS, E); diff --git a/test/Sema/const-eval.c b/test/Sema/const-eval.c index 3894d73d60..bc8b227ac8 100644 --- a/test/Sema/const-eval.c +++ b/test/Sema/const-eval.c @@ -125,3 +125,9 @@ EVAL_EXPR(44, "x"[0]); // expected-error {{variable length array}} // EVAL_EXPR(45, ((char*)-1) + 1 == 0 ? 1 : -1) EVAL_EXPR(46, ((char*)-1) + 1 < (char*) -1 ? 1 : -1) +EVAL_EXPR(47, &x < &x + 1 ? 1 : -1) +EVAL_EXPR(48, &x != &x - 1 ? 1 : -1) +EVAL_EXPR(49, &x < &x - 100 ? 1 : -1) // expected-error {{must have a constant size}} + +extern struct Test50S Test50; +EVAL_EXPR(50, &Test50 < (struct Test50S*)((unsigned)&Test50 + 10)) // expected-error {{must have a constant size}} -- 2.40.0