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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. 

llvm-svn: 154849
This commit is contained in:
Eli Friedman 2012-04-16 19:23:57 +00:00
parent 44d2497138
commit 2f5b7c542e
2 changed files with 19 additions and 2 deletions
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15
clang/lib/AST/ExprConstant.cpp
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@ -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);

6
clang/test/Sema/const-eval.c
View File

@ -125,3 +125,9 @@ EVAL_EXPR(44, "x"[0]); // expected-error {{variable length array}}
// <rdar://problem/10962435>
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}}