================
@@ -247,45 +240,134 @@ void StackAddrEscapeChecker::checkPreCall(const
CallEvent &Call,
}
}
-void StackAddrEscapeChecker::checkPreStmt(const ReturnStmt *RS,
- CheckerContext &C) const {
- if (!ChecksEnabled[CK_StackAddrEscapeChecker])
- return;
+/// A visitor made for use with a ScanReachableSymbols scanner, used
+/// for finding stack regions within an SVal that live on the current
+/// stack frame of the given checker context. This visitor excludes
+/// NonParamVarRegion that data is bound to in a BlockDataRegion's
+/// bindings, since these are likely uninteresting, e.g., in case a
+/// temporary is constructed on the stack, but it captures values
+/// that would leak.
+class FindStackRegionsSymbolVisitor final : public SymbolVisitor {
+ CheckerContext &Ctxt;
+ const StackFrameContext *StackFrameContext;
+ SmallVector<const MemRegion *> &EscapingStackRegions;
- const Expr *RetE = RS->getRetValue();
- if (!RetE)
- return;
- RetE = RetE->IgnoreParens();
+public:
+ explicit FindStackRegionsSymbolVisitor(
+ CheckerContext &Ctxt,
+ SmallVector<const MemRegion *> &StorageForStackRegions)
+ : Ctxt(Ctxt), StackFrameContext(Ctxt.getStackFrame()),
+ EscapingStackRegions(StorageForStackRegions) {}
- SVal V = C.getSVal(RetE);
- const MemRegion *R = V.getAsRegion();
- if (!R)
- return;
+ bool VisitSymbol(SymbolRef sym) override { return true; }
- if (const BlockDataRegion *B = dyn_cast<BlockDataRegion>(R))
- checkReturnedBlockCaptures(*B, C);
+ bool VisitMemRegion(const MemRegion *MR) override {
+ SaveIfEscapes(MR);
- if (!isa<StackSpaceRegion>(R->getMemorySpace()) || isNotInCurrentFrame(R, C))
- return;
+ if (const BlockDataRegion *BDR = MR->getAs<BlockDataRegion>())
+ return VisitBlockDataRegionCaptures(BDR);
+
+ return true;
+ }
+
+private:
+ void SaveIfEscapes(const MemRegion *MR) {
+ const StackSpaceRegion *SSR =
+ MR->getMemorySpace()->getAs<StackSpaceRegion>();
+ if (SSR && SSR->getStackFrame() == StackFrameContext)
+ EscapingStackRegions.push_back(MR);
+ }
+
+ bool VisitBlockDataRegionCaptures(const BlockDataRegion *BDR) {
+ for (auto Var : BDR->referenced_vars()) {
+ SVal Val = Ctxt.getState()->getSVal(Var.getCapturedRegion());
+ const MemRegion *Region = Val.getAsRegion();
+ if (Region) {
+ SaveIfEscapes(Region);
+ VisitMemRegion(Region);
+ }
+ }
+
+ return false;
+ }
+};
+
+/// Given some memory regions that are flagged by
FindStackRegionsSymbolVisitor,
+/// this function filters out memory regions that are being returned that are
+/// likely not true leaks:
+/// 1. If returning a block data region that has stack memory space
+/// 2. If returning a constructed object that has stack memory space
+static SmallVector<const MemRegion *>
+FilterReturnExpressionLeaks(const SmallVector<const MemRegion *> &MaybeEscaped,
+ CheckerContext &C, const Expr *RetE, SVal &RetVal)
{
+
+ SmallVector<const MemRegion *> WillEscape;
+
+ const MemRegion *RetRegion = RetVal.getAsRegion();
// Returning a record by value is fine. (In this case, the returned
// expression will be a copy-constructor, possibly wrapped in an
// ExprWithCleanups node.)
if (const ExprWithCleanups *Cleanup = dyn_cast<ExprWithCleanups>(RetE))
RetE = Cleanup->getSubExpr();
- if (isa<CXXConstructExpr>(RetE) && RetE->getType()->isRecordType())
- return;
+ bool IsConstructExpr =
+ isa<CXXConstructExpr>(RetE) && RetE->getType()->isRecordType();
// The CK_CopyAndAutoreleaseBlockObject cast causes the block to be copied
// so the stack address is not escaping here.
+ bool IsCopyAndAutoreleaseBlockObj = false;
if (const auto *ICE = dyn_cast<ImplicitCastExpr>(RetE)) {
- if (isa<BlockDataRegion>(R) &&
- ICE->getCastKind() == CK_CopyAndAutoreleaseBlockObject) {
- return;
- }
+ IsCopyAndAutoreleaseBlockObj =
+ isa_and_nonnull<BlockDataRegion>(RetRegion) &&
+ ICE->getCastKind() == CK_CopyAndAutoreleaseBlockObject;
+ }
+
+ for (const MemRegion *MR : MaybeEscaped) {
+ if (RetRegion == MR && (IsCopyAndAutoreleaseBlockObj || IsConstructExpr))
+ continue;
+
+ // If this is a construct expr of an unelided return value copy, then don't
+ // warn about returning a region that currently lives on the stack.
+ if (IsConstructExpr && RetVal.getAs<nonloc::LazyCompoundVal>() &&
----------------
Flandini wrote:
This line is only for removing warnings. It is a little loose and maybe could
cause some false negatives. Is there a way here to relate the lazy compound val
that would be returned and the temp object region in an example like this from
copy-elision.cpp test:
```
template <typename T> struct AddressVector {
T *buf[20];
int len;
AddressVector() : len(0) {}
void push(T *t) {
buf[len] = t;
++len;
}
};
class ClassWithoutDestructor {
AddressVector<ClassWithoutDestructor> &v;
public:
ClassWithoutDestructor(AddressVector<ClassWithoutDestructor> &v) : v(v) {
push();
}
ClassWithoutDestructor(ClassWithoutDestructor &&c) : v(c.v) { push(); }
ClassWithoutDestructor(const ClassWithoutDestructor &c) : v(c.v) { push(); }
void push() { v.push(this); }
};
ClassWithoutDestructor make1(AddressVector<ClassWithoutDestructor> &v) {
return ClassWithoutDestructor(v);
// no-elide-warning@-1 {{Address of stack memory associated with temporary \
object of type 'ClassWithoutDestructor' is still \
referred to by the caller variable 'v' upon returning to the caller}}
}
```
Without some check like this, then the line with `return
ClassWithoutDestructor(v); ` will warn, and I think it should not under
`-analyzer-config elide-constructors=false -DNO_ELIDE_FLAG -std=c++11`. Is
there a better way to relate the lazy compound val of the return expr and the
temp object region that is created?
https://github.com/llvm/llvm-project/pull/125638
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