[analyzer] Correct modelling of OSDynamicCast: eagerly state split
Previously, OSDynamicCast was modeled as an identity.
This is not correct: the output of OSDynamicCast may be zero even if the
input was not zero (if the class is not of desired type), and thus the
modeling led to false positives.
Instead, we are doing eager state split:
in one branch, the returned value is identical to the input parameter,
and in the other branch, the returned value is zero.
This patch required a substantial refactoring of canEval infrastructure,
as now it can return different function summaries, and not just true/false.
rdar://45497400
Differential Revision: https://reviews.llvm.org/D53624
llvm-svn: 345338
diff --git a/clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.cpp
index 9826e1c..7db1465 100644
--- a/clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.cpp
@@ -774,14 +774,17 @@
const LocationContext *LCtx = C.getLocationContext();
+ using BehaviorSummary = RetainSummaryManager::BehaviorSummary;
+ Optional<BehaviorSummary> BSmr =
+ SmrMgr.canEval(CE, FD, hasTrustedImplementationAnnotation);
+
// See if it's one of the specific functions we know how to eval.
- if (!SmrMgr.canEval(CE, FD, hasTrustedImplementationAnnotation))
+ if (!BSmr)
return false;
// Bind the return value.
- // For now, all the functions which we can evaluate and which take
- // at least one argument are identities.
- if (CE->getNumArgs() >= 1) {
+ if (BSmr == BehaviorSummary::Identity ||
+ BSmr == BehaviorSummary::IdentityOrZero) {
SVal RetVal = state->getSVal(CE->getArg(0), LCtx);
// If the receiver is unknown or the function has
@@ -793,7 +796,24 @@
RetVal =
SVB.conjureSymbolVal(nullptr, CE, LCtx, ResultTy, C.blockCount());
}
- state = state->BindExpr(CE, LCtx, RetVal, false);
+ state = state->BindExpr(CE, LCtx, RetVal, /*Invalidate=*/false);
+
+ if (BSmr == BehaviorSummary::IdentityOrZero) {
+ // Add a branch where the output is zero.
+ ProgramStateRef NullOutputState = C.getState();
+
+ // Assume that output is zero on the other branch.
+ NullOutputState = NullOutputState->BindExpr(
+ CE, LCtx, C.getSValBuilder().makeNull(), /*Invalidate=*/false);
+
+ C.addTransition(NullOutputState);
+
+ // And on the original branch assume that both input and
+ // output are non-zero.
+ if (auto L = RetVal.getAs<DefinedOrUnknownSVal>())
+ state = state->assume(*L, /*Assumption=*/true);
+
+ }
}
C.addTransition(state);
diff --git a/clang/lib/StaticAnalyzer/Core/RetainSummaryManager.cpp b/clang/lib/StaticAnalyzer/Core/RetainSummaryManager.cpp
index 09b7442..e933326 100644
--- a/clang/lib/StaticAnalyzer/Core/RetainSummaryManager.cpp
+++ b/clang/lib/StaticAnalyzer/Core/RetainSummaryManager.cpp
@@ -65,6 +65,10 @@
return isSubclass(D, "OSObject");
}
+static bool isOSObjectDynamicCast(StringRef S) {
+ return S == "safeMetaCast";
+}
+
static bool isOSIteratorSubclass(const Decl *D) {
return isSubclass(D, "OSIterator");
}
@@ -231,6 +235,9 @@
if (TrackOSObjects && PD && isOSObjectSubclass(PD)) {
if (const IdentifierInfo *II = FD->getIdentifier()) {
+ if (isOSObjectDynamicCast(II->getName()))
+ return getDefaultSummary();
+
// All objects returned with functions starting with "get" are getters.
if (II->getName().startswith("get")) {
@@ -515,20 +522,21 @@
return hasRCAnnotation(FD, "rc_ownership_trusted_implementation");
}
-bool RetainSummaryManager::canEval(const CallExpr *CE,
- const FunctionDecl *FD,
- bool &hasTrustedImplementationAnnotation) {
+Optional<RetainSummaryManager::BehaviorSummary>
+RetainSummaryManager::canEval(const CallExpr *CE, const FunctionDecl *FD,
+ bool &hasTrustedImplementationAnnotation) {
IdentifierInfo *II = FD->getIdentifier();
if (!II)
- return false;
+ return None;
StringRef FName = II->getName();
FName = FName.substr(FName.find_first_not_of('_'));
QualType ResultTy = CE->getCallReturnType(Ctx);
if (ResultTy->isObjCIdType()) {
- return II->isStr("NSMakeCollectable");
+ if (II->isStr("NSMakeCollectable"))
+ return BehaviorSummary::Identity;
} else if (ResultTy->isPointerType()) {
// Handle: (CF|CG|CV)Retain
// CFAutorelease
@@ -536,31 +544,34 @@
if (cocoa::isRefType(ResultTy, "CF", FName) ||
cocoa::isRefType(ResultTy, "CG", FName) ||
cocoa::isRefType(ResultTy, "CV", FName))
- return isRetain(FD, FName) || isAutorelease(FD, FName) ||
- isMakeCollectable(FName);
+ if (isRetain(FD, FName) || isAutorelease(FD, FName) ||
+ isMakeCollectable(FName))
+ return BehaviorSummary::Identity;
- // Process OSDynamicCast: should just return the first argument.
- // For now, treating the cast as a no-op, and disregarding the case where
- // the output becomes null due to the type mismatch.
- if (TrackOSObjects && FName == "safeMetaCast") {
- return true;
+ // safeMetaCast is called by OSDynamicCast.
+ // We assume that OSDynamicCast is either an identity (cast is OK,
+ // the input was non-zero),
+ // or that it returns zero (when the cast failed, or the input
+ // was zero).
+ if (TrackOSObjects && isOSObjectDynamicCast(FName)) {
+ return BehaviorSummary::IdentityOrZero;
}
const FunctionDecl* FDD = FD->getDefinition();
if (FDD && isTrustedReferenceCountImplementation(FDD)) {
hasTrustedImplementationAnnotation = true;
- return true;
+ return BehaviorSummary::Identity;
}
}
if (const auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
const CXXRecordDecl *Parent = MD->getParent();
if (TrackOSObjects && Parent && isOSObjectSubclass(Parent))
- return FName == "release" || FName == "retain";
+ if (FName == "release" || FName == "retain")
+ return BehaviorSummary::NoOp;
}
- return false;
-
+ return None;
}
const RetainSummary *