d6d84b5d14
This commit ensures that the `CallDescription`s in `MallocChecker` are matched with the mode `CDM::CLibrary`, so: - they don't match methods or functions within user-defined namespaces; - they also match builtin variants of these functions (if any), so the checker can model `__builtin_alloca()` like `alloca()`. This change fixes https://github.com/llvm/llvm-project/issues/81597. New tests were added to verify that `std::malloc` and `std::free` (from `<cstdlib>`) are modeled, but a method that's named e.g. `free` isn't confused with the memory release function. The responsibility for modeling `__builtin_alloca` and `__builtin_alloca_with_align` was moved from `BuiltinFunctionChecker` to `MallocChecker`, to avoid buggy interactions between the checkers and ensure that the builtin and non-builtin variants are handled by exactly the same logic. This change might be a step backwards for the users who don't have `unix.Malloc` enabled; but I suspect that `__builtin_alloca()` is so rare that it would be a waste of time to implement backwards compatibility for them. There were several test files that relied on `__builtin_alloca()` calls to get an `AllocaRegion`, these were modified to enable `unix.Malloc`. One of these files (cxx-uninitialized-object-ptr-ref.cpp) had some tests that relied on the fact that `malloc()` was treated as a "black box" in them, these were updated to use `calloc()` (to get initialized memory) and `free()` (to avoid memory leak reports). While I was developing this change, I found a very suspicious assert in `MallocChecker`. As it isn't blocking the goals of this commit, I just marked it with a FIXME, but I'll try to investigate and fix it in a follow-up change.
124 lines
4.3 KiB
C++
124 lines
4.3 KiB
C++
//=== BuiltinFunctionChecker.cpp --------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This checker evaluates "standalone" clang builtin functions that are not
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// just special-cased variants of well-known non-builtin functions.
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// Builtin functions like __builtin_memcpy and __builtin_alloca should be
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// evaluated by the same checker that handles their non-builtin variant to
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// ensure that the two variants are handled consistently.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/Basic/Builtins.h"
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#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h"
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using namespace clang;
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using namespace ento;
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namespace {
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class BuiltinFunctionChecker : public Checker<eval::Call> {
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public:
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bool evalCall(const CallEvent &Call, CheckerContext &C) const;
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};
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}
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bool BuiltinFunctionChecker::evalCall(const CallEvent &Call,
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CheckerContext &C) const {
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ProgramStateRef state = C.getState();
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const auto *FD = dyn_cast_or_null<FunctionDecl>(Call.getDecl());
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if (!FD)
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return false;
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const LocationContext *LCtx = C.getLocationContext();
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const Expr *CE = Call.getOriginExpr();
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switch (FD->getBuiltinID()) {
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default:
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return false;
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case Builtin::BI__builtin_assume:
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case Builtin::BI__assume: {
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assert (Call.getNumArgs() > 0);
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SVal Arg = Call.getArgSVal(0);
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if (Arg.isUndef())
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return true; // Return true to model purity.
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state = state->assume(Arg.castAs<DefinedOrUnknownSVal>(), true);
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// FIXME: do we want to warn here? Not right now. The most reports might
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// come from infeasible paths, thus being false positives.
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if (!state) {
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C.generateSink(C.getState(), C.getPredecessor());
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return true;
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}
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C.addTransition(state);
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return true;
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}
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case Builtin::BI__builtin_unpredictable:
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case Builtin::BI__builtin_expect:
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case Builtin::BI__builtin_expect_with_probability:
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case Builtin::BI__builtin_assume_aligned:
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case Builtin::BI__builtin_addressof:
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case Builtin::BI__builtin_function_start: {
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// For __builtin_unpredictable, __builtin_expect,
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// __builtin_expect_with_probability and __builtin_assume_aligned,
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// just return the value of the subexpression.
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// __builtin_addressof is going from a reference to a pointer, but those
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// are represented the same way in the analyzer.
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assert (Call.getNumArgs() > 0);
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SVal Arg = Call.getArgSVal(0);
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C.addTransition(state->BindExpr(CE, LCtx, Arg));
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return true;
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}
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case Builtin::BI__builtin_dynamic_object_size:
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case Builtin::BI__builtin_object_size:
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case Builtin::BI__builtin_constant_p: {
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// This must be resolvable at compile time, so we defer to the constant
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// evaluator for a value.
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SValBuilder &SVB = C.getSValBuilder();
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SVal V = UnknownVal();
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Expr::EvalResult EVResult;
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if (CE->EvaluateAsInt(EVResult, C.getASTContext(), Expr::SE_NoSideEffects)) {
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// Make sure the result has the correct type.
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llvm::APSInt Result = EVResult.Val.getInt();
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BasicValueFactory &BVF = SVB.getBasicValueFactory();
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BVF.getAPSIntType(CE->getType()).apply(Result);
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V = SVB.makeIntVal(Result);
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}
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if (FD->getBuiltinID() == Builtin::BI__builtin_constant_p) {
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// If we didn't manage to figure out if the value is constant or not,
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// it is safe to assume that it's not constant and unsafe to assume
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// that it's constant.
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if (V.isUnknown())
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V = SVB.makeIntVal(0, CE->getType());
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}
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C.addTransition(state->BindExpr(CE, LCtx, V));
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return true;
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}
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}
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}
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void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) {
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mgr.registerChecker<BuiltinFunctionChecker>();
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}
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bool ento::shouldRegisterBuiltinFunctionChecker(const CheckerManager &mgr) {
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return true;
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}
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