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//=== BuiltinFunctionChecker.cpp --------------------------------*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This checker evaluates clang builtin functions.
#include "ClangSACheckers.h"
#include "clang/Basic/Builtins.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
using namespace clang;
using namespace ento;
namespace {
class BuiltinFunctionChecker : public Checker<eval::Call> {
bool evalCall(const CallExpr *CE, CheckerContext &C) const;
bool BuiltinFunctionChecker::evalCall(const CallExpr *CE,
CheckerContext &C) const {
ProgramStateRef state = C.getState();
const FunctionDecl *FD = C.getCalleeDecl(CE);
const LocationContext *LCtx = C.getLocationContext();
if (!FD)
return false;
switch (FD->getBuiltinID()) {
return false;
case Builtin::BI__builtin_assume: {
assert (CE->arg_begin() != CE->arg_end());
SVal ArgSVal = C.getSVal(CE->getArg(0));
if (ArgSVal.isUndef())
return true; // Return true to model purity.
state = state->assume(ArgSVal.castAs<DefinedOrUnknownSVal>(), true);
// FIXME: do we want to warn here? Not right now. The most reports might
// come from infeasible paths, thus being false positives.
if (!state) {
C.generateSink(C.getState(), C.getPredecessor());
return true;
return true;
case Builtin::BI__builtin_unpredictable:
case Builtin::BI__builtin_expect:
case Builtin::BI__builtin_assume_aligned:
case Builtin::BI__builtin_addressof: {
// For __builtin_unpredictable, __builtin_expect, and
// __builtin_assume_aligned, just return the value of the subexpression.
// __builtin_addressof is going from a reference to a pointer, but those
// are represented the same way in the analyzer.
assert (CE->arg_begin() != CE->arg_end());
SVal X = C.getSVal(*(CE->arg_begin()));
C.addTransition(state->BindExpr(CE, LCtx, X));
return true;
case Builtin::BI__builtin_alloca_with_align:
case Builtin::BI__builtin_alloca: {
// FIXME: Refactor into StoreManager itself?
MemRegionManager& RM = C.getStoreManager().getRegionManager();
const AllocaRegion* R =
RM.getAllocaRegion(CE, C.blockCount(), C.getLocationContext());
// Set the extent of the region in bytes. This enables us to use the
// SVal of the argument directly. If we save the extent in bits, we
// cannot represent values like symbol*8.
auto Size = C.getSVal(*(CE->arg_begin())).castAs<DefinedOrUnknownSVal>();
SValBuilder& svalBuilder = C.getSValBuilder();
DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
DefinedOrUnknownSVal extentMatchesSizeArg =
svalBuilder.evalEQ(state, Extent, Size);
state = state->assume(extentMatchesSizeArg, true);
assert(state && "The region should not have any previous constraints");
C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R)));
return true;
case Builtin::BI__builtin_object_size:
case Builtin::BI__builtin_constant_p: {
// This must be resolvable at compile time, so we defer to the constant
// evaluator for a value.
SVal V = UnknownVal();
llvm::APSInt Result;
if (CE->EvaluateAsInt(Result, C.getASTContext(), Expr::SE_NoSideEffects)) {
// Make sure the result has the correct type.
SValBuilder &SVB = C.getSValBuilder();
BasicValueFactory &BVF = SVB.getBasicValueFactory();
V = SVB.makeIntVal(Result);
C.addTransition(state->BindExpr(CE, LCtx, V));
return true;
void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) {