1 //=== BuiltinFunctionChecker.cpp --------------------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This checker evaluates clang builtin functions.
12 //===----------------------------------------------------------------------===//
14 #include "ClangSACheckers.h"
15 #include "clang/Basic/Builtins.h"
16 #include "clang/StaticAnalyzer/Core/Checker.h"
17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20 using namespace clang;
25 class BuiltinFunctionChecker : public Checker<eval::Call> {
27 bool evalCall(const CallExpr *CE, CheckerContext &C) const;
32 bool BuiltinFunctionChecker::evalCall(const CallExpr *CE,
33 CheckerContext &C) const {
34 ProgramStateRef state = C.getState();
35 const FunctionDecl *FD = C.getCalleeDecl(CE);
36 const LocationContext *LCtx = C.getLocationContext();
40 switch (FD->getBuiltinID()) {
44 case Builtin::BI__builtin_assume: {
45 assert (CE->arg_begin() != CE->arg_end());
46 SVal ArgSVal = state->getSVal(CE->getArg(0), LCtx);
47 if (ArgSVal.isUndef())
48 return true; // Return true to model purity.
50 state = state->assume(ArgSVal.castAs<DefinedOrUnknownSVal>(), true);
51 // FIXME: do we want to warn here? Not right now. The most reports might
52 // come from infeasible paths, thus being false positives.
56 C.addTransition(state);
60 case Builtin::BI__builtin_unpredictable:
61 case Builtin::BI__builtin_expect:
62 case Builtin::BI__builtin_assume_aligned:
63 case Builtin::BI__builtin_addressof: {
64 // For __builtin_unpredictable, __builtin_expect, and
65 // __builtin_assume_aligned, just return the value of the subexpression.
66 // __builtin_addressof is going from a reference to a pointer, but those
67 // are represented the same way in the analyzer.
68 assert (CE->arg_begin() != CE->arg_end());
69 SVal X = state->getSVal(*(CE->arg_begin()), LCtx);
70 C.addTransition(state->BindExpr(CE, LCtx, X));
74 case Builtin::BI__builtin_alloca_with_align:
75 case Builtin::BI__builtin_alloca: {
76 // FIXME: Refactor into StoreManager itself?
77 MemRegionManager& RM = C.getStoreManager().getRegionManager();
78 const AllocaRegion* R =
79 RM.getAllocaRegion(CE, C.blockCount(), C.getLocationContext());
81 // Set the extent of the region in bytes. This enables us to use the
82 // SVal of the argument directly. If we save the extent in bits, we
83 // cannot represent values like symbol*8.
84 DefinedOrUnknownSVal Size =
85 state->getSVal(*(CE->arg_begin()), LCtx).castAs<DefinedOrUnknownSVal>();
87 SValBuilder& svalBuilder = C.getSValBuilder();
88 DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
89 DefinedOrUnknownSVal extentMatchesSizeArg =
90 svalBuilder.evalEQ(state, Extent, Size);
91 state = state->assume(extentMatchesSizeArg, true);
92 assert(state && "The region should not have any previous constraints");
94 C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R)));
98 case Builtin::BI__builtin_object_size: {
99 // This must be resolvable at compile time, so we defer to the constant
100 // evaluator for a value.
101 SVal V = UnknownVal();
103 if (CE->EvaluateAsInt(Result, C.getASTContext(), Expr::SE_NoSideEffects)) {
104 // Make sure the result has the correct type.
105 SValBuilder &SVB = C.getSValBuilder();
106 BasicValueFactory &BVF = SVB.getBasicValueFactory();
107 BVF.getAPSIntType(CE->getType()).apply(Result);
108 V = SVB.makeIntVal(Result);
111 C.addTransition(state->BindExpr(CE, LCtx, V));
117 void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) {
118 mgr.registerChecker<BuiltinFunctionChecker>();