1 //=== BuiltinFunctionChecker.cpp --------------------------------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This checker evaluates clang builtin functions.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "ClangSACheckers.h"
15 #include "clang/StaticAnalyzer/Core/Checker.h"
16 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
17 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
18 #include "clang/Basic/Builtins.h"
19
20 using namespace clang;
21 using namespace ento;
22
23 namespace {
24
25 class BuiltinFunctionChecker : public Checker<eval::Call> {
26 public:
27 bool evalCall(const CallExpr *CE, CheckerContext &C) const;
28 };
29
30 }
31
evalCall(const CallExpr * CE,CheckerContext & C) const32 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();
37 if (!FD)
38 return false;
39
40 unsigned id = FD->getBuiltinID();
41
42 if (!id)
43 return false;
44
45 switch (id) {
46 case Builtin::BI__builtin_expect: {
47 // For __builtin_expect, just return the value of the subexpression.
48 assert (CE->arg_begin() != CE->arg_end());
49 SVal X = state->getSVal(*(CE->arg_begin()), LCtx);
50 C.addTransition(state->BindExpr(CE, LCtx, X));
51 return true;
52 }
53
54 case Builtin::BI__builtin_alloca: {
55 // FIXME: Refactor into StoreManager itself?
56 MemRegionManager& RM = C.getStoreManager().getRegionManager();
57 const AllocaRegion* R =
58 RM.getAllocaRegion(CE, C.blockCount(), C.getLocationContext());
59
60 // Set the extent of the region in bytes. This enables us to use the
61 // SVal of the argument directly. If we save the extent in bits, we
62 // cannot represent values like symbol*8.
63 DefinedOrUnknownSVal Size =
64 cast<DefinedOrUnknownSVal>(state->getSVal(*(CE->arg_begin()), LCtx));
65
66 SValBuilder& svalBuilder = C.getSValBuilder();
67 DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
68 DefinedOrUnknownSVal extentMatchesSizeArg =
69 svalBuilder.evalEQ(state, Extent, Size);
70 state = state->assume(extentMatchesSizeArg, true);
71
72 C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R)));
73 return true;
74 }
75 }
76
77 return false;
78 }
79
registerBuiltinFunctionChecker(CheckerManager & mgr)80 void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) {
81 mgr.registerChecker<BuiltinFunctionChecker>();
82 }
83