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/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"
19
20using namespace clang;
21using namespace ento;
22
23namespace {
24
25class BuiltinFunctionChecker : public Checker<eval::Call> {
26public:
27  bool evalCall(const CallExpr *CE, CheckerContext &C) const;
28};
29
30}
31
32bool 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  switch (FD->getBuiltinID()) {
41  default:
42    return false;
43
44  case Builtin::BI__builtin_expect:
45  case Builtin::BI__builtin_addressof: {
46    // For __builtin_expect, just return the value of the subexpression.
47    // __builtin_addressof is going from a reference to a pointer, but those
48    // are represented the same way in the analyzer.
49    assert (CE->arg_begin() != CE->arg_end());
50    SVal X = state->getSVal(*(CE->arg_begin()), LCtx);
51    C.addTransition(state->BindExpr(CE, LCtx, X));
52    return true;
53  }
54
55  case Builtin::BI__builtin_alloca: {
56    // FIXME: Refactor into StoreManager itself?
57    MemRegionManager& RM = C.getStoreManager().getRegionManager();
58    const AllocaRegion* R =
59      RM.getAllocaRegion(CE, C.blockCount(), C.getLocationContext());
60
61    // Set the extent of the region in bytes. This enables us to use the
62    // SVal of the argument directly. If we save the extent in bits, we
63    // cannot represent values like symbol*8.
64    DefinedOrUnknownSVal Size =
65        state->getSVal(*(CE->arg_begin()), LCtx).castAs<DefinedOrUnknownSVal>();
66
67    SValBuilder& svalBuilder = C.getSValBuilder();
68    DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
69    DefinedOrUnknownSVal extentMatchesSizeArg =
70      svalBuilder.evalEQ(state, Extent, Size);
71    state = state->assume(extentMatchesSizeArg, true);
72    assert(state && "The region should not have any previous constraints");
73
74    C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R)));
75    return true;
76  }
77
78  case Builtin::BI__builtin_object_size: {
79    // This must be resolvable at compile time, so we defer to the constant
80    // evaluator for a value.
81    SVal V = UnknownVal();
82    llvm::APSInt Result;
83    if (CE->EvaluateAsInt(Result, C.getASTContext(), Expr::SE_NoSideEffects)) {
84      // Make sure the result has the correct type.
85      SValBuilder &SVB = C.getSValBuilder();
86      BasicValueFactory &BVF = SVB.getBasicValueFactory();
87      BVF.getAPSIntType(CE->getType()).apply(Result);
88      V = SVB.makeIntVal(Result);
89    }
90
91    C.addTransition(state->BindExpr(CE, LCtx, V));
92    return true;
93  }
94  }
95}
96
97void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) {
98  mgr.registerChecker<BuiltinFunctionChecker>();
99}
100