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      1 //===--- AttrNonNullChecker.h - Undefined arguments checker ----*- 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 defines AttrNonNullChecker, a builtin check in ExprEngine that
     11 // performs checks for arguments declared to have nonnull attribute.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #include "ClangSACheckers.h"
     16 #include "clang/StaticAnalyzer/Core/Checker.h"
     17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
     18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
     19 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
     20 
     21 using namespace clang;
     22 using namespace ento;
     23 
     24 namespace {
     25 class AttrNonNullChecker
     26   : public Checker< check::PreStmt<CallExpr> > {
     27   mutable llvm::OwningPtr<BugType> BT;
     28 public:
     29 
     30   void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
     31 };
     32 } // end anonymous namespace
     33 
     34 void AttrNonNullChecker::checkPreStmt(const CallExpr *CE,
     35                                       CheckerContext &C) const {
     36   const ProgramState *state = C.getState();
     37 
     38   // Check if the callee has a 'nonnull' attribute.
     39   SVal X = state->getSVal(CE->getCallee());
     40 
     41   const FunctionDecl *FD = X.getAsFunctionDecl();
     42   if (!FD)
     43     return;
     44 
     45   const NonNullAttr* Att = FD->getAttr<NonNullAttr>();
     46   if (!Att)
     47     return;
     48 
     49   // Iterate through the arguments of CE and check them for null.
     50   unsigned idx = 0;
     51 
     52   for (CallExpr::const_arg_iterator I=CE->arg_begin(), E=CE->arg_end(); I!=E;
     53        ++I, ++idx) {
     54 
     55     if (!Att->isNonNull(idx))
     56       continue;
     57 
     58     SVal V = state->getSVal(*I);
     59     DefinedSVal *DV = dyn_cast<DefinedSVal>(&V);
     60 
     61     // If the value is unknown or undefined, we can't perform this check.
     62     if (!DV)
     63       continue;
     64 
     65     if (!isa<Loc>(*DV)) {
     66       // If the argument is a union type, we want to handle a potential
     67       // transparent_unoin GCC extension.
     68       QualType T = (*I)->getType();
     69       const RecordType *UT = T->getAsUnionType();
     70       if (!UT || !UT->getDecl()->hasAttr<TransparentUnionAttr>())
     71         continue;
     72       if (nonloc::CompoundVal *CSV = dyn_cast<nonloc::CompoundVal>(DV)) {
     73         nonloc::CompoundVal::iterator CSV_I = CSV->begin();
     74         assert(CSV_I != CSV->end());
     75         V = *CSV_I;
     76         DV = dyn_cast<DefinedSVal>(&V);
     77         assert(++CSV_I == CSV->end());
     78         if (!DV)
     79           continue;
     80       }
     81       else {
     82         // FIXME: Handle LazyCompoundVals?
     83         continue;
     84       }
     85     }
     86 
     87     ConstraintManager &CM = C.getConstraintManager();
     88     const ProgramState *stateNotNull, *stateNull;
     89     llvm::tie(stateNotNull, stateNull) = CM.assumeDual(state, *DV);
     90 
     91     if (stateNull && !stateNotNull) {
     92       // Generate an error node.  Check for a null node in case
     93       // we cache out.
     94       if (ExplodedNode *errorNode = C.generateSink(stateNull)) {
     95 
     96         // Lazily allocate the BugType object if it hasn't already been
     97         // created. Ownership is transferred to the BugReporter object once
     98         // the BugReport is passed to 'EmitWarning'.
     99         if (!BT)
    100           BT.reset(new BugType("Argument with 'nonnull' attribute passed null",
    101                                "API"));
    102 
    103         BugReport *R =
    104           new BugReport(*BT, "Null pointer passed as an argument to a "
    105                              "'nonnull' parameter", errorNode);
    106 
    107         // Highlight the range of the argument that was null.
    108         const Expr *arg = *I;
    109         R->addRange(arg->getSourceRange());
    110         R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(errorNode,
    111                                                                    arg));
    112         // Emit the bug report.
    113         C.EmitReport(R);
    114       }
    115 
    116       // Always return.  Either we cached out or we just emitted an error.
    117       return;
    118     }
    119 
    120     // If a pointer value passed the check we should assume that it is
    121     // indeed not null from this point forward.
    122     assert(stateNotNull);
    123     state = stateNotNull;
    124   }
    125 
    126   // If we reach here all of the arguments passed the nonnull check.
    127   // If 'state' has been updated generated a new node.
    128   C.addTransition(state);
    129 }
    130 
    131 void ento::registerAttrNonNullChecker(CheckerManager &mgr) {
    132   mgr.registerChecker<AttrNonNullChecker>();
    133 }
    134