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      1 //=== NoReturnFunctionChecker.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 defines NoReturnFunctionChecker, which evaluates functions that do not
     11 // return to the caller.
     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/PathSensitive/ObjCMessage.h"
     20 #include "llvm/ADT/StringSwitch.h"
     21 #include <cstdarg>
     22 
     23 using namespace clang;
     24 using namespace ento;
     25 
     26 namespace {
     27 
     28 class NoReturnFunctionChecker : public Checker< check::PostStmt<CallExpr>,
     29                                                 check::PostObjCMessage > {
     30 public:
     31   void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
     32   void checkPostObjCMessage(const ObjCMessage &msg, CheckerContext &C) const;
     33 };
     34 
     35 }
     36 
     37 void NoReturnFunctionChecker::checkPostStmt(const CallExpr *CE,
     38                                             CheckerContext &C) const {
     39   ProgramStateRef state = C.getState();
     40   const Expr *Callee = CE->getCallee();
     41 
     42   bool BuildSinks = getFunctionExtInfo(Callee->getType()).getNoReturn();
     43 
     44   if (!BuildSinks) {
     45     SVal L = state->getSVal(Callee, C.getLocationContext());
     46     const FunctionDecl *FD = L.getAsFunctionDecl();
     47     if (!FD)
     48       return;
     49 
     50     if (FD->getAttr<AnalyzerNoReturnAttr>())
     51       BuildSinks = true;
     52     else if (const IdentifierInfo *II = FD->getIdentifier()) {
     53       // HACK: Some functions are not marked noreturn, and don't return.
     54       //  Here are a few hardwired ones.  If this takes too long, we can
     55       //  potentially cache these results.
     56       BuildSinks
     57         = llvm::StringSwitch<bool>(StringRef(II->getName()))
     58             .Case("exit", true)
     59             .Case("panic", true)
     60             .Case("error", true)
     61             .Case("Assert", true)
     62             // FIXME: This is just a wrapper around throwing an exception.
     63             //  Eventually inter-procedural analysis should handle this easily.
     64             .Case("ziperr", true)
     65             .Case("assfail", true)
     66             .Case("db_error", true)
     67             .Case("__assert", true)
     68             .Case("__assert_rtn", true)
     69             .Case("__assert_fail", true)
     70             .Case("dtrace_assfail", true)
     71             .Case("yy_fatal_error", true)
     72             .Case("_XCAssertionFailureHandler", true)
     73             .Case("_DTAssertionFailureHandler", true)
     74             .Case("_TSAssertionFailureHandler", true)
     75             .Default(false);
     76     }
     77   }
     78 
     79   if (BuildSinks)
     80     C.generateSink();
     81 }
     82 
     83 static bool END_WITH_NULL isMultiArgSelector(const Selector *Sel, ...) {
     84   va_list argp;
     85   va_start(argp, Sel);
     86 
     87   unsigned Slot = 0;
     88   const char *Arg;
     89   while ((Arg = va_arg(argp, const char *))) {
     90     if (!Sel->getNameForSlot(Slot).equals(Arg))
     91       break; // still need to va_end!
     92     ++Slot;
     93   }
     94 
     95   va_end(argp);
     96 
     97   // We only succeeded if we made it to the end of the argument list.
     98   return (Arg == NULL);
     99 }
    100 
    101 void NoReturnFunctionChecker::checkPostObjCMessage(const ObjCMessage &Msg,
    102                                                    CheckerContext &C) const {
    103   // HACK: This entire check is to handle two messages in the Cocoa frameworks:
    104   // -[NSAssertionHandler
    105   //    handleFailureInMethod:object:file:lineNumber:description:]
    106   // -[NSAssertionHandler
    107   //    handleFailureInFunction:file:lineNumber:description:]
    108   // Eventually these should be annotated with __attribute__((noreturn)).
    109   // Because ObjC messages use dynamic dispatch, it is not generally safe to
    110   // assume certain methods can't return. In cases where it is definitely valid,
    111   // see if you can mark the methods noreturn or analyzer_noreturn instead of
    112   // adding more explicit checks to this method.
    113 
    114   if (!Msg.isInstanceMessage())
    115     return;
    116 
    117   const ObjCInterfaceDecl *Receiver = Msg.getReceiverInterface();
    118   if (!Receiver)
    119     return;
    120   if (!Receiver->getIdentifier()->isStr("NSAssertionHandler"))
    121     return;
    122 
    123   Selector Sel = Msg.getSelector();
    124   switch (Sel.getNumArgs()) {
    125   default:
    126     return;
    127   case 4:
    128     if (!isMultiArgSelector(&Sel, "handleFailureInFunction", "file",
    129                             "lineNumber", "description", NULL))
    130       return;
    131     break;
    132   case 5:
    133     if (!isMultiArgSelector(&Sel, "handleFailureInMethod", "object", "file",
    134                             "lineNumber", "description", NULL))
    135       return;
    136     break;
    137   }
    138 
    139   // If we got here, it's one of the messages we care about.
    140   C.generateSink();
    141 }
    142 
    143 
    144 void ento::registerNoReturnFunctionChecker(CheckerManager &mgr) {
    145   mgr.registerChecker<NoReturnFunctionChecker>();
    146 }
    147