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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/AST/Attr.h"
     17 #include "clang/StaticAnalyzer/Core/Checker.h"
     18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
     19 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
     20 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
     21 #include "llvm/ADT/StringSwitch.h"
     22 #include <cstdarg>
     23 
     24 using namespace clang;
     25 using namespace ento;
     26 
     27 namespace {
     28 
     29 class NoReturnFunctionChecker : public Checker< check::PostCall,
     30                                                 check::PostObjCMessage > {
     31 public:
     32   void checkPostCall(const CallEvent &CE, CheckerContext &C) const;
     33   void checkPostObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
     34 };
     35 
     36 }
     37 
     38 void NoReturnFunctionChecker::checkPostCall(const CallEvent &CE,
     39                                             CheckerContext &C) const {
     40   ProgramStateRef state = C.getState();
     41   bool BuildSinks = false;
     42 
     43   if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(CE.getDecl()))
     44     BuildSinks = FD->getAttr<AnalyzerNoReturnAttr>() || FD->isNoReturn();
     45 
     46   const Expr *Callee = CE.getOriginExpr();
     47   if (!BuildSinks && Callee)
     48     BuildSinks = getFunctionExtInfo(Callee->getType()).getNoReturn();
     49 
     50   if (!BuildSinks && CE.isGlobalCFunction()) {
     51     if (const IdentifierInfo *II = CE.getCalleeIdentifier()) {
     52       // HACK: Some functions are not marked noreturn, and don't return.
     53       //  Here are a few hardwired ones.  If this takes too long, we can
     54       //  potentially cache these results.
     55       BuildSinks
     56         = llvm::StringSwitch<bool>(StringRef(II->getName()))
     57             .Case("exit", true)
     58             .Case("panic", true)
     59             .Case("error", true)
     60             .Case("Assert", true)
     61             // FIXME: This is just a wrapper around throwing an exception.
     62             //  Eventually inter-procedural analysis should handle this easily.
     63             .Case("ziperr", true)
     64             .Case("assfail", true)
     65             .Case("db_error", true)
     66             .Case("__assert", true)
     67             .Case("__assert_rtn", true)
     68             .Case("__assert_fail", true)
     69             .Case("dtrace_assfail", true)
     70             .Case("yy_fatal_error", true)
     71             .Case("_XCAssertionFailureHandler", true)
     72             .Case("_DTAssertionFailureHandler", true)
     73             .Case("_TSAssertionFailureHandler", true)
     74             .Default(false);
     75     }
     76   }
     77 
     78   if (BuildSinks)
     79     C.generateSink();
     80 }
     81 
     82 static bool END_WITH_NULL isMultiArgSelector(const Selector *Sel, ...) {
     83   va_list argp;
     84   va_start(argp, Sel);
     85 
     86   unsigned Slot = 0;
     87   const char *Arg;
     88   while ((Arg = va_arg(argp, const char *))) {
     89     if (!Sel->getNameForSlot(Slot).equals(Arg))
     90       break; // still need to va_end!
     91     ++Slot;
     92   }
     93 
     94   va_end(argp);
     95 
     96   // We only succeeded if we made it to the end of the argument list.
     97   return (Arg == NULL);
     98 }
     99 
    100 void NoReturnFunctionChecker::checkPostObjCMessage(const ObjCMethodCall &Msg,
    101                                                    CheckerContext &C) const {
    102   // Check if the method is annotated with analyzer_noreturn.
    103   if (const ObjCMethodDecl *MD = Msg.getDecl()) {
    104     MD = MD->getCanonicalDecl();
    105     if (MD->hasAttr<AnalyzerNoReturnAttr>()) {
    106       C.generateSink();
    107       return;
    108     }
    109   }
    110 
    111   // HACK: This entire check is to handle two messages in the Cocoa frameworks:
    112   // -[NSAssertionHandler
    113   //    handleFailureInMethod:object:file:lineNumber:description:]
    114   // -[NSAssertionHandler
    115   //    handleFailureInFunction:file:lineNumber:description:]
    116   // Eventually these should be annotated with __attribute__((noreturn)).
    117   // Because ObjC messages use dynamic dispatch, it is not generally safe to
    118   // assume certain methods can't return. In cases where it is definitely valid,
    119   // see if you can mark the methods noreturn or analyzer_noreturn instead of
    120   // adding more explicit checks to this method.
    121 
    122   if (!Msg.isInstanceMessage())
    123     return;
    124 
    125   const ObjCInterfaceDecl *Receiver = Msg.getReceiverInterface();
    126   if (!Receiver)
    127     return;
    128   if (!Receiver->getIdentifier()->isStr("NSAssertionHandler"))
    129     return;
    130 
    131   Selector Sel = Msg.getSelector();
    132   switch (Sel.getNumArgs()) {
    133   default:
    134     return;
    135   case 4:
    136     if (!isMultiArgSelector(&Sel, "handleFailureInFunction", "file",
    137                             "lineNumber", "description", NULL))
    138       return;
    139     break;
    140   case 5:
    141     if (!isMultiArgSelector(&Sel, "handleFailureInMethod", "object", "file",
    142                             "lineNumber", "description", NULL))
    143       return;
    144     break;
    145   }
    146 
    147   // If we got here, it's one of the messages we care about.
    148   C.generateSink();
    149 }
    150 
    151 
    152 void ento::registerNoReturnFunctionChecker(CheckerManager &mgr) {
    153   mgr.registerChecker<NoReturnFunctionChecker>();
    154 }
    155