C++ Sema类代码示例

 bool shouldProceed(void *S, void *T) {
   using namespace clang;
   Sema *Sem = (Sema *)S;
   DiagnosticsEngine& Diag = Sem->getDiagnostics();
   cling::Transaction* Trans = (cling::Transaction*)T;
   // Here we will cheat a bit and assume that the warning came from the last
   // stmt, which will be in the 90% of the cases.
   CompoundStmt* CS = cast<CompoundStmt>(Trans->getWrapperFD()->getBody());
   // Skip the NullStmts.
   SourceLocation Loc = CS->getLocStart();
   for(CompoundStmt::const_reverse_body_iterator I = CS->body_rbegin(),
         E = CS->body_rend(); I != E; ++I)
     if (!isa<NullStmt>(*I)) {
       Loc = (*I)->getLocStart();
       break;
     }
   Diag.Report(Loc, diag::warn_null_ptr_deref);
   if (isatty(fileno(stdin))) {
     int input = getchar();
     getchar();
     if (input == 'y' || input == 'Y') 
       return false;
   }
   return true;
 }

// Do we know that we will eventually codegen the given function?
static bool IsKnownEmitted(Sema &S, FunctionDecl *FD) {
  // Templates are emitted when they're instantiated.
  if (FD->isDependentContext())
    return false;

  // When compiling for device, host functions are never emitted.  Similarly,
  // when compiling for host, device and global functions are never emitted.
  // (Technically, we do emit a host-side stub for global functions, but this
  // doesn't count for our purposes here.)
  Sema::CUDAFunctionTarget T = S.IdentifyCUDATarget(FD);
  if (S.getLangOpts().CUDAIsDevice && T == Sema::CFT_Host)
    return false;
  if (!S.getLangOpts().CUDAIsDevice &&
      (T == Sema::CFT_Device || T == Sema::CFT_Global))
    return false;

  // Check whether this function is externally visible -- if so, it's
  // known-emitted.
  //
  // We have to check the GVA linkage of the function's *definition* -- if we
  // only have a declaration, we don't know whether or not the function will be
  // emitted, because (say) the definition could include "inline".
  FunctionDecl *Def = FD->getDefinition();

  if (Def &&
      !isDiscardableGVALinkage(S.getASTContext().GetGVALinkageForFunction(Def)))
    return true;

  // Otherwise, the function is known-emitted if it's in our set of
  // known-emitted functions.
  return S.DeviceKnownEmittedFns.count(FD) > 0;
}

/// Build a call to 'operator co_await' if there is a suitable operator for
/// the given expression.
static ExprResult buildOperatorCoawaitCall(Sema &SemaRef, Scope *S,
                                           SourceLocation Loc, Expr *E) {
  UnresolvedSet<16> Functions;
  SemaRef.LookupOverloadedOperatorName(OO_Coawait, S, E->getType(), QualType(),
                                       Functions);
  return SemaRef.CreateOverloadedUnaryOp(Loc, UO_Coawait, Functions, E);
}

    bool VisitCompoundStmt(CompoundStmt* CS) {
      for(CompoundStmt::body_iterator I = CS->body_begin(), E = CS->body_end();
          I != E; ++I) {
        if (!isa<BinaryOperator>(*I))
          continue;

        const BinaryOperator* BinOp = cast<BinaryOperator>(*I);
        if (isAutoCandidate(BinOp)) {
          ASTContext& C = m_Sema->getASTContext();
          VarDecl* VD 
            = cast<VarDecl>(cast<DeclRefExpr>(BinOp->getLHS())->getDecl());
          TypeSourceInfo* ResTSI = 0;
          TypeSourceInfo* TrivialTSI 
            = C.getTrivialTypeSourceInfo(VD->getType());
          Expr* RHS = BinOp->getRHS();
          m_Sema->DeduceAutoType(TrivialTSI, RHS, ResTSI);
          VD->setTypeSourceInfo(ResTSI);
          VD->setType(ResTSI->getType());
          VD->setInit(RHS);
          Sema::DeclGroupPtrTy VDPtrTy = m_Sema->ConvertDeclToDeclGroup(VD);
          // Transform the AST into a "sane" state. Replace the binary operator
          // with decl stmt, because the binop semantically is a decl with init.
          StmtResult DS = m_Sema->ActOnDeclStmt(VDPtrTy, BinOp->getLocStart(), 
                                                BinOp->getLocEnd());
          assert(!DS.isInvalid() && "Invalid DeclStmt.");
          *I = DS.take();
        }
      }
      return true; // returning false will abort the in-depth traversal.
    }

static void HandleMSP430InterruptAttr(Decl *d,
                                      const AttributeList &Attr, Sema &S) {
  if (Attr.getNumArgs() != 1) {
    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments)
      << Attr.getName() << 1;
    return;
  }

  if (!Attr.isArgExpr(0)) {
    S.Diag(Attr.getLoc(), diag::err_attribute_argument_type) << Attr.getName()
      << AANT_ArgumentIntegerConstant;
    return;
  }

  // FIXME: Check for decl - it should be void ()(void).
  Expr *NumParamsExpr = Attr.getArgAsExpr(0);
  llvm::APSInt NumParams(32);
  if (!NumParamsExpr->isIntegerConstantExpr(NumParams, S.Context)) {
    S.Diag(Attr.getLoc(), diag::err_attribute_argument_type)
      << Attr.getName() << AANT_ArgumentIntegerConstant
      << NumParamsExpr->getSourceRange();
    return;
  }

  unsigned Num = NumParams.getLimitedValue(255);
  if ((Num & 1) || Num > 30) {
    S.Diag(Attr.getLoc(), diag::err_attribute_argument_out_of_bounds)
      << "interrupt" << (int)NumParams.getSExtValue()
      << NumParamsExpr->getSourceRange();
    return;
  }

  d->addAttr(::new (S.Context) MSP430InterruptAttr(Attr.getLoc(), S.Context, Num));
  d->addAttr(::new (S.Context) UsedAttr(Attr.getLoc(), S.Context));
}

static bool isValidCoroutineContext(Sema &S, SourceLocation Loc,
                                    StringRef Keyword) {
  // 'co_await' and 'co_yield' are not permitted in unevaluated operands.
  if (S.isUnevaluatedContext()) {
    S.Diag(Loc, diag::err_coroutine_unevaluated_context) << Keyword;
    return false;
  }

  // Any other usage must be within a function.
  auto *FD = dyn_cast<FunctionDecl>(S.CurContext);
  if (!FD) {
    S.Diag(Loc, isa<ObjCMethodDecl>(S.CurContext)
                    ? diag::err_coroutine_objc_method
                    : diag::err_coroutine_outside_function) << Keyword;
    return false;
  }

  // An enumeration for mapping the diagnostic type to the correct diagnostic
  // selection index.
  enum InvalidFuncDiag {
    DiagCtor = 0,
    DiagDtor,
    DiagCopyAssign,
    DiagMoveAssign,
    DiagMain,
    DiagConstexpr,
    DiagAutoRet,
    DiagVarargs,
  };
  bool Diagnosed = false;
  auto DiagInvalid = [&](InvalidFuncDiag ID) {
    S.Diag(Loc, diag::err_coroutine_invalid_func_context) << ID << Keyword;
    Diagnosed = true;
    return false;
  };

  // Diagnose when a constructor, destructor, copy/move assignment operator,
  // or the function 'main' are declared as a coroutine.
  auto *MD = dyn_cast<CXXMethodDecl>(FD);
  if (MD && isa<CXXConstructorDecl>(MD))
    return DiagInvalid(DiagCtor);
  else if (MD && isa<CXXDestructorDecl>(MD))
    return DiagInvalid(DiagDtor);
  else if (MD && MD->isCopyAssignmentOperator())
    return DiagInvalid(DiagCopyAssign);
  else if (MD && MD->isMoveAssignmentOperator())
    return DiagInvalid(DiagMoveAssign);
  else if (FD->isMain())
    return DiagInvalid(DiagMain);

  // Emit a diagnostics for each of the following conditions which is not met.
  if (FD->isConstexpr())
    DiagInvalid(DiagConstexpr);
  if (FD->getReturnType()->isUndeducedType())
    DiagInvalid(DiagAutoRet);
  if (FD->isVariadic())
    DiagInvalid(DiagVarargs);

  return !Diagnosed;
}

static void HandleDLLImportAttr(Decl *D, const AttributeList &Attr, Sema &S) {
  // Attribute can be applied only to functions or variables.
  FunctionDecl *FD = dyn_cast<FunctionDecl>(D);
  if (!FD && !isa<VarDecl>(D)) {
    // Apparently Visual C++ thinks it is okay to not emit a warning
    // in this case, so only emit a warning when -fms-extensions is not
    // specified.
    if (!S.getLangOpts().MicrosoftExt)
      S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type)
        << Attr.getName() << 2 /*variable and function*/;
    return;
  }

  // Currently, the dllimport attribute is ignored for inlined functions.
  // Warning is emitted.
  if (FD && FD->isInlineSpecified()) {
    S.Diag(Attr.getLoc(), diag::warn_attribute_ignored) << Attr.getName();
    return;
  }

  unsigned Index = Attr.getAttributeSpellingListIndex();
  DLLImportAttr *NewAttr = S.mergeDLLImportAttr(D, Attr.getRange(), Index);
  if (NewAttr)
    D->addAttr(NewAttr);
}

static void EraseUnwantedCUDAMatchesImpl(Sema &S, const FunctionDecl *Caller,
                                         llvm::SmallVectorImpl<T> &Matches,
                                         FetchDeclFn FetchDecl) {
  assert(S.getLangOpts().CUDATargetOverloads &&
         "Should not be called w/o enabled target overloads.");
  if (Matches.size() <= 1)
    return;

  // Find the best call preference among the functions in Matches.
  Sema::CUDAFunctionPreference P, BestCFP = Sema::CFP_Never;
  for (auto const &Match : Matches) {
    P = S.IdentifyCUDAPreference(Caller, FetchDecl(Match));
    if (P > BestCFP)
      BestCFP = P;
  }

  // Erase all functions with lower priority.
  for (unsigned I = 0, N = Matches.size(); I != N;)
    if (S.IdentifyCUDAPreference(Caller, FetchDecl(Matches[I])) < BestCFP) {
      Matches[I] = Matches[--N];
      Matches.resize(N);
    } else {
      ++I;
    }
}

static ExprResult buildCoroutineHandle(Sema &S, QualType PromiseType,
                                       SourceLocation Loc) {
  QualType CoroHandleType = lookupCoroutineHandleType(S, PromiseType, Loc);
  if (CoroHandleType.isNull())
    return ExprError();

  DeclContext *LookupCtx = S.computeDeclContext(CoroHandleType);
  LookupResult Found(S, &S.PP.getIdentifierTable().get("from_address"), Loc,
                     Sema::LookupOrdinaryName);
  if (!S.LookupQualifiedName(Found, LookupCtx)) {
    S.Diag(Loc, diag::err_coroutine_handle_missing_member)
        << "from_address";
    return ExprError();
  }

  Expr *FramePtr =
      buildBuiltinCall(S, Loc, Builtin::BI__builtin_coro_frame, {});

  CXXScopeSpec SS;
  ExprResult FromAddr =
      S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
  if (FromAddr.isInvalid())
    return ExprError();

  return S.ActOnCallExpr(nullptr, FromAddr.get(), Loc, FramePtr, Loc);
}

static void HandleX86ForceAlignArgPointerAttr(Decl *D,
                                              const AttributeList& Attr,
                                              Sema &S) {
  // Check the attribute arguments.
  if (Attr.getNumArgs() != 0) {
    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 0;
    return;
  }

  // If we try to apply it to a function pointer, don't warn, but don't
  // do anything, either. It doesn't matter anyway, because there's nothing
  // special about calling a force_align_arg_pointer function.
  ValueDecl *VD = dyn_cast<ValueDecl>(D);
  if (VD && VD->getType()->isFunctionPointerType())
    return;
  // Also don't warn on function pointer typedefs.
  TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(D);
  if (TD && (TD->getUnderlyingType()->isFunctionPointerType() ||
             TD->getUnderlyingType()->isFunctionType()))
    return;
  // Attribute can only be applied to function types.
  if (!isa<FunctionDecl>(D)) {
    S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type)
      << Attr.getName() << /* function */0;
    return;
  }

  D->addAttr(::new (S.Context) X86ForceAlignArgPointerAttr(Attr.getRange(),
                                                           S.Context));
}

static void HandleDLLExportAttr(Decl *D, const AttributeList &Attr, Sema &S) {
  // check the attribute arguments.
  if (Attr.getNumArgs() != 0) {
    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 0;
    return;
  }

  // Attribute can be applied only to functions or variables.
  FunctionDecl *FD = dyn_cast<FunctionDecl>(D);
  if (!FD && !isa<VarDecl>(D)) {
    S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type)
      << Attr.getName() << 2 /*variable and function*/;
    return;
  }

  // Currently, the dllexport attribute is ignored for inlined functions, unless
  // the -fkeep-inline-functions flag has been used. Warning is emitted;
  if (FD && FD->isInlineSpecified()) {
    // FIXME: ... unless the -fkeep-inline-functions flag has been used.
    S.Diag(Attr.getLoc(), diag::warn_attribute_ignored) << "dllexport";
    return;
  }

  unsigned Index = Attr.getAttributeSpellingListIndex();
  DLLExportAttr *NewAttr = S.mergeDLLExportAttr(D, Attr.getRange(), Index);
  if (NewAttr)
    D->addAttr(NewAttr);
}

static bool CheckNakedParmReference(Expr *E, Sema &S) {
  FunctionDecl *Func = dyn_cast<FunctionDecl>(S.CurContext);
  if (!Func)
    return false;
  if (!Func->hasAttr<NakedAttr>())
    return false;

  SmallVector<Expr*, 4> WorkList;
  WorkList.push_back(E);
  while (WorkList.size()) {
    Expr *E = WorkList.pop_back_val();
    if (isa<CXXThisExpr>(E)) {
      S.Diag(E->getLocStart(), diag::err_asm_naked_this_ref);
      S.Diag(Func->getAttr<NakedAttr>()->getLocation(), diag::note_attribute);
      return true;
    }
    if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
      if (isa<ParmVarDecl>(DRE->getDecl())) {
        S.Diag(DRE->getLocStart(), diag::err_asm_naked_parm_ref);
        S.Diag(Func->getAttr<NakedAttr>()->getLocation(), diag::note_attribute);
        return true;
      }
    }
    for (Stmt *Child : E->children()) {
      if (Expr *E = dyn_cast_or_null<Expr>(Child))
        WorkList.push_back(E);
    }
  }
  return false;
}

static void HandleDLLExportAttr(Decl *D, const AttributeList &Attr, Sema &S) {
  // check the attribute arguments.
  if (Attr.getNumArgs() != 0) {
    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 0;
    return;
  }

  // Attribute can be applied only to functions or variables.
  if (isa<VarDecl>(D)) {
    D->addAttr(::new (S.Context) DLLExportAttr(Attr.getLoc(), S.Context));
    return;
  }

  FunctionDecl *FD = dyn_cast<FunctionDecl>(D);
  if (!FD) {
    S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type)
      << Attr.getName() << 2 /*variable and function*/;
    return;
  }

  // Currently, the dllexport attribute is ignored for inlined functions, unless
  // the -fkeep-inline-functions flag has been used. Warning is emitted;
  if (FD->isInlineSpecified()) {
    // FIXME: ... unless the -fkeep-inline-functions flag has been used.
    S.Diag(Attr.getLoc(), diag::warn_attribute_ignored) << "dllexport";
    return;
  }

  D->addAttr(::new (S.Context) DLLExportAttr(Attr.getLoc(), S.Context));
}

/// HandleAddressSpaceTypeAttribute - Process an address_space attribute on the
/// specified type.  The attribute contains 1 argument, the id of the address
/// space for the type.
static void HandleAddressSpaceTypeAttribute(QualType &Type, 
                                            const AttributeList &Attr, Sema &S){
  // If this type is already address space qualified, reject it.
  // Clause 6.7.3 - Type qualifiers: "No type shall be qualified by qualifiers
  // for two or more different address spaces."
  if (Type.getAddressSpace()) {
    S.Diag(Attr.getLoc(), diag::err_attribute_address_multiple_qualifiers);
    return;
  }
  
  // Check the attribute arguments.
  if (Attr.getNumArgs() != 1) {
    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 1;
    return;
  }
  Expr *ASArgExpr = static_cast<Expr *>(Attr.getArg(0));
  llvm::APSInt addrSpace(32);
  if (!ASArgExpr->isIntegerConstantExpr(addrSpace, S.Context)) {
    S.Diag(Attr.getLoc(), diag::err_attribute_address_space_not_int)
      << ASArgExpr->getSourceRange();
    return;
  }

  unsigned ASIdx = static_cast<unsigned>(addrSpace.getZExtValue()); 
  Type = S.Context.getAddrSpaceQualType(Type, ASIdx);
}

/// HandleObjCGCTypeAttribute - Process an objc's gc attribute on the
/// specified type.  The attribute contains 1 argument, weak or strong.
static void HandleObjCGCTypeAttribute(QualType &Type, 
                                      const AttributeList &Attr, Sema &S) {
  if (Type.getObjCGCAttr() != QualType::GCNone) {
    S.Diag(Attr.getLoc(), diag::err_attribute_multiple_objc_gc);
    return;
  }
  
  // Check the attribute arguments.
  if (!Attr.getParameterName()) {    
    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_string)
      << "objc_gc" << 1;
    return;
  }
  QualType::GCAttrTypes GCAttr;
  if (Attr.getNumArgs() != 0) {
    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 1;
    return;
  }
  if (Attr.getParameterName()->isStr("weak")) 
    GCAttr = QualType::Weak;
  else if (Attr.getParameterName()->isStr("strong"))
    GCAttr = QualType::Strong;
  else {
    S.Diag(Attr.getLoc(), diag::warn_attribute_type_not_supported)
      << "objc_gc" << Attr.getParameterName();
    return;
  }
  
  Type = S.Context.getObjCGCQualType(Type, GCAttr);
}