C# CodeGen.BeginExceptionBlock方法代码示例

        // ***WITH STATEMENT CODE GENERATION ALGORITHM***
        //
        //GRAMMAR :=
        //with EXPR as VAR:
        //    BLOCK
        //
        //CODE GEN :=
        //
        //mgr = (EXPR)
        //exit = mgr.__exit__  # Not calling it yet
        //value = mgr.__enter__()
        //exc = True
        //isTryYielded = False
        //try:
        //
        //   VAR = value  # Only if "as VAR" is present
        //   BLOCK
        //   // if yield happens in the Block,
        //   // then isTryYielded is set to True by Yield's Code Gen
        //except:
        //   # The exceptional case is handled here
        //   exc = False
        //   if not exit(*sys.exc_info()):
        //        raise
        //   # The exception is consumed if exit() returns true
        //finally:
        //    # The normal and non-local-goto cases are handled here
        //    if  isTryYielded = False && exc == True :
        //        exit(None, None, None)
        internal override void Emit(CodeGen cg)
        {
            Slot exc = null;
            Slot isTryYielded = null;
            Slot exit = null;

            if (cg.IsGenerator()) {
                exc = cg.Names.GetTempSlot("with", typeof(object));
                isTryYielded = cg.Names.GetTempSlot("with", typeof(object));
                exit = cg.Names.GetTempSlot("with", typeof(object));
            } else {
                exc = cg.GetLocalTmp(typeof(object));
                isTryYielded = cg.GetLocalTmp(typeof(object));
                exit = cg.GetLocalTmp(typeof(object));
            }

            // mgr = (EXPR)
            Slot mgr = cg.GetLocalTmp(typeof(object));
            contextManager.Emit(cg);
            mgr.EmitSet(cg);

            // exit = mgr.__exit__ # not calling it yet
            cg.EmitCallerContext();
            mgr.EmitGet(cg);
            cg.EmitSymbolId("__exit__");
            cg.EmitCall(typeof(Ops), "GetAttr");
            exit.EmitSet(cg);

            mgr.EmitGet(cg);
            cg.FreeLocalTmp(mgr);
            cg.EmitSymbolId("__enter__");
            cg.EmitObjectArray(new Expression[0]);
            cg.EmitCall(typeof(Ops), "Invoke", new Type[] { typeof(object), typeof(SymbolId), typeof(object[]) });
            Slot value = cg.GetLocalTmp(typeof(object));
            value.EmitSet(cg);

            // exc = True
            cg.EmitConstantBoxed(true);
            exc.EmitSet(cg);

            Slot choiceVar = null;

            if (yieldTargets != null && yieldTargets.Count > 0) {
                Label startOfBlock = cg.DefineLabel();
                choiceVar = cg.GetLocalTmp(typeof(int));
                cg.EmitInt(-1);
                choiceVar.EmitSet(cg);
                cg.Emit(OpCodes.Br, startOfBlock);

                int index = 0;
                foreach (YieldTarget yt in yieldTargets) {
                    cg.MarkLabel(yt.TopBranchTarget);
                    cg.EmitInt(index++);
                    choiceVar.EmitSet(cg);
                    cg.Emit(OpCodes.Br, startOfBlock);
                }

                cg.MarkLabel(startOfBlock);
            }

            cg.EmitConstantBoxed(false);
            isTryYielded.EmitSet(cg);

            Label beforeFinally = cg.DefineLabel();

            cg.PushWithTryBlock(isTryYielded);
            cg.BeginExceptionBlock();

            if (yieldTargets != null && yieldTargets.Count > 0) {
                int index = 0;
                foreach (YieldTarget yt in yieldTargets) {
//.........这里部分代码省略.........

        private void EmitSimpleTry(CodeGen cg, TryFlowResult flow)
        {
            //
            // Initialize the flow control flag
            //
            Slot flowControlFlag = null;
            if (flow.Any) {
                Debug.Assert(_finally != null);

                flowControlFlag = cg.GetLocalTmp(typeof(int));
                cg.EmitInt(CodeGen.FinallyExitsNormally);
                flowControlFlag.EmitSet(cg);

                //  If there is a control flow in finally, emit outer:
                //  try {
                //      // try block body and all catch handling
                //  } catch (Exception all) {
                //      saved = all;
                //  } finally {
                //      finally_body
                //      if (saved != null) {
                //          throw saved;
                //      }
                //  }

                if (HaveHandlers()) {
                    cg.PushExceptionBlock(TargetBlockType.Try, flowControlFlag);
                    cg.BeginExceptionBlock();
                }
            }

            //******************************************************************
            // 1. ENTERING TRY
            //******************************************************************

            cg.PushExceptionBlock(TargetBlockType.Try, flowControlFlag);
            cg.BeginExceptionBlock();

            //******************************************************************
            // 2. Emit the try statement body
            //******************************************************************

            _body.Emit(cg);
            //cg.EmitSequencePointNone();

            //******************************************************************
            // 3. Emit the catch blocks
            //******************************************************************

            if (HaveHandlers()) {
                cg.PushExceptionBlock(TargetBlockType.Catch, flowControlFlag);

                foreach (CatchBlock cb in _handlers) {
                    // Begin the strongly typed exception block
                    cg.BeginCatchBlock(cb.Test);

                    // Save the exception (if the catch block asked for it) or pop
                    EmitSaveExceptionOrPop(cg, cb);

                    //
                    // Emit the catch block body
                    //
                    cb.Body.Emit(cg);
                }

                cg.PopTargets(TargetBlockType.Catch);
            }

            //******************************************************************
            // 4. Emit the finally block
            //******************************************************************

            if (_finally != null) {
                Slot rethrow = null;
                if (flow.Any) {
                    // If there is a control flow in finally, end the catch
                    // statement and emit the catch-all and finally clause
                    // with rethrow at the end.

                    if (HaveHandlers()) {
                        cg.EndExceptionBlock();
                        cg.PopTargets(TargetBlockType.Try);
                    }

                    cg.PushExceptionBlock(TargetBlockType.Catch, flowControlFlag);
                    cg.BeginCatchBlock(typeof(Exception));

                    rethrow = cg.GetLocalTmp(typeof(Exception));
                    rethrow.EmitSet(cg);

                    cg.PopTargets(TargetBlockType.Catch);
                }

                cg.PushExceptionBlock(TargetBlockType.Finally, flowControlFlag);
                cg.BeginFinallyBlock();

                //
                // Emit the finally block body
                //
                _finally.Emit(cg);
//.........这里部分代码省略.........

        private void EmitGenerator(CodeGen ncg)
        {
            YieldTarget[] targets = YieldLabelBuilder.BuildYieldTargets(this, ncg);

            Label[] jumpTable = new Label[yieldCount];
            for (int i = 0; i < yieldCount; i++) jumpTable[i] = targets[i].TopBranchTarget;
            ncg.yieldLabels = jumpTable;

            // Generator will ofcourse yield, but we are not interested in the isBlockYielded value
            // hence push a dummySlot to pass the Assertion.

            Slot dummySlot = ncg.GetLocalTmp(typeof(object));
            ncg.PushTryBlock(dummySlot);
            ncg.BeginExceptionBlock();

            ncg.Emit(OpCodes.Ldarg_0);
            ncg.EmitFieldGet(typeof(Generator), "location");
            ncg.Emit(OpCodes.Switch, jumpTable);

            // fall-through on first pass
            // yield statements will insert the needed labels after their returns
            Body.Emit(ncg);
            //free the dummySlot
            ncg.FreeLocalTmp(dummySlot);
            // fall-through is almost always possible in generators, so this
            // is almost always needed
            ncg.EmitReturnInGenerator(null);

            // special handling for StopIteration thrown in body
            ncg.BeginCatchBlock(typeof(StopIterationException));
            ncg.EndExceptionBlock();
            ncg.EmitReturnInGenerator(null);
            ncg.PopTargets();

            ncg.Finish();
        }

        private void EmitGeneratorTry(CodeGen cg, TryFlowResult flow)
        {
            //
            // Initialize the flow control flag
            //
            Slot flowControlFlag = null;

            if (flow.Any) {
                flowControlFlag = cg.GetLocalTmp(typeof(int));
                cg.EmitInt(CodeGen.FinallyExitsNormally);
                flowControlFlag.EmitSet(cg);
            }

            Slot exception = null;
            if (_finally != null) {
                exception = cg.GetTemporarySlot(typeof(Exception));
                cg.EmitNull();
                exception.EmitSet(cg);
            }

            //******************************************************************
            // Entering the try block
            //******************************************************************

            if (_target != null) {
                cg.MarkLabel(_target.EnsureLabel(cg));
            }

            //******************************************************************
            // If we have a 'finally', transform it into try..catch..finally
            // and rethrow
            //******************************************************************
            Label endFinallyBlock = new Label();
            if (_finally != null) {
                cg.PushExceptionBlock(TargetBlockType.Try, flowControlFlag);
                cg.BeginExceptionBlock();
                endFinallyBlock = cg.DefineLabel();

                //**************************************************************
                // If there is a yield in any catch, that catch will be hoisted
                // and we need to dispatch to it from here
                //**************************************************************
                if (_yieldInCatch) {
                    EmitYieldDispatch(_catchYields, cg);
                }

                if (YieldInBlock(_finallyYields)) {
                    foreach (YieldTarget yt in _finallyYields) {
                        cg.GotoRouter.EmitGet(cg);
                        cg.EmitInt(yt.Index);
                        cg.Emit(OpCodes.Beq, endFinallyBlock);
                    }
                }
            }

            //******************************************************************
            // If we have a 'catch', start a try block to handle all the catches
            //******************************************************************

            Label endCatchBlock = new Label();
            if (HaveHandlers()) {
                cg.PushExceptionBlock(TargetBlockType.Try, flowControlFlag);
                endCatchBlock = cg.BeginExceptionBlock();
            }

            //******************************************************************
            // Emit the try block body
            //******************************************************************

            // First, emit the dispatch within the try block
            EmitYieldDispatch(_tryYields, cg);

            // Then, emit the actual body
            _body.Emit(cg);
            //cg.EmitSequencePointNone();

            //******************************************************************
            // Emit the catch blocks
            //******************************************************************

            if (HaveHandlers()) {
                List<CatchRecord> catches = new List<CatchRecord>();
                cg.PushExceptionBlock(TargetBlockType.Catch, flowControlFlag);

                foreach (CatchBlock cb in _handlers) {
                    cg.BeginCatchBlock(cb.Test);

                    if (cb.Yield) {
                        // The catch block body contains yield, therefore
                        // delay the body emit till after the try block.
                        Slot slot = cg.GetLocalTmp(cb.Test);
                        slot.EmitSet(cg);
                        catches.Add(new CatchRecord(slot, cb));
                    } else {
                        // Save the exception (if the catch block asked for it) or pop
                        EmitSaveExceptionOrPop(cg, cb);
                        // Emit the body right now, since it doesn't contain yield
                        cb.Body.Emit(cg);
                    }
                }
//.........这里部分代码省略.........