In ilasm/codegen:

[mcs.git] / mcs / codegen.cs

//
// codegen.cs: The code generator
//
// Author:
//   Miguel de Icaza (miguel@ximian.com)
//
// (C) 2001, 2002, 2003 Ximian, Inc.
// (C) 2004 Novell, Inc.
//

#if !DEBUG
        #define PRODUCTION
#endif

using System;
using System.IO;
using System.Collections;
using System.Collections.Specialized;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Cryptography;
using System.Security.Permissions;

using Mono.Security.Cryptography;

namespace Mono.CSharp {

        /// <summary>
        ///    Code generator class.
        /// </summary>
        public class CodeGen {
                static AppDomain current_domain;
                static public SymbolWriter SymbolWriter;

                public static AssemblyClass Assembly;
                public static ModuleClass Module;

                static CodeGen ()
                {
                        Reset ();
                }

                public static void Reset ()
                {
                        Assembly = new AssemblyClass ();
                        Module = new ModuleClass (RootContext.Unsafe);
                }

                public static string Basename (string name)
                {
                        int pos = name.LastIndexOf ('/');

                        if (pos != -1)
                                return name.Substring (pos + 1);

                        pos = name.LastIndexOf ('\\');
                        if (pos != -1)
                                return name.Substring (pos + 1);

                        return name;
                }

                public static string Dirname (string name)
                {
                        int pos = name.LastIndexOf ('/');

                        if (pos != -1)
                                return name.Substring (0, pos);

                        pos = name.LastIndexOf ('\\');
                        if (pos != -1)
                                return name.Substring (0, pos);

                        return ".";
                }

                static public string FileName;

                //
                // Initializes the symbol writer
                //
                static void InitializeSymbolWriter (string filename)
                {
                        SymbolWriter = SymbolWriter.GetSymbolWriter (Module.Builder, filename);

                        //
                        // If we got an ISymbolWriter instance, initialize it.
                        //
                        if (SymbolWriter == null) {
                                Report.Warning (
                                        -18, 1, "Could not find the symbol writer assembly (Mono.CompilerServices.SymbolWriter.dll). This is normally an installation problem. Please make sure to compile and install the mcs/class/Mono.CompilerServices.SymbolWriter directory.");
                                return;
                        }
                }

                //
                // Initializes the code generator variables
                //
                static public bool Init (string name, string output, bool want_debugging_support)
                {
                        FileName = output;
                        AssemblyName an = Assembly.GetAssemblyName (name, output);
                        if (an == null)
                                return false;

                        if (an.KeyPair != null) {
                                // If we are going to strong name our assembly make
                                // sure all its refs are strong named
                                foreach (Assembly a in RootNamespace.Global.Assemblies) {
                                        AssemblyName ref_name = a.GetName ();
                                        byte [] b = ref_name.GetPublicKeyToken ();
                                        if (b == null || b.Length == 0) {
                                                Report.Error (1577, "Assembly generation failed " +
                                                                "-- Referenced assembly '" +
                                                                ref_name.Name +
                                                                "' does not have a strong name.");
                                                //Environment.Exit (1);
                                        }
                                }
                        }
                        
                        current_domain = AppDomain.CurrentDomain;

                        try {
                                Assembly.Builder = current_domain.DefineDynamicAssembly (an,
                                        AssemblyBuilderAccess.Save, Dirname (name));
                        }
                        catch (ArgumentException) {
                                // specified key may not be exportable outside it's container
                                if (RootContext.StrongNameKeyContainer != null) {
                                        Report.Error (1548, "Could not access the key inside the container `" +
                                                RootContext.StrongNameKeyContainer + "'.");
                                        Environment.Exit (1);
                                }
                                return false;
                        }
                        catch (CryptographicException) {
                                if ((RootContext.StrongNameKeyContainer != null) || (RootContext.StrongNameKeyFile != null)) {
                                        Report.Error (1548, "Could not use the specified key to strongname the assembly.");
                                        Environment.Exit (1);
                                }
                                return false;
                        }

                        //
                        // Pass a path-less name to DefineDynamicModule.  Wonder how
                        // this copes with output in different directories then.
                        // FIXME: figure out how this copes with --output /tmp/blah
                        //
                        // If the third argument is true, the ModuleBuilder will dynamically
                        // load the default symbol writer.
                        //
                        Module.Builder = Assembly.Builder.DefineDynamicModule (
                                Basename (name), Basename (output), false);

                        if (want_debugging_support)
                                InitializeSymbolWriter (output);

                        return true;
                }

                static public void Save (string name)
                {
                        try {
                                Assembly.Builder.Save (Basename (name));
                        }
                        catch (COMException) {
                                if ((RootContext.StrongNameKeyFile == null) || (!RootContext.StrongNameDelaySign))
                                        throw;

                                // FIXME: it seems Microsoft AssemblyBuilder doesn't like to delay sign assemblies 
                                Report.Error (1548, "Couldn't delay-sign the assembly with the '" +
                                        RootContext.StrongNameKeyFile +
                                        "', Use MCS with the Mono runtime or CSC to compile this assembly.");
                        }
                        catch (System.IO.IOException io) {
                                Report.Error (16, "Could not write to file `"+name+"', cause: " + io.Message);
                        }
                        catch (System.UnauthorizedAccessException ua) {
                                Report.Error (16, "Could not write to file `"+name+"', cause: " + ua.Message);
                        }

                        if (SymbolWriter != null)
                                SymbolWriter.WriteSymbolFile ();
                }
        }

        /// <summary>
        ///   An Emit Context is created for each body of code (from methods,
        ///   properties bodies, indexer bodies or constructor bodies)
        /// </summary>
        public class EmitContext {
                public DeclSpace DeclSpace;
                public DeclSpace TypeContainer;
                public ILGenerator   ig;

                /// <summary>
                ///   This variable tracks the `checked' state of the compilation,
                ///   it controls whether we should generate code that does overflow
                ///   checking, or if we generate code that ignores overflows.
                ///
                ///   The default setting comes from the command line option to generate
                ///   checked or unchecked code plus any source code changes using the
                ///   checked/unchecked statements or expressions.   Contrast this with
                ///   the ConstantCheckState flag.
                /// </summary>
                
                public bool CheckState;

                /// <summary>
                ///   The constant check state is always set to `true' and cant be changed
                ///   from the command line.  The source code can change this setting with
                ///   the `checked' and `unchecked' statements and expressions. 
                /// </summary>
                public bool ConstantCheckState;

                /// <summary>
                ///   Whether we are emitting code inside a static or instance method
                /// </summary>
                public bool IsStatic;

                /// <summary>
                ///   Whether the actual created method is static or instance method.
                ///   Althoug the method might be declared as `static', if an anonymous
                ///   method is involved, we might turn this into an instance method.
                ///
                ///   So this reflects the low-level staticness of the method, while
                ///   IsStatic represents the semantic, high-level staticness.
                /// </summary>
                public bool MethodIsStatic;

                /// <summary>
                ///   Whether we are emitting a field initializer
                /// </summary>
                public bool IsFieldInitializer;

                /// <summary>
                ///   The value that is allowed to be returned or NULL if there is no
                ///   return type.
                /// </summary>
                public Type ReturnType;

                /// <summary>
                ///   Points to the Type (extracted from the TypeContainer) that
                ///   declares this body of code
                /// </summary>
                public Type ContainerType;
                
                /// <summary>
                ///   Whether this is generating code for a constructor
                /// </summary>
                public bool IsConstructor;

                /// <summary>
                ///   Whether we're control flow analysis enabled
                /// </summary>
                public bool DoFlowAnalysis;

                /// <summary>
                ///   Whether we're control flow analysis disabled on struct
                /// </summary>
                public bool OmitStructFlowAnalysis;

                /// <summary>
                ///   Keeps track of the Type to LocalBuilder temporary storage created
                ///   to store structures (used to compute the address of the structure
                ///   value on structure method invocations)
                /// </summary>
                public Hashtable temporary_storage;

                public Block CurrentBlock;

                public int CurrentFile;

                /// <summary>
                ///   The location where we store the return value.
                /// </summary>
                LocalBuilder return_value;

                /// <summary>
                ///   The location where return has to jump to return the
                ///   value
                /// </summary>
                public Label ReturnLabel;

                /// <summary>
                ///   If we already defined the ReturnLabel
                /// </summary>
                public bool HasReturnLabel;

                /// <summary>
                ///   Whether we are inside an iterator block.
                /// </summary>
                public bool InIterator;

                public bool IsLastStatement;

                /// <summary>
                ///  Whether we are inside an unsafe block
                /// </summary>
                public bool InUnsafe;

                /// <summary>
                ///  Whether we are in a `fixed' initialization
                /// </summary>
                public bool InFixedInitializer;

                public bool InRefOutArgumentResolving;

                public bool InCatch;
                public bool InFinally;

                /// <summary>
                ///  Whether we are inside an anonymous method.
                /// </summary>
                public AnonymousContainer CurrentAnonymousMethod;
                
                /// <summary>
                ///   Location for this EmitContext
                /// </summary>
                public Location loc;

                /// <summary>
                ///   Inside an enum definition, we do not resolve enumeration values
                ///   to their enumerations, but rather to the underlying type/value
                ///   This is so EnumVal + EnumValB can be evaluated.
                ///
                ///   There is no "E operator + (E x, E y)", so during an enum evaluation
                ///   we relax the rules
                /// </summary>
                public bool InEnumContext;

                /// <summary>
                ///   Anonymous methods can capture local variables and fields,
                ///   this object tracks it.  It is copied from the TopLevelBlock
                ///   field.
                /// </summary>
                public CaptureContext capture_context;

                /// <summary>
                /// Trace when method is called and is obsolete then this member suppress message
                /// when call is inside next [Obsolete] method or type.
                /// </summary>
                public bool TestObsoleteMethodUsage = true;

                /// <summary>
                ///    The current iterator
                /// </summary>
                public Iterator CurrentIterator;

                /// <summary>
                ///    Whether we are in the resolving stage or not
                /// </summary>
                enum Phase {
                        Created,
                        Resolving,
                        Emitting
                }
                
                Phase current_phase;
                FlowBranching current_flow_branching;

                static int next_id = 0;
                int id = ++next_id;

                public override string ToString ()
                {
                        return String.Format ("EmitContext ({0}:{1}:{2})", id,
                                              CurrentIterator, capture_context, loc);
                }
                
                public EmitContext (DeclSpace parent, DeclSpace ds, Location l, ILGenerator ig,
                                    Type return_type, int code_flags, bool is_constructor)
                {
                        this.ig = ig;

                        TypeContainer = parent;
                        DeclSpace = ds;
                        CheckState = RootContext.Checked;
                        ConstantCheckState = true;

                        IsStatic = (code_flags & Modifiers.STATIC) != 0;
                        MethodIsStatic = IsStatic;
                        InIterator = (code_flags & Modifiers.METHOD_YIELDS) != 0;
                        ReturnType = return_type;
                        IsConstructor = is_constructor;
                        CurrentBlock = null;
                        CurrentFile = 0;
                        current_phase = Phase.Created;
                        
                        if (parent != null){
                                // Can only be null for the ResolveType contexts.
                                ContainerType = parent.TypeBuilder;
                                if (parent.UnsafeContext)
                                        InUnsafe = true;
                                else
                                        InUnsafe = (code_flags & Modifiers.UNSAFE) != 0;
                        }
                        loc = l;

                        if (ReturnType == TypeManager.void_type)
                                ReturnType = null;
                }

                public EmitContext (TypeContainer tc, Location l, ILGenerator ig,
                                    Type return_type, int code_flags, bool is_constructor)
                        : this (tc, tc, l, ig, return_type, code_flags, is_constructor)
                {
                }

                public EmitContext (TypeContainer tc, Location l, ILGenerator ig,
                                    Type return_type, int code_flags)
                        : this (tc, tc, l, ig, return_type, code_flags, false)
                {
                }

                public FlowBranching CurrentBranching {
                        get {
                                return current_flow_branching;
                        }
                }

                public bool HaveCaptureInfo {
                        get {
                                return capture_context != null;
                        }
                }

                // <summary>
                //   Starts a new code branching.  This inherits the state of all local
                //   variables and parameters from the current branching.
                // </summary>
                public FlowBranching StartFlowBranching (FlowBranching.BranchingType type, Location loc)
                {
                        current_flow_branching = FlowBranching.CreateBranching (CurrentBranching, type, null, loc);
                        return current_flow_branching;
                }

                // <summary>
                //   Starts a new code branching for block `block'.
                // </summary>
                public FlowBranching StartFlowBranching (Block block)
                {
                        FlowBranching.BranchingType type;

                        if ((CurrentBranching != null) &&
                            (CurrentBranching.Type == FlowBranching.BranchingType.Switch))
                                type = FlowBranching.BranchingType.SwitchSection;
                        else
                                type = FlowBranching.BranchingType.Block;

                        DoFlowAnalysis = true;

                        current_flow_branching = FlowBranching.CreateBranching (
                                CurrentBranching, type, block, block.StartLocation);
                        return current_flow_branching;
                }

                public FlowBranchingException StartFlowBranching (ExceptionStatement stmt)
                {
                        FlowBranchingException branching = new FlowBranchingException (
                                CurrentBranching, stmt);
                        current_flow_branching = branching;
                        return branching;
                }

                // <summary>
                //   Ends a code branching.  Merges the state of locals and parameters
                //   from all the children of the ending branching.
                // </summary>
                public FlowBranching.UsageVector DoEndFlowBranching ()
                {
                        FlowBranching old = current_flow_branching;
                        current_flow_branching = current_flow_branching.Parent;

                        return current_flow_branching.MergeChild (old);
                }

                // <summary>
                //   Ends a code branching.  Merges the state of locals and parameters
                //   from all the children of the ending branching.
                // </summary>
                public FlowBranching.Reachability EndFlowBranching ()
                {
                        FlowBranching.UsageVector vector = DoEndFlowBranching ();

                        return vector.Reachability;
                }

                // <summary>
                //   Kills the current code branching.  This throws away any changed state
                //   information and should only be used in case of an error.
                // </summary>
                public void KillFlowBranching ()
                {
                        current_flow_branching = current_flow_branching.Parent;
                }

                public void CaptureVariable (LocalInfo li)
                {
                        capture_context.AddLocal (CurrentAnonymousMethod, li);
                        li.IsCaptured = true;
                }

                public void CaptureParameter (string name, Type t, int idx)
                {
                        capture_context.AddParameter (this, CurrentAnonymousMethod, name, t, idx);
                }

                public void CaptureThis ()
                {
                        capture_context.CaptureThis (CurrentAnonymousMethod);
                }
                
                
                //
                // Use to register a field as captured
                //
                public void CaptureField (FieldExpr fe)
                {
                        capture_context.AddField (this, CurrentAnonymousMethod, fe);
                }

                //
                // Whether anonymous methods have captured variables
                //
                public bool HaveCapturedVariables ()
                {
                        if (capture_context != null)
                                return capture_context.HaveCapturedVariables;
                        return false;
                }

                //
                // Whether anonymous methods have captured fields or this.
                //
                public bool HaveCapturedFields ()
                {
                        if (capture_context != null)
                                return capture_context.HaveCapturedFields;
                        return false;
                }

                //
                // Emits the instance pointer for the host method
                //
                public void EmitMethodHostInstance (EmitContext target, AnonymousMethod am)
                {
                        if (capture_context != null)
                                capture_context.EmitMethodHostInstance (target, am);
                        else if (IsStatic)
                                target.ig.Emit (OpCodes.Ldnull);
                        else
                                target.ig.Emit (OpCodes.Ldarg_0);
                }

                //
                // Returns whether the `local' variable has been captured by an anonymous
                // method
                //
                public bool IsCaptured (LocalInfo local)
                {
                        return capture_context.IsCaptured (local);
                }

                public bool IsParameterCaptured (string name)
                {
                        if (capture_context != null)
                                return capture_context.IsParameterCaptured (name);
                        return false;
                }
                
                public void EmitMeta (ToplevelBlock b)
                {
                        if (capture_context != null)
                                capture_context.EmitAnonymousHelperClasses (this);
                        b.EmitMeta (this);

                        if (HasReturnLabel)
                                ReturnLabel = ig.DefineLabel ();
                }

                //
                // Here until we can fix the problem with Mono.CSharp.Switch, which
                // currently can not cope with ig == null during resolve (which must
                // be fixed for switch statements to work on anonymous methods).
                //
                public void EmitTopBlock (IMethodData md, ToplevelBlock block)
                {
                        if (block == null)
                                return;
                        
                        bool unreachable;
                        
                        if (ResolveTopBlock (null, block, md.ParameterInfo, md, out unreachable)){
                                EmitMeta (block);

                                current_phase = Phase.Emitting;
                                EmitResolvedTopBlock (block, unreachable);
                        }
                }

                bool resolved;

                public bool ResolveTopBlock (EmitContext anonymous_method_host, ToplevelBlock block,
                                             Parameters ip, IMethodData md, out bool unreachable)
                {
                        current_phase = Phase.Resolving;
                        
                        unreachable = false;

                        if (resolved)
                                return true;

                        capture_context = block.CaptureContext;
                        
                        if (!loc.IsNull)
                                CurrentFile = loc.File;

#if PRODUCTION
                        try {
#endif
                                if (!block.ResolveMeta (this, ip))
                                        return false;

                                bool old_do_flow_analysis = DoFlowAnalysis;
                                DoFlowAnalysis = true;

                                if (anonymous_method_host != null)
                                        current_flow_branching = FlowBranching.CreateBranching (
                                                anonymous_method_host.CurrentBranching,
                                                FlowBranching.BranchingType.Block, block, loc);
                                else 
                                        current_flow_branching = block.TopLevelBranching;

                                if (!block.Resolve (this)) {
                                        current_flow_branching = null;
                                        DoFlowAnalysis = old_do_flow_analysis;
                                        return false;
                                }

                                FlowBranching.Reachability reachability = current_flow_branching.MergeTopBlock ();
                                current_flow_branching = null;

                                DoFlowAnalysis = old_do_flow_analysis;

                                if (reachability.AlwaysReturns ||
                                    reachability.AlwaysThrows ||
                                    reachability.IsUnreachable)
                                        unreachable = true;
#if PRODUCTION
                        } catch (Exception e) {
                                        Console.WriteLine ("Exception caught by the compiler while compiling:");
                                        Console.WriteLine ("   Block that caused the problem begin at: " + loc);
                                        
                                        if (CurrentBlock != null){
                                                Console.WriteLine ("                     Block being compiled: [{0},{1}]",
                                                                   CurrentBlock.StartLocation, CurrentBlock.EndLocation);
                                        }
                                        Console.WriteLine (e.GetType ().FullName + ": " + e.Message);
                                        throw;
                        }
#endif

                        if (ReturnType != null && !unreachable) {
                                if (CurrentAnonymousMethod == null) {
                                        Report.Error (161, md.Location, "`{0}': not all code paths return a value", md.GetSignatureForError ());
                                        return false;
                                } else if (!CurrentAnonymousMethod.IsIterator) {
                                        Report.Error (1643, CurrentAnonymousMethod.Location, "Not all code paths return a value in anonymous method of type `{0}'",
                                                CurrentAnonymousMethod.GetSignatureForError ());
                                        return false;
                                }
                        }

                        block.CompleteContexts ();
                        resolved = true;
                        return true;
                }

                public void EmitResolvedTopBlock (ToplevelBlock block, bool unreachable)
                {
                        if (block != null)
                                block.Emit (this);
                        
                        if (HasReturnLabel)
                                ig.MarkLabel (ReturnLabel);
                        
                        if (return_value != null){
                                ig.Emit (OpCodes.Ldloc, return_value);
                                ig.Emit (OpCodes.Ret);
                        } else {
                                //
                                // If `HasReturnLabel' is set, then we already emitted a
                                // jump to the end of the method, so we must emit a `ret'
                                // there.
                                //
                                // Unfortunately, System.Reflection.Emit automatically emits
                                // a leave to the end of a finally block.  This is a problem
                                // if no code is following the try/finally block since we may
                                // jump to a point after the end of the method.
                                // As a workaround, we're always creating a return label in
                                // this case.
                                //

                                bool in_iterator = (CurrentAnonymousMethod != null) &&
                                        CurrentAnonymousMethod.IsIterator && InIterator;

                                if ((block != null) && block.IsDestructor) {
                                        // Nothing to do; S.R.E automatically emits a leave.
                                } else if (HasReturnLabel || (!unreachable && !in_iterator)) {
                                        if (ReturnType != null)
                                                ig.Emit (OpCodes.Ldloc, TemporaryReturn ());
                                        ig.Emit (OpCodes.Ret);
                                }
                        }

                        //
                        // Close pending helper classes if we are the toplevel
                        //
                        if (capture_context != null && capture_context.ParentToplevel == null)
                                capture_context.CloseAnonymousHelperClasses ();
                }

                /// <summary>
                ///   This is called immediately before emitting an IL opcode to tell the symbol
                ///   writer to which source line this opcode belongs.
                /// </summary>
                public void Mark (Location loc, bool check_file)
                {
                        if ((CodeGen.SymbolWriter == null) || loc.IsNull)
                                return;

                        if (check_file && (CurrentFile != loc.File))
                                return;

                        CodeGen.SymbolWriter.MarkSequencePoint (ig, loc.Row, loc.Column);
                }

                public void DefineLocalVariable (string name, LocalBuilder builder)
                {
                        if (CodeGen.SymbolWriter == null)
                                return;

                        CodeGen.SymbolWriter.DefineLocalVariable (name, builder);
                }

                public void BeginScope ()
                {
                        ig.BeginScope();

                        if (CodeGen.SymbolWriter != null)
                                CodeGen.SymbolWriter.OpenScope(ig);
                }

                public void EndScope ()
                {
                        ig.EndScope();

                        if (CodeGen.SymbolWriter != null)
                                CodeGen.SymbolWriter.CloseScope(ig);
                }

                /// <summary>
                ///   Returns a temporary storage for a variable of type t as 
                ///   a local variable in the current body.
                /// </summary>
                public LocalBuilder GetTemporaryLocal (Type t)
                {
                        LocalBuilder location = null;
                        
                        if (temporary_storage != null){
                                object o = temporary_storage [t];
                                if (o != null){
                                        if (o is ArrayList){
                                                ArrayList al = (ArrayList) o;
                                                
                                                for (int i = 0; i < al.Count; i++){
                                                        if (al [i] != null){
                                                                location = (LocalBuilder) al [i];
                                                                al [i] = null;
                                                                break;
                                                        }
                                                }
                                        } else
                                                location = (LocalBuilder) o;
                                        if (location != null)
                                                return location;
                                }
                        }
                        
                        return ig.DeclareLocal (t);
                }

                public void FreeTemporaryLocal (LocalBuilder b, Type t)
                {
                        if (temporary_storage == null){
                                temporary_storage = new Hashtable ();
                                temporary_storage [t] = b;
                                return;
                        }
                        object o = temporary_storage [t];
                        if (o == null){
                                temporary_storage [t] = b;
                                return;
                        }
                        if (o is ArrayList){
                                ArrayList al = (ArrayList) o;
                                for (int i = 0; i < al.Count; i++){
                                        if (al [i] == null){
                                                al [i] = b;
                                                return;
                                        }
                                }
                                al.Add (b);
                                return;
                        }
                        ArrayList replacement = new ArrayList ();
                        replacement.Add (o);
                        temporary_storage.Remove (t);
                        temporary_storage [t] = replacement;
                }

                /// <summary>
                ///   Current loop begin and end labels.
                /// </summary>
                public Label LoopBegin, LoopEnd;

                /// <summary>
                ///   Default target in a switch statement.   Only valid if
                ///   InSwitch is true
                /// </summary>
                public Label DefaultTarget;

                /// <summary>
                ///   If this is non-null, points to the current switch statement
                /// </summary>
                public Switch Switch;

                /// <summary>
                ///   ReturnValue creates on demand the LocalBuilder for the
                ///   return value from the function.  By default this is not
                ///   used.  This is only required when returns are found inside
                ///   Try or Catch statements.
                ///
                ///   This method is typically invoked from the Emit phase, so
                ///   we allow the creation of a return label if it was not
                ///   requested during the resolution phase.   Could be cleaned
                ///   up, but it would replicate a lot of logic in the Emit phase
                ///   of the code that uses it.
                /// </summary>
                public LocalBuilder TemporaryReturn ()
                {
                        if (return_value == null){
                                return_value = ig.DeclareLocal (ReturnType);
                                if (!HasReturnLabel){
                                        ReturnLabel = ig.DefineLabel ();
                                        HasReturnLabel = true;
                                }
                        }

                        return return_value;
                }

                /// <summary>
                ///   This method is used during the Resolution phase to flag the
                ///   need to define the ReturnLabel
                /// </summary>
                public void NeedReturnLabel ()
                {
                        if (current_phase != Phase.Resolving){
                                //
                                // The reason is that the `ReturnLabel' is declared between
                                // resolution and emission
                                // 
                                throw new Exception ("NeedReturnLabel called from Emit phase, should only be called during Resolve");
                        }
                        
                        if (!InIterator && !HasReturnLabel) 
                                HasReturnLabel = true;
                }

                //
                // Emits the proper object to address fields on a remapped
                // variable/parameter to field in anonymous-method/iterator proxy classes.
                //
                public void EmitThis (bool need_address)
                {
                        ig.Emit (OpCodes.Ldarg_0);
                        if (capture_context != null && CurrentAnonymousMethod != null){
                                ScopeInfo si = CurrentAnonymousMethod.Scope;
                                while (si != null){
                                        if (si.ParentLink != null)
                                                ig.Emit (OpCodes.Ldfld, si.ParentLink);
                                        if (si.THIS != null){
                                                if (need_address && TypeManager.IsValueType (si.THIS.FieldType))
                                                        ig.Emit (OpCodes.Ldflda, si.THIS);
                                                else
                                                        ig.Emit (OpCodes.Ldfld, si.THIS);
                                                break;
                                        }
                                        si = si.ParentScope;
                                }
                        } 
                }

                //
                // Emits the code necessary to load the instance required
                // to access the captured LocalInfo
                //
                public void EmitCapturedVariableInstance (LocalInfo li)
                {
                        if (capture_context == null)
                                throw new Exception ("Calling EmitCapturedContext when there is no capture_context");
                        
                        capture_context.EmitCapturedVariableInstance (this, li, CurrentAnonymousMethod);
                }

                public void EmitParameter (string name, bool leave_copy, bool prepared, ref LocalTemporary temp)
                {
                        capture_context.EmitParameter (this, name, leave_copy, prepared, ref temp);
                }

                public void EmitAssignParameter (string name, Expression source, bool leave_copy, bool prepare_for_load, ref LocalTemporary  temp)
                {
                        capture_context.EmitAssignParameter (this, name, source, leave_copy, prepare_for_load, ref temp);
                }

                public void EmitAddressOfParameter (string name)
                {
                        capture_context.EmitAddressOfParameter (this, name);
                }
                
                public Expression GetThis (Location loc)
                {
                        This my_this;
                        if (CurrentBlock != null)
                                my_this = new This (CurrentBlock, loc);
                        else
                                my_this = new This (loc);

                        if (!my_this.ResolveBase (this))
                                my_this = null;

                        return my_this;
                }
        }


        public abstract class CommonAssemblyModulClass : Attributable {
                protected CommonAssemblyModulClass ():
                        base (null)
                {
                }

                public void AddAttributes (ArrayList attrs)
                {
                        if (OptAttributes == null) {
                                OptAttributes = new Attributes (attrs);
                                return;
                        }
                        OptAttributes.AddAttributes (attrs);
                }

                public virtual void Emit (TypeContainer tc) 
                {
                        if (OptAttributes == null)
                                return;

                        EmitContext ec = new EmitContext (tc, Mono.CSharp.Location.Null, null, null, 0, false);
                        OptAttributes.Emit (ec, this);
                }
                
                protected Attribute ResolveAttribute (Type a_type)
                {
                        if (OptAttributes == null)
                                return null;

                        // Ensure that we only have GlobalAttributes, since the Search below isn't safe with other types.
                        if (!OptAttributes.CheckTargets (this))
                                return null;

                        EmitContext temp_ec = new EmitContext (RootContext.Tree.Types, Mono.CSharp.Location.Null, null, null, 0, false);
                        Attribute a = OptAttributes.Search (a_type, temp_ec);
                        if (a != null) {
                                a.Resolve (temp_ec);
                        }
                        return a;
                }
        }
                
        public class AssemblyClass : CommonAssemblyModulClass {
                // TODO: make it private and move all builder based methods here
                public AssemblyBuilder Builder;
                bool is_cls_compliant;
                bool wrap_non_exception_throws;

                public Attribute ClsCompliantAttribute;

                ListDictionary declarative_security;

                // Module is here just because of error messages
                static string[] attribute_targets = new string [] { "assembly", "module" };

                public AssemblyClass (): base ()
                {
                        wrap_non_exception_throws = true;
                }

                public bool IsClsCompliant {
                        get {
                                return is_cls_compliant;
                        }
                }

                public bool WrapNonExceptionThrows {
                        get {
                                return wrap_non_exception_throws;
                        }
                }

                public override AttributeTargets AttributeTargets {
                        get {
                                return AttributeTargets.Assembly;
                        }
                }

                public override bool IsClsComplianceRequired(DeclSpace ds)
                {
                        return is_cls_compliant;
                }

                public void Resolve ()
                {
                        ClsCompliantAttribute = ResolveAttribute (TypeManager.cls_compliant_attribute_type);
                        if (ClsCompliantAttribute != null) {
                                is_cls_compliant = ClsCompliantAttribute.GetClsCompliantAttributeValue (null);
                        }

#if NET_2_0
                        Attribute a = ResolveAttribute (TypeManager.runtime_compatibility_attr_type);
                        if (a != null) {
                                object val = a.GetPropertyValue ("WrapNonExceptionThrows");
                                if (val != null)
                                        wrap_non_exception_throws = (bool)val;
                        }
#endif
                }

                // fix bug #56621
                private void SetPublicKey (AssemblyName an, byte[] strongNameBlob) 
                {
                        try {
                                // check for possible ECMA key
                                if (strongNameBlob.Length == 16) {
                                        // will be rejected if not "the" ECMA key
                                        an.SetPublicKey (strongNameBlob);
                                }
                                else {
                                        // take it, with or without, a private key
                                        RSA rsa = CryptoConvert.FromCapiKeyBlob (strongNameBlob);
                                        // and make sure we only feed the public part to Sys.Ref
                                        byte[] publickey = CryptoConvert.ToCapiPublicKeyBlob (rsa);
                                        
                                        // AssemblyName.SetPublicKey requires an additional header
                                        byte[] publicKeyHeader = new byte [12] { 0x00, 0x24, 0x00, 0x00, 0x04, 0x80, 0x00, 0x00, 0x94, 0x00, 0x00, 0x00 };

                                        byte[] encodedPublicKey = new byte [12 + publickey.Length];
                                        Buffer.BlockCopy (publicKeyHeader, 0, encodedPublicKey, 0, 12);
                                        Buffer.BlockCopy (publickey, 0, encodedPublicKey, 12, publickey.Length);
                                        an.SetPublicKey (encodedPublicKey);
                                }
                        }
                        catch (Exception) {
                                Error_AssemblySigning ("The specified file `" + RootContext.StrongNameKeyFile + "' is incorrectly encoded");
                                Environment.Exit (1);
                        }
                }

                // TODO: rewrite this code (to kill N bugs and make it faster) and use standard ApplyAttribute way.
                public AssemblyName GetAssemblyName (string name, string output) 
                {
                        if (OptAttributes != null) {
                                foreach (Attribute a in OptAttributes.Attrs) {
                                        // cannot rely on any resolve-based members before you call Resolve
                                        if (a.ExplicitTarget == null || a.ExplicitTarget != "assembly")
                                                continue;

                                        // TODO: This code is buggy: comparing Attribute name without resolving is wrong.
                                        //       However, this is invoked by CodeGen.Init, when none of the namespaces
                                        //       are loaded yet.
                                        // TODO: Does not handle quoted attributes properly
                                        switch (a.Name) {
                                                case "AssemblyKeyFile":
                                                case "AssemblyKeyFileAttribute":
                                                case "System.Reflection.AssemblyKeyFileAttribute":
                                                        if (RootContext.StrongNameKeyFile != null) {
                                                                Report.SymbolRelatedToPreviousError (a.Location, a.Name);
                                                                Report.Warning (1616, 1, "Option `{0}' overrides attribute `{1}' given in a source file or added module",
                                    "keyfile", "System.Reflection.AssemblyKeyFileAttribute");
                                                        }
                                                        else {
                                                                string value = a.GetString ();
                                                                if (value != String.Empty)
                                                                        RootContext.StrongNameKeyFile = value;
                                                        }
                                                        break;
                                                case "AssemblyKeyName":
                                                case "AssemblyKeyNameAttribute":
                                                case "System.Reflection.AssemblyKeyNameAttribute":
                                                        if (RootContext.StrongNameKeyContainer != null) {
                                                                Report.SymbolRelatedToPreviousError (a.Location, a.Name);
                                                                Report.Warning (1616, 1, "Option `{0}' overrides attribute `{1}' given in a source file or added module",
                                                                        "keycontainer", "System.Reflection.AssemblyKeyNameAttribute");
                                                        }
                                                        else {
                                                                string value = a.GetString ();
                                                                if (value != String.Empty)
                                                                        RootContext.StrongNameKeyContainer = value;
                                                        }
                                                        break;
                                                case "AssemblyDelaySign":
                                                case "AssemblyDelaySignAttribute":
                                                case "System.Reflection.AssemblyDelaySignAttribute":
                                                        RootContext.StrongNameDelaySign = a.GetBoolean ();
                                                        break;
                                        }
                                }
                        }

                        AssemblyName an = new AssemblyName ();
                        an.Name = Path.GetFileNameWithoutExtension (name);

                        // note: delay doesn't apply when using a key container
                        if (RootContext.StrongNameKeyContainer != null) {
                                an.KeyPair = new StrongNameKeyPair (RootContext.StrongNameKeyContainer);
                                return an;
                        }

                        // strongname is optional
                        if (RootContext.StrongNameKeyFile == null)
                                return an;

                        string AssemblyDir = Path.GetDirectoryName (output);

                        // the StrongName key file may be relative to (a) the compiled
                        // file or (b) to the output assembly. See bugzilla #55320
                        // http://bugzilla.ximian.com/show_bug.cgi?id=55320

                        // (a) relative to the compiled file
                        string filename = Path.GetFullPath (RootContext.StrongNameKeyFile);
                        bool exist = File.Exists (filename);
                        if ((!exist) && (AssemblyDir != null) && (AssemblyDir != String.Empty)) {
                                // (b) relative to the outputed assembly
                                filename = Path.GetFullPath (Path.Combine (AssemblyDir, RootContext.StrongNameKeyFile));
                                exist = File.Exists (filename);
                        }

                        if (exist) {
                                using (FileStream fs = new FileStream (filename, FileMode.Open, FileAccess.Read)) {
                                        byte[] snkeypair = new byte [fs.Length];
                                        fs.Read (snkeypair, 0, snkeypair.Length);

                                        if (RootContext.StrongNameDelaySign) {
                                                // delayed signing - DO NOT include private key
                                                SetPublicKey (an, snkeypair);
                                        }
                                        else {
                                                // no delay so we make sure we have the private key
                                                try {
                                                        CryptoConvert.FromCapiPrivateKeyBlob (snkeypair);
                                                        an.KeyPair = new StrongNameKeyPair (snkeypair);
                                                }
                                                catch (CryptographicException) {
                                                        if (snkeypair.Length == 16) {
                                                                // error # is different for ECMA key
                                                                Report.Error (1606, "Could not sign the assembly. " + 
                                                                        "ECMA key can only be used to delay-sign assemblies");
                                                        }
                                                        else {
                                                                Error_AssemblySigning ("The specified file `" + RootContext.StrongNameKeyFile + "' does not have a private key");
                                                        }
                                                        return null;
                                                }
                                        }
                                }
                        }
                        else {
                                Error_AssemblySigning ("The specified file `" + RootContext.StrongNameKeyFile + "' does not exist");
                                return null;
                        }
                        return an;
                }

                void Error_AssemblySigning (string text)
                {
                        Report.Error (1548, "Error during assembly signing. " + text);
                }

                public override void ApplyAttributeBuilder (Attribute a, CustomAttributeBuilder customBuilder)
                {
                        if (a.Type.IsSubclassOf (TypeManager.security_attr_type) && a.CheckSecurityActionValidity (true)) {
                                if (declarative_security == null)
                                        declarative_security = new ListDictionary ();

                                a.ExtractSecurityPermissionSet (declarative_security);
                                return;
                        }

                        if (a.Type == TypeManager.assembly_culture_attribute_type) {
                                string value = a.GetString ();
                                if (value == null || value.Length == 0)
                                        return;

                                if (RootContext.Target == Target.Exe) {
                                        a.Error_AttributeEmitError ("The executables cannot be satelite assemblies, remove the attribute or keep it empty");
                                        return;
                                }
                        }

                        Builder.SetCustomAttribute (customBuilder);
                }

                public override void Emit (TypeContainer tc)
                {
                        base.Emit (tc);

                        if (declarative_security != null) {

                                MethodInfo add_permission = typeof (AssemblyBuilder).GetMethod ("AddPermissionRequests", BindingFlags.Instance | BindingFlags.NonPublic);
                                object builder_instance = Builder;

                                try {
                                        // Microsoft runtime hacking
                                        if (add_permission == null) {
                                                Type assembly_builder = typeof (AssemblyBuilder).Assembly.GetType ("System.Reflection.Emit.AssemblyBuilderData");
                                                add_permission = assembly_builder.GetMethod ("AddPermissionRequests", BindingFlags.Instance | BindingFlags.NonPublic);

                                                FieldInfo fi = typeof (AssemblyBuilder).GetField ("m_assemblyData", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.GetField);
                                                builder_instance = fi.GetValue (Builder);
                                        }

                                        object[] args = new object [] { declarative_security [SecurityAction.RequestMinimum],
                                                                                                  declarative_security [SecurityAction.RequestOptional],
                                                                                                  declarative_security [SecurityAction.RequestRefuse] };
                                        add_permission.Invoke (builder_instance, args);
                                }
                                catch {
                                        Report.RuntimeMissingSupport (Location.Null, "assembly permission setting");
                                }
                        }

#if NET_2_0
                        if (!OptAttributes.Contains (TypeManager.runtime_compatibility_attr_type, null)) {
                                ConstructorInfo ci = TypeManager.runtime_compatibility_attr_type.GetConstructor (TypeManager.NoTypes);
                                PropertyInfo pi = TypeManager.runtime_compatibility_attr_type.GetProperty ("WrapNonExceptionThrows");
                                Builder.SetCustomAttribute (new CustomAttributeBuilder (ci, new object [0], 
                                        new PropertyInfo [] { pi }, new object[] { true } ));
                        }
#endif
                }

                public override string[] ValidAttributeTargets {
                        get {
                                return attribute_targets;
                        }
                }
        }

        public class ModuleClass : CommonAssemblyModulClass {
                // TODO: make it private and move all builder based methods here
                public ModuleBuilder Builder;
                bool m_module_is_unsafe;

                public CharSet DefaultCharSet = CharSet.Ansi;
                public TypeAttributes DefaultCharSetType = TypeAttributes.AnsiClass;

                static string[] attribute_targets = new string [] { "module" };

                public ModuleClass (bool is_unsafe)
                {
                        m_module_is_unsafe = is_unsafe;
                }

                public override AttributeTargets AttributeTargets {
                        get {
                                return AttributeTargets.Module;
                        }
                }

                public override bool IsClsComplianceRequired(DeclSpace ds)
                {
                        return CodeGen.Assembly.IsClsCompliant;
                }

                public override void Emit (TypeContainer tc) 
                {
                        base.Emit (tc);

                        if (!m_module_is_unsafe)
                                return;

                        if (TypeManager.unverifiable_code_ctor == null) {
                                Console.WriteLine ("Internal error ! Cannot set unverifiable code attribute.");
                                return;
                        }
                                
                        Builder.SetCustomAttribute (new CustomAttributeBuilder (TypeManager.unverifiable_code_ctor, new object [0]));
                }
                
                public override void ApplyAttributeBuilder (Attribute a, CustomAttributeBuilder customBuilder)
                {
                        if (a.Type == TypeManager.cls_compliant_attribute_type) {
                                if (CodeGen.Assembly.ClsCompliantAttribute == null) {
                                        Report.Warning (3012, 1, a.Location, "You must specify the CLSCompliant attribute on the assembly, not the module, to enable CLS compliance checking");
                                }
                                else if (CodeGen.Assembly.IsClsCompliant != a.GetBoolean ()) {
                                        Report.SymbolRelatedToPreviousError (CodeGen.Assembly.ClsCompliantAttribute.Location, CodeGen.Assembly.ClsCompliantAttribute.GetSignatureForError ());
                                        Report.Error (3017, a.Location, "You cannot specify the CLSCompliant attribute on a module that differs from the CLSCompliant attribute on the assembly");
                                        return;
                                }
                        }

                        Builder.SetCustomAttribute (customBuilder);
                }

                /// <summary>
                /// It is called very early therefore can resolve only predefined attributes
                /// </summary>
                public void ResolveAttributes ()
                {
#if NET_2_0
                        Attribute a = ResolveAttribute (TypeManager.default_charset_type);
                        if (a != null) {
                                DefaultCharSet = a.GetCharSetValue ();
                                switch (DefaultCharSet) {
                                        case CharSet.Ansi:
                                        case CharSet.None:
                                                break;
                                        case CharSet.Auto:
                                                DefaultCharSetType = TypeAttributes.AutoClass;
                                                break;
                                        case CharSet.Unicode:
                                                DefaultCharSetType = TypeAttributes.UnicodeClass;
                                                break;
                                        default:
                                                Report.Error (1724, a.Location, "Value specified for the argument to 'System.Runtime.InteropServices.DefaultCharSetAttribute' is not valid");
                                                break;
                                }
                        }
#endif
                }

                public override string[] ValidAttributeTargets {
                        get {
                                return attribute_targets;
                        }
                }
        }
}