Improve debug lib consistency with lua 5.2

src/core/org/luaj/vm2/LuaClosure.java

@@ -124,6 +124,10 @@ public class LuaClosure extends LuaFunction {
 		return s_metatable; 
 	}
 	
+	public String tojstring() {
+		return "function: " + p.toString();
+	}
+	
 	public final LuaValue call() {
 		LuaValue[] stack = new LuaValue[p.maxstacksize];
 		for (int i = 0; i < p.numparams; ++i )
@@ -185,7 +189,8 @@ public class LuaClosure extends LuaFunction {
 		LuaValue[] k = p.k;
 		
 		// upvalues are only possible when closures create closures
-		UpValue[] openups = p.p.length>0? new UpValue[p.p.length]: null;
+		// TODO: use linked list.
+		UpValue[] openups = p.p.length>0? new UpValue[stack.length]: null;
 		
 		// debug wants args to this function
 		if (DebugLib.DEBUG_ENABLED && globals != null)

src/core/org/luaj/vm2/LuaError.java

@@ -47,8 +47,8 @@ public class LuaError extends RuntimeException {
 	protected Throwable cause;
 
 	public String getMessage() {
-		return (fileline != null? fileline + " ": "") 
+		return traceback != null? traceback:
-			+ (traceback != null? traceback: super.getMessage());
+			(fileline != null? fileline: "?:-1") + " " + super.getMessage();
 	}
 
 	/** Construct LuaError when a program exception occurs. 

src/core/org/luaj/vm2/LuaFunction.java

@@ -72,7 +72,10 @@ public class LuaFunction extends LuaValue {
 
 	public String tojstring() {
 		String s = getClass().getName();
-		return "function: " + s.substring(s.lastIndexOf('.')+1);
+		return "function: " + s.substring(Math.max(s.lastIndexOf('.'),s.lastIndexOf('$'))+1);
 	}
 
+	public LuaString strvalue() {
+		return valueOf(tojstring());
+	}
 }

src/core/org/luaj/vm2/LuaThread.java

@@ -307,9 +307,17 @@ public class LuaThread extends LuaValue {
 		public String traceback(int level) {
 			StringBuffer sb = new StringBuffer();
 			sb.append( "stack traceback:" );
-			for (LuaFunction f = null; (f = getFunction(level)) != null; ++level) {
+			CallFrame c = getCallFrame(level);
+			if (c != null) {
+				sb.append("\n\t");
+				sb.append( c.sourceline() );
+				sb.append( " in " );
+				while ( (c = getCallFrame(++level)) != null ) {
+					sb.append( c.tracename() );
 					sb.append( "\n\t" );
-				sb.append( f.tostring() );
+					sb.append( c.sourceline() );
+					sb.append( " in " );
+				}
 				sb.append( "main chunk" );
 			}
 			return sb.toString();
@@ -332,17 +340,16 @@ public class LuaThread extends LuaValue {
 
 	public static class CallFrame {
 		public LuaFunction f;
-		int pc, top;
+		public int pc;
+		int top;
 		Varargs v;
 		LuaValue[] stack;
+		boolean tail;
 		public void set(LuaClosure function, Varargs varargs, LuaValue[] stack) {
 			this.f = function;
 			this.v = varargs;
 			this.stack = stack;
-		}
+			this.tail = false;
-		public void print() {
-			// TODO Auto-generated method stub
-			
 		}
 		public void set(LuaFunction function) {
 			this.f = function;
@@ -356,7 +363,9 @@ public class LuaThread extends LuaValue {
 			this.pc = pc;
 			this.v = v;
 			this.top = top;
-			if (DebugLib.DEBUG_ENABLED && DebugLib.TRACE & f.isclosure())
+			if (f.checkclosure().p.code[pc] == Lua.OP_TAILCALL)
+				this.tail = true;
+			if (DebugLib.TRACE)
 				Print.printState(f.checkclosure(), pc, stack, top, v);
 		}
 		public Varargs getLocal(int i) {
@@ -377,34 +386,32 @@ public class LuaThread extends LuaValue {
 		}
 		public int currentline() {
 			if ( !f.isclosure() ) return -1;
-			int[] li = ((LuaClosure)f).p.lineinfo;
+			int[] li = f.checkclosure().p.lineinfo;
 			return li==null || pc<0 || pc>=li.length? -1: li[pc]; 
 		}
-		public LuaString[] getfunckind() {
-			if ( !f.isclosure() || pc<0 ) return null;
-			Prototype p = ((LuaClosure)f).p;
-			int stackpos = (p.code[pc] >> 6) & 0xff; 
-			return DebugLib.getobjname(p, pc, stackpos);
-		}
 		public String sourceline() {
 			if ( !f.isclosure() ) return f.tojstring();
-			String s = ((LuaClosure)f).p.source.tojstring();
+			String s = f.checkclosure().p.source.tojstring();
 			int line = currentline();
 			return (s.startsWith("@")||s.startsWith("=")? s.substring(1): s) + ":" + line;
 		}
 		public String tracename() {
-			LuaString[] kind = getfunckind();
+			LuaString[] kind = DebugLib.getfuncname(this);
 			if ( kind == null )
 				return "function ?";
 			return "function "+kind[0].tojstring();
 		}
 		public LuaString getlocalname(int index) {
 			if ( !f.isclosure() ) return null;
-			return ((LuaClosure)f).p.getlocalname(index, pc);
+			return f.checkclosure().p.getlocalname(index, pc);
 		}
 		public String tojstring() {
 			return tracename()+" "+sourceline();
 		}
+		public boolean istailcall() {
+			return tail;
+		}
+		
 	}
 		
 }

src/core/org/luaj/vm2/Print.java

@@ -410,8 +410,7 @@ public class Print extends Lua {
 						s.substring(0, 32).tojstring()+"...+"+(s.length()-32)+"b");					
 				break;
 			case LuaValue.TFUNCTION:
-				ps.print( ( v instanceof LuaClosure )?
+				ps.print( v.tojstring() );
-					((LuaClosure)v).p.toString(): v.tojstring() );
 				break;
 			case LuaValue.TUSERDATA:
 				Object o = v.touserdata();

src/core/org/luaj/vm2/lib/DebugLib.java

@@ -21,9 +21,8 @@
 ******************************************************************************/
 package org.luaj.vm2.lib;
 
-import java.lang.ref.WeakReference;
-
 import org.luaj.vm2.Globals;
+import org.luaj.vm2.LoadState.LuaCompiler;
 import org.luaj.vm2.Lua;
 import org.luaj.vm2.LuaBoolean;
 import org.luaj.vm2.LuaClosure;
@@ -34,11 +33,14 @@ import org.luaj.vm2.LuaNumber;
 import org.luaj.vm2.LuaString;
 import org.luaj.vm2.LuaTable;
 import org.luaj.vm2.LuaThread;
+import org.luaj.vm2.LuaThread.CallFrame;
 import org.luaj.vm2.LuaUserdata;
 import org.luaj.vm2.LuaValue;
-import org.luaj.vm2.Print;
 import org.luaj.vm2.Prototype;
 import org.luaj.vm2.Varargs;
+import org.luaj.vm2.lib.jme.JmePlatform;
+import org.luaj.vm2.lib.jse.JsePlatform;
+import org.luaj.vm2.luajc.LuaJC;
 
 /** 
  * Subclass of {@link LibFunction} which implements the lua standard {@code debug} 
@@ -90,9 +92,14 @@ public class DebugLib extends OneArgFunction {
 	private static final LuaString RETURN          = valueOf("return");  
 	private static final LuaString TAILRETURN      = valueOf("tail return");
 	private static final LuaString CONSTANT        = valueOf("constant");  
+	private static final LuaString FOR_ITERATOR    = valueOf("for iterator");
+	private static final LuaString METAMETHOD      = valueOf("metamethod");
 	
 	private static final LuaString FUNC            = valueOf("func");  
+	private static final LuaString ISTAILCALL      = valueOf("istailcall");  
+	private static final LuaString ISVARARG        = valueOf("isvararg");  
 	private static final LuaString NUPS            = valueOf("nups");  
+	private static final LuaString NPARAMS         = valueOf("nparams");  
 	private static final LuaString NAME            = valueOf("name");  
 	private static final LuaString NAMEWHAT        = valueOf("namewhat");  
 	private static final LuaString WHAT            = valueOf("what");  
@@ -110,9 +117,23 @@ public class DebugLib extends OneArgFunction {
 		globals.debuglib = this;
 		DEBUG_ENABLED = true;
 		LuaTable debug = new LuaTable();
-		env.set("debug", new debug());
+		debug.set("debug", new debug());
-		env.set("gethook", new gethook());
+		debug.set("gethook", new gethook());
-		env.set("sethook", new sethook());
+		debug.set("getinfo", new getinfo());
+		debug.set("getlocal", new getlocal());
+		debug.set("getmetatable", new getmetatable());
+		debug.set("getregistry", new getregistry());
+		debug.set("getupvalue", new getupvalue());
+		debug.set("getuservalue", new getuservalue());
+		debug.set("sethook", new sethook());
+		debug.set("setlocal", new setlocal());
+		debug.set("setmetatable", new setmetatable());
+		debug.set("setupvalue", new setupvalue());
+		debug.set("setuservalue", new setuservalue());
+		debug.set("traceback", new traceback());
+		debug.set("upvalueid", new upvalueid());
+		debug.set("upvaluejoin", new upvaluejoin());
+		env.set("debug", debug);
 		env.get("package").get("loaded").set("debug", debug);
 		return debug;
 	}
@@ -140,9 +161,74 @@ public class DebugLib extends OneArgFunction {
 		public Varargs invoke(Varargs args) {
 			int a=1;
 			LuaThread thread = args.isthread(a)? args.checkthread(a++): globals.running_thread; 
-			LuaValue func    = args.optfunction(a++, null);
+			LuaValue func = args.arg(a++);
-			String what       = args.optjstring(a++,"");
+			String what = args.optjstring(a++, "flnStu");
+			LuaThread.CallStack callstack = thread.callstack;
+
+			// find the stack info
+			LuaThread.CallFrame frame;
+			if ( func.isnumber() ) {
+				frame = callstack.getCallFrame(func.toint());
+				if (frame == null)
 					return NONE;
+				func = frame.f;
+			} else if ( func.isfunction() ) {
+				frame = callstack.findCallFrame(func);
+			} else {
+				return argerror(a-2, "function or level");
+			}
+
+			// start a table
+			LuaTable info = new LuaTable();
+			LuaClosure c = func.optclosure(null);
+			if (what.indexOf('S') >= 0) {
+				if (c != null) {
+					Prototype p = c.p;
+					info.set(WHAT, LUA);
+					info.set(SOURCE, p.source);
+					info.set(SHORT_SRC, valueOf(sourceshort(p)));
+					info.set(LINEDEFINED, valueOf(p.linedefined));
+					info.set(LASTLINEDEFINED, valueOf(p.lastlinedefined));
+				} else {
+					String shortName = func.tojstring();
+					LuaString name = LuaString.valueOf("[Java] " + shortName);
+					info.set(WHAT, JAVA);
+					info.set(SOURCE, name);
+					info.set(SHORT_SRC, valueOf(shortName));
+					info.set(LINEDEFINED, LuaValue.MINUSONE);
+					info.set(LASTLINEDEFINED, LuaValue.MINUSONE);
+				}
+			}
+			if (what.indexOf('l') >= 0) {
+				info.set( CURRENTLINE, valueOf(frame!=null? frame.currentline(): -1) );
+			}
+			if (what.indexOf('u') >= 0) {
+				info.set(NUPS, valueOf(c!=null? c.p.upvalues.length: 0));
+				info.set(NPARAMS, valueOf(c!=null? c.p.numparams: 0));
+				info.set(ISVARARG, valueOf(c!=null? c.p.is_vararg: 0));
+			}
+			if (what.indexOf('n') >= 0) {
+				if (frame != null) {
+					LuaString[] kind = getfuncname(frame);
+					info.set(NAME, kind!=null? kind[0]: QMARK);
+					info.set(NAMEWHAT, kind!=null? kind[1]: EMPTYSTRING);
+				}
+			}
+			if (what.indexOf('t') >= 0) {
+				info.set(ISTAILCALL, frame != null && frame.istailcall()? ONE: ZERO);
+			}
+			if (what.indexOf('L') >= 0) {
+				LuaTable lines = new LuaTable();
+				info.set(ACTIVELINES, lines);
+				CallFrame cf;
+				for (int l = 1; (cf=callstack.getCallFrame(l)) != null; ++l)
+					if (cf.f == func)
+						lines.insert(-1, valueOf(cf.currentline()));
+			}
+			if (what.indexOf('f') >= 0) {
+				info.set( FUNC, func );
+			}
+			return info;
 		}
 	}
 
@@ -151,9 +237,9 @@ public class DebugLib extends OneArgFunction {
 		public Varargs invoke(Varargs args) {
 			int a=1;
 			LuaThread thread = args.isthread(a)? args.checkthread(a++): globals.running_thread; 
-			LuaValue func    = args.optfunction(a++, null);
+			int level = args.checkint(a++);
-			LuaValue local   = args.checkvalue(a++);
+			int local = args.checkint(a++);
-			return thread.callstack.findCallFrame(func).getLocal(local.toint());
+			return thread.callstack.getCallFrame(level).getLocal(local);
 		}
 	}
 
@@ -225,32 +311,27 @@ public class DebugLib extends OneArgFunction {
 		public Varargs invoke(Varargs args) {
 			int a=1;
 			LuaThread thread = args.isthread(a)? args.checkthread(a++): globals.running_thread; 
-			LuaValue func    = args.optfunction(a++, null);
+			int level = args.checkint(a++);
-			LuaValue local   = args.checkvalue(a++);
+			int local = args.checkint(a++);
-			LuaValue value   = args.checkvalue(a++);
+			LuaValue value = args.arg(a++);
-			return thread.callstack.findCallFrame(func).setLocal(local.toint(), value);
+			return thread.callstack.getCallFrame(level).setLocal(local, value);
 		}
 	}
 
 	//	debug.setmetatable (value, table)
-	final class setmetatable extends VarArgFunction { 
+	final class setmetatable extends TwoArgFunction { 
-		public Varargs invoke(Varargs args) {
+		public LuaValue call(LuaValue value, LuaValue table) {
-			LuaValue object = args.arg(1);
+			LuaValue mt = table.opttable(null);
-			try {
+			switch ( value.type() ) {
-				LuaValue mt = args.opttable(2, null);
-				switch ( object.type() ) {
 				case TNIL:      LuaNil.s_metatable      = mt; break;
 				case TNUMBER:   LuaNumber.s_metatable   = mt; break;
 				case TBOOLEAN:  LuaBoolean.s_metatable  = mt; break;
 				case TSTRING:   LuaString.s_metatable   = mt; break;
 				case TFUNCTION: LuaFunction.s_metatable = mt; break;
 				case TTHREAD:   LuaThread.s_metatable   = mt; break;
-					default: object.setmetatable( mt );
+				default: value.setmetatable( mt );
-				}
-				return LuaValue.TRUE;
-			} catch ( LuaError e ) {
-				return varargsOf(FALSE, valueOf(e.toString()));
 			}
+			return value;
 		}
 	}
 
@@ -291,7 +372,7 @@ public class DebugLib extends OneArgFunction {
 			LuaThread thread = args.isthread(a)? args.checkthread(a++): globals.running_thread; 
 			String message = args.optjstring(a++, null);
 			int level = args.optint(a++,1);
-			String tb = thread.callstack.traceback(level-1);
+			String tb = thread.callstack.traceback(level);
 			return valueOf(message!=null? message+"\n"+tb: tb);
 		}
 	}
@@ -332,82 +413,6 @@ public class DebugLib extends OneArgFunction {
 		return null;
 	}
 	
-	
-	// ------------------- library function implementations -----------------
-	protected Varargs _getinfo(Varargs args, LuaValue level0func) {
-		int a=1;
-		LuaThread thread = args.isthread(a)? args.checkthread(a++): globals.running_thread; 
-		LuaValue func = args.arg(a++);
-		String what = args.optjstring(a++, "nSluf");
-		LuaThread.CallStack callstack = thread.callstack;
-
-		// find the stack info
-		LuaThread.CallFrame frame;
-		if ( func.isnumber() ) {
-			frame = callstack.getCallFrame(func.toint());
-		} else {
-			frame = callstack.findCallFrame(func);
-		}
-		if (frame == null)
-			return NIL;
-
-		// start a table
-		LuaTable info = new LuaTable();
-		LuaClosure c = frame.f.isclosure()? (LuaClosure) frame.f: null;
-		for (int i = 0, j = what.length(); i < j; i++) {
-			switch (what.charAt(i)) {
-				case 'S': {
-					if ( c != null ) {
-						Prototype p = c.p;
-						info.set(WHAT, LUA);
-						info.set(SOURCE, p.source);
-						info.set(SHORT_SRC, valueOf(sourceshort(p)));
-						info.set(LINEDEFINED, valueOf(p.linedefined));
-						info.set(LASTLINEDEFINED, valueOf(p.lastlinedefined));
-					} else {
-						String shortName = frame.f.tojstring();
-						LuaString name = LuaString.valueOf("[Java] "+shortName);
-						info.set(WHAT, JAVA);
-						info.set(SOURCE, name);
-						info.set(SHORT_SRC, valueOf(shortName));
-						info.set(LINEDEFINED, LuaValue.MINUSONE);
-						info.set(LASTLINEDEFINED, LuaValue.MINUSONE);
-					}
-					break;
-				}
-				case 'l': {
-					int line = frame.currentline();
-					info.set( CURRENTLINE, valueOf(line) );
-					break;
-				}
-				case 'u': {
-					info.set(NUPS, valueOf(c!=null? c.p.upvalues.length: 0));
-					break;
-				}
-				case 'n': {
-					LuaString[] kind = frame.getfunckind();
-					info.set(NAME, kind!=null? kind[0]: QMARK);
-					info.set(NAMEWHAT, kind!=null? kind[1]: EMPTYSTRING);
-					break;
-				}
-				case 'f': {
-					info.set( FUNC, frame.f );
-					break;
-				}
-				case 'L': {
-					LuaTable lines = new LuaTable();
-					info.set(ACTIVELINES, lines);
-					int line = frame.currentline();
-					if ( line >= 0 )
-						lines.set(1, valueOf(line));
-					break;
-				}
-			}
-		}
-		return info;
-	}
-
-
 	public static String sourceshort(Prototype p) {
 		String name = p.source.tojstring();
         if ( name.startsWith("@") || name.startsWith("=") )
@@ -417,12 +422,47 @@ public class DebugLib extends OneArgFunction {
         return name;
 	}
 	
-	// =======================================================
-	
 	static void lua_assert(boolean x) {
 		if (!x) throw new RuntimeException("lua_assert failed");
 	}	
 	
+	public static LuaString[] getfuncname(CallFrame frame) {
+		if (!frame.f.isclosure())
+			return new LuaString[] { frame.f.strvalue(), JAVA };
+		Prototype p = frame.f.checkclosure().p;
+		int pc = frame.pc;
+		int i = p.code[pc]; /* calling instruction */
+		LuaString tm;
+		switch (Lua.GET_OPCODE(i)) {
+			case Lua.OP_CALL:
+			case Lua.OP_TAILCALL: /* get function name */
+				return getobjname(p, pc, Lua.GETARG_A(i));
+			case Lua.OP_TFORCALL: /* for iterator */
+		    	return new LuaString[] { FOR_ITERATOR, FOR_ITERATOR};
+		    /* all other instructions can call only through metamethods */
+		    case Lua.OP_SELF:
+		    case Lua.OP_GETTABUP:
+		    case Lua.OP_GETTABLE: tm = LuaValue.INDEX; break;
+		    case Lua.OP_SETTABUP:
+		    case Lua.OP_SETTABLE: tm = LuaValue.NEWINDEX; break;
+		    case Lua.OP_EQ: tm = LuaValue.EQ; break;
+		    case Lua.OP_ADD: tm = LuaValue.ADD; break;
+		    case Lua.OP_SUB: tm = LuaValue.SUB; break;
+		    case Lua.OP_MUL: tm = LuaValue.MUL; break;
+		    case Lua.OP_DIV: tm = LuaValue.DIV; break;
+		    case Lua.OP_MOD: tm = LuaValue.MOD; break;
+		    case Lua.OP_POW: tm = LuaValue.POW; break;
+		    case Lua.OP_UNM: tm = LuaValue.UNM; break;
+		    case Lua.OP_LEN: tm = LuaValue.LEN; break;
+		    case Lua.OP_LT: tm = LuaValue.LT; break;
+		    case Lua.OP_LE: tm = LuaValue.LE; break;
+		    case Lua.OP_CONCAT: tm = LuaValue.CONCAT; break;
+		    default:
+		      return null;  /* else no useful name can be found */
+		}
+		return new LuaString[] { tm, METAMETHOD };
+	}
+	
 	// return StrValue[] { name, namewhat } if found, null if not
 	public static LuaString[] getobjname(Prototype p, int lastpc, int reg) {
 		int pc = lastpc; // currentpc(L, ci);
@@ -445,12 +485,12 @@ public class DebugLib extends OneArgFunction {
 			case Lua.OP_GETTABUP:
 			case Lua.OP_GETTABLE: {
 				int k = Lua.GETARG_C(i); /* key index */
-				int t = Lua.GETARG_Bx(i); /* table index */
+				int t = Lua.GETARG_B(i); /* table index */
 		        LuaString vn = (Lua.GET_OPCODE(i) == Lua.OP_GETTABLE)  /* name of indexed variable */
 	                    ? p.getlocalname(t + 1, pc)
 	                    : (t < p.upvalues.length ? p.upvalues[t].name : QMARK);
 				name = kname(p, k);
-				return new LuaString[] { name, vn.eq_b(ENV)? GLOBAL: FIELD };
+				return new LuaString[] { name, vn != null && vn.eq_b(ENV)? GLOBAL: FIELD };
 			}
 			case Lua.OP_GETUPVAL: {
 				int u = Lua.GETARG_B(i); /* upvalue index */

test/junit/org/luaj/vm2/ScriptDrivenTest.java

@@ -63,10 +63,10 @@ public class ScriptDrivenTest extends TestCase implements ResourceFinder {
 		default:
 		case JSE:
 		case LUAJIT:
-			globals = org.luaj.vm2.lib.jse.JsePlatform.standardGlobals();
+			globals = org.luaj.vm2.lib.jse.JsePlatform.debugGlobals();
 			break;
 		case JME:
-			globals = org.luaj.vm2.lib.jme.JmePlatform.standardGlobals();
+			globals = org.luaj.vm2.lib.jme.JmePlatform.debugGlobals();
 			break;
 		}
 	}
@@ -179,8 +179,6 @@ public class ScriptDrivenTest extends TestCase implements ResourceFinder {
 		if ( script == null )
 			fail("Could not load script for test case: " + name);
 		try {
-			// Use "stdin" instead of resource name so that output matches
-			// standard Lua.
 			switch ( this.platform ) {
 			case LUAJIT:
 				if ( nocompile ) {
@@ -190,7 +188,7 @@ public class ScriptDrivenTest extends TestCase implements ResourceFinder {
 					return LuaJC.getInstance().load( script, name, _G);
 				}
 			default:
-				return LoadState.load(script, "=stdin", "bt", _G);
+				return LoadState.load(script, "@"+name+".lua", "bt", _G);
 			}
 		} catch ( Exception e ) {
 			e.printStackTrace();

test/lua/coroutinelib.lua

@@ -80,6 +80,7 @@ local echo = function(msg,...)
 	return ... 
 end
 local echocr = function(...)
+	local arg = table.pack(...) 
 	echo('(echocr) first args', table.unpack(arg,1,arg.n)) 
 	local a = arg
 	while true do

test/lua/debuglib.lua

@@ -85,11 +85,11 @@ print( 'a.a='..tostring(a.a)..' a.b='..tostring(a.b)..' b.a='..tostring(b.a)..'
 local s1,x1,y1 = pcall( debug.getmetatable, a )
 local s2,x2,y2 = pcall( debug.setmetatable, a, mt )
 print( 'a.a='..tostring(a.a)..' a.b='..tostring(a.b)..' b.a='..tostring(b.a)..' b.b='..tostring(b.b)) 
-local s3,x3,y3 = pcall( debug.getmetatable, a )
+local s3,x3,y3 = pcall( debug.getmetatable, a ) print(type(s3), type(x3), type(y3), type(getmetatable(a)))
-local s4,x4,y4 = pcall( debug.getmetatable, b )
+local s4,x4,y4 = pcall( debug.getmetatable, b ) print(type(s4), type(x4), type(y4), type(getmetatable(b)))
-local s5,x5,y5 = pcall( debug.setmetatable, a, nil )
+local s5,x5,y5 = pcall( debug.setmetatable, a, nil ) print(type(s5), type(x5), type(y5), type(getmetatable(a)))
 print( 'a.a='..tostring(a.a)..' a.b='..tostring(a.b)..' b.a='..tostring(b.a)..' b.b='..tostring(b.b)) 
-local s6,x6,y6 = pcall( debug.getmetatable, a )
+local s6,x6,y6 = pcall( debug.getmetatable, a ) print(type(s6), type(x6), type(y6), type(getmetatable(a)))
 if not s1 then print( 's1 error', x1 ) end
 if not s2 then print( 's2 error', x2 ) end
 if not s3 then print( 's3 error', x3 ) end