Script cleanup for standards-compliance (not going out of bounds on vectors).

I_POP is no longer considered a binary instruction because all other binary instructions expect the stack to have at least two elements - adding a manual check is kludgy
Added I_TAILCALL to accomodate indended optimizations

src/script/context.cpp

@@ -44,12 +44,15 @@ ScriptValueP Context::eval(const Script& script, bool useScope) {
 	try {
 		// Instruction pointer
 		const Instruction* instr = &script.instructions[0];
-		const Instruction* end   = &*script.instructions.end();
+		const Instruction* end   = instr + script.instructions.size();
 		
 		// Loop until we are done
 		while (instr < end) {
 			// Evaluate the current instruction
 			Instruction i = *instr++;
+			// If a scope is created, destroy it at end of block.
+			scoped_ptr<LocalScope> scope;
+
 			switch (i.instr) {
 				case I_NOP: break;
 				// Push a constant
@@ -59,7 +62,7 @@ ScriptValueP Context::eval(const Script& script, bool useScope) {
 				}
 				// Jump
 				case I_JUMP: {
-					instr = &script.instructions[i.data];
+					instr = &script.instructions[0] + i.data;
 					break;
 				}
 				// Conditional jump
@@ -67,7 +70,7 @@ ScriptValueP Context::eval(const Script& script, bool useScope) {
 					bool condition = *stack.back();
 					stack.pop_back();
 					if (!condition) {
-						instr = &script.instructions[i.data];
+						instr = &script.instructions[0] + i.data;
 					}
 					break;
 				}
@@ -98,7 +101,7 @@ ScriptValueP Context::eval(const Script& script, bool useScope) {
 						stack.push_back(val);
 					} else {
 						stack.erase(stack.end() - 2); // remove iterator
-						instr = &script.instructions[i.data];
+						instr = &script.instructions[0] + i.data;
 					}
 					break;
 				}
@@ -112,7 +115,7 @@ ScriptValueP Context::eval(const Script& script, bool useScope) {
 						stack.push_back(key);
 					} else {
 						stack.erase(stack.end() - 2); // remove iterator
-						instr = &script.instructions[i.data];
+						instr = &script.instructions[0] + i.data;
 					}
 					break;
 				}
@@ -123,9 +126,8 @@ ScriptValueP Context::eval(const Script& script, bool useScope) {
 				}
 				
 				// Function call
-				case I_CALL: {
-					// new scope
-					LocalScope local_scope(*this);
+				case I_CALL: scope.reset(new LocalScope(*this)); //new scope
+				case I_TAILCALL: {
 					// prepare arguments
 					for (unsigned int j = 0 ; j < i.data ; ++j) {
 						setVariable((Variable)instr[i.data - j - 1].data, stack.back());
@@ -203,6 +205,12 @@ ScriptValueP Context::eval(const Script& script, bool useScope) {
 					instrQuaternary(i.instr4, a, b, c, d);
 					break;
 				}
+				// Pop off stack
+				case I_POP: {
+					stack.pop_back();
+					break;
+				}
+
 				// Duplicate stack
 				case I_DUP: {
 					stack.push_back(stack.at(stack.size() - i.data - 1));
@@ -419,9 +427,6 @@ class ScriptCompose : public ScriptValue {
 
 void instrBinary (BinaryInstructionType  i, ScriptValueP& a, const ScriptValueP& b) {
 	switch (i) {
-		case I_POP:
-			// a = a;
-			break;
 		case I_MEMBER:
 			a = a->getMember(*b);
 			break;

src/script/dependency.cpp

@@ -169,7 +169,7 @@ ScriptValueP Context::dependencies(const Dependency& dep, const Script& script)
 				delete j;
 			}
 			
-			if (instr >= &*script.instructions.end()) break; // end of script
+			if (instr >= &script.instructions[0] + script.instructions.size()) break; // end of script
 			
 			// Analyze the current instruction
 			Instruction i = *instr++;
@@ -182,11 +182,11 @@ ScriptValueP Context::dependencies(const Dependency& dep, const Script& script)
 				}
 				// Jump
 				case I_JUMP: {
-					if (&script.instructions[i.data] >= instr) {
+					if ( &script.instructions[0] + i.data >= instr) {
 						// forward jump
 						// create jump record
 						Jump* jump = new Jump;
-						jump->target = &script.instructions[i.data];
+						jump->target = &script.instructions[0] + i.data;
 						jump->stack_top.assign(stack.begin() + stack_size, stack.end());
 						getBindings(scope, jump->bindings);
 						jumps.push(jump);
@@ -313,10 +313,6 @@ ScriptValueP Context::dependencies(const Dependency& dep, const Script& script)
 				}
 				// Simple instruction: binary
 				case I_BINARY: {
-					if (i.instr2 == I_POP) {
-						stack.pop_back();
-						continue;
-					}
 					ScriptValueP  b = stack.back(); stack.pop_back();
 					ScriptValueP& a = stack.back();
 					switch (i.instr2) {
@@ -356,6 +352,10 @@ ScriptValueP Context::dependencies(const Dependency& dep, const Script& script)
 					stack.push_back(stack.at(stack.size() - i.data - 1));
 					break;
 				}
+				// Pop value off stack
+				case I_POP: {
+					stack.pop_back();
+				}
 			}
 		}
 		

src/script/parser.cpp

@@ -534,10 +534,10 @@ void parseExpr(TokenIterator& input, Script& script, Precedence minPrec) {
 				expectToken(input, _("do"));							// do
 				if (with_key) {
 					script.addInstruction(I_SET_VAR, key);				//		set key_name
-					script.addInstruction(I_BINARY, I_POP);				//		 pop
+					script.addInstruction(I_POP);						//		 pop
 				}
 				script.addInstruction(I_SET_VAR, var);					//		set name
-				script.addInstruction(I_BINARY, I_POP);					//		 pop
+				script.addInstruction(I_POP);							//		 pop
 				parseOper(input, script, PREC_SET, I_BINARY, I_ADD);	// EEE;	add
 				script.addInstruction(I_JUMP, lblStart);				//		jump lbl_start
 				script.comeFrom(lblStart);								//		lbl_end:
@@ -650,7 +650,7 @@ void parseOper(TokenIterator& input, Script& script, Precedence minPrec, Instruc
 				// allow ; at end of expression without errors
 				break;
 			}
-			script.addInstruction(I_BINARY, I_POP); // discard result of first expression
+			script.addInstruction(I_POP); // discard result of first expression
 			parseOper(input, script, PREC_SET);
 		} else if (minPrec <= PREC_SET && token==_(":=")) {
 			// We made a mistake, the part before the := should be a variable name,
@@ -761,7 +761,7 @@ void parseOper(TokenIterator& input, Script& script, Precedence minPrec, Instruc
 			// newline functions as ;
 			// only if we don't match another token!
 			input.putBack();
-			script.addInstruction(I_BINARY, I_POP);
+			script.addInstruction(I_POP);
 			parseOper(input, script, PREC_SET);
 		} else {
 			input.putBack();

src/script/script.cpp

@@ -99,7 +99,11 @@ ScriptValueP Script::dependencies(Context& ctx, const Dependency& dep) const {
 static const unsigned int INVALID_ADDRESS = 0x03FFFFFF;
 
 unsigned int Script::addInstruction(InstructionType t) {
-	assert( t == I_JUMP || t == I_JUMP_IF_NOT || t == I_LOOP || t == I_LOOP_WITH_KEY);
+	assert( t == I_JUMP
+	     || t == I_JUMP_IF_NOT
+	     || t == I_LOOP
+	     || t == I_LOOP_WITH_KEY
+	     || t == I_POP);
 	Instruction i = {t, {INVALID_ADDRESS}};
 	instructions.push_back(i);
 	return getLabel() - 1;
@@ -179,7 +183,6 @@ String Script::dumpInstr(unsigned int pos, Instruction i) const {
 			break;
 		case I_BINARY:		ret += _("binary\t");
 			switch (i.instr2) {
-				case I_POP:			ret += _("pop");		break;
 				case I_ITERATOR_R:	ret += _("iterator_r");	break;
 				case I_MEMBER:		ret += _("member");		break;
 				case I_ADD:			ret += _("+");			break;
@@ -210,6 +213,8 @@ String Script::dumpInstr(unsigned int pos, Instruction i) const {
 			}
 			break;
 		case I_DUP:			ret += _("dup");				break;
+		case I_POP:			ret += _("pop");				break;
+		case I_TAILCALL:	ret += _("tailcall");			break;
 	}
 	// arg
 	switch (i.instr) {

src/script/script.hpp

@@ -43,6 +43,8 @@ enum InstructionType
 ,	I_TERNARY		= 14 ///< arg = 3ary instr : pop 3 values, apply a function, push the result
 ,	I_QUATERNARY	= 15 ///< arg = 4ary instr : pop 4 values, apply a function, push the result
 ,	I_DUP			= 16 ///< arg = int        : duplicate the k-from-top element of the stack
+,	I_POP			= 17 ///< arg = *          : pop the top value off the stack.
+,	I_TAILCALL		= 18 ///< arg = int, n*var : perform a tail call - like I_CALL, except faster
 };
 
 /// Types of unary instructions (taking one argument from the stack)
@@ -54,8 +56,7 @@ enum UnaryInstructionType
 
 /// Types of binary instructions (taking two arguments from the stack)
 enum BinaryInstructionType
-{	I_POP			///< Pop the top value of the stack
-,	I_ITERATOR_R	///< Make an iterator for a range (two integers)
+{	I_ITERATOR_R	///< Make an iterator for a range (two integers)
 ,	I_MEMBER		///< Member of an object
 // Arithmatic
 ,	I_ADD			///< add