shithub: libmujs

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Improve stackidx function to return "undefined" for out-of-bounds accesses.

--- a/jsbuiltin.c

+++ b/jsbuiltin.c

@@ -28,7 +28,7 @@

 	if (jsR_loadscript(J, "(eval)", s))

 		jsR_error(J, "SyntaxError (eval)");

-	js_dup(J, 0); /* copy this */

+	js_copy(J, 0); /* copy this */

 	js_call(J, 0);

 	return 1;

 }

--- a/jsrun.c

+++ b/jsrun.c

@@ -40,15 +40,8 @@

 	return toint32(n);

 }

-/* Push and read stack values stack */

+/* Push values on stack */

-static int stackidx(js_State *J, int idx)

-{

-	if (idx < 0)

-		return top + idx;

-	return bot + idx;

-}

-

 static void js_pushvalue(js_State *J, js_Value v)

 {

 	stack[top] = v;

@@ -133,52 +126,55 @@

 	js_pushobject(J, jsR_newcfunction(J, v));

 }

+/* Read values from stack */

+

+static const js_Value *stackidx(js_State *J, int idx)

+{

+	static js_Value undefined = { JS_TUNDEFINED, { 0 } };

+	idx = idx < 0 ? top + idx : bot + idx;

+	if (idx < 0 || idx >= top)

+		return &undefined;

+	return stack + idx;

+}

+

 int js_isundefined(js_State *J, int idx)

 {

-	idx = stackidx(J, idx);

-	return stack[idx].type == JS_TUNDEFINED;

+	return stackidx(J, idx)->type == JS_TUNDEFINED;

 }

 int js_isstring(js_State *J, int idx)

 {

-	idx = stackidx(J, idx);

-	return stack[idx].type == JS_TSTRING;

+	return stackidx(J, idx)->type == JS_TSTRING;

 }

 js_Value js_tovalue(js_State *J, int idx)

 {

-	idx = stackidx(J, idx);

-	return stack[idx];

+	return *stackidx(J, idx);

 }

 int js_toboolean(js_State *J, int idx)

 {

-	idx = stackidx(J, idx);

-	return jsR_toboolean(J, &stack[idx]);

+	return jsR_toboolean(J, stackidx(J, idx));

 }

 double js_tonumber(js_State *J, int idx)

 {

-	idx = stackidx(J, idx);

-	return jsR_tonumber(J, &stack[idx]);

+	return jsR_tonumber(J, stackidx(J, idx));

 }

 const char *js_tostring(js_State *J, int idx)

 {

-	idx = stackidx(J, idx);

-	return jsR_tostring(J, &stack[idx]);

+	return jsR_tostring(J, stackidx(J, idx));

 }

 js_Object *js_toobject(js_State *J, int idx)

 {

-	idx = stackidx(J, idx);

-	return jsR_toobject(J, &stack[idx]);

+	return jsR_toobject(J, stackidx(J, idx));

 }

 js_Value js_toprimitive(js_State *J, int idx, int hint)

 {

-	idx = stackidx(J, idx);

-	return jsR_toprimitive(J, &stack[idx], hint);

+	return jsR_toprimitive(J, stackidx(J, idx), hint);

 }

 /* Stack manipulation */

@@ -188,13 +184,18 @@

 	top -= n;

 }

-void js_dup(js_State *J, int idx)

+void js_copy(js_State *J, int idx)

 {

-	idx = stackidx(J, idx);

-	stack[top] = stack[idx];

+	stack[top] = *stackidx(J, idx);

 	++top;

 }

+void js_dup(js_State *J)

+{

+	stack[top] = stack[top-1];

+	++top;

+}

+

 void js_dup2(js_State *J)

 {

 	stack[top] = stack[top-2];

@@ -446,7 +447,7 @@

 		opcode = *pc++;

 		switch (opcode) {

 		case OP_POP: js_pop(J, 1); break;

-		case OP_DUP: js_dup(J, -1); break;

+		case OP_DUP: js_dup(J); break;

 		case OP_DUP2: js_dup2(J); break;

 		case OP_ROT2: js_rot2(J); break;

 		case OP_ROT3: js_rot3(J); break;

@@ -467,7 +468,7 @@

 		case OP_TRUE: js_pushboolean(J, 1); break;

 		case OP_FALSE: js_pushboolean(J, 0); break;

-		case OP_THIS: js_dup(J, 0); break;

+		case OP_THIS: js_copy(J, 0); break;

 		case OP_GLOBAL: js_pushobject(J, J->G); break;

 		case OP_FUNDEC:

--- a/jsrun.h

+++ b/jsrun.h

@@ -44,6 +44,7 @@

 const char *js_tostring(js_State *J, int idx);

 void js_pop(js_State *J, int n);

-void js_dup(js_State *J, int idx);

+void js_dup(js_State *J);

+void js_copy(js_State *J, int idx);

 #endif