Stack overflow detection wrapping for more entrypoints

I don't think this is exhaustive. This also adds an assert to detect when
js_check_stack_overflow is called outside a guard.

I'm trying to be conservative and wrap the entrypoints explicitly, but maybe it
would make sense to wrap JS_CallInternal instead?

quickjs.c

@@ -1589,6 +1589,8 @@ static inline uint8_t *js_get_stack_pointer(void)
 static inline BOOL js_check_stack_overflow(JSRuntime *rt, size_t alloca_size)
 {
     size_t size;
+
+    assert(stack_top != NULL);
     size = stack_top - js_get_stack_pointer();
     return unlikely((size + alloca_size) > rt->stack_size);
 }
@@ -18618,16 +18620,33 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValueConst func_obj,
 JSValue JS_Call(JSContext *ctx, JSValueConst func_obj, JSValueConst this_obj,
                 int argc, JSValueConst *argv)
 {
-    return JS_CallInternal(ctx, func_obj, this_obj, JS_UNDEFINED,
-                           argc, (JSValue *)argv, JS_CALL_FLAG_COPY_ARGV);
+    JSValue res;
+
+    if (stack_top == NULL) {
+        stack_top = js_get_stack_pointer();
+    }
+    res = JS_CallInternal(ctx, func_obj, this_obj, JS_UNDEFINED,
+                          argc, (JSValue *)argv, JS_CALL_FLAG_COPY_ARGV);
+    if (stack_top == js_get_stack_pointer()) {
+        stack_top = NULL;
+    }
+    return res;
 }
 
 static JSValue JS_CallFree(JSContext *ctx, JSValue func_obj, JSValueConst this_obj,
                            int argc, JSValueConst *argv)
 {
-    JSValue res = JS_CallInternal(ctx, func_obj, this_obj, JS_UNDEFINED,
+    JSValue res;
+
+    if (stack_top == NULL) {
+        stack_top = js_get_stack_pointer();
+    }
+    res = JS_CallInternal(ctx, func_obj, this_obj, JS_UNDEFINED,
                                   argc, (JSValue *)argv, JS_CALL_FLAG_COPY_ARGV);
     JS_FreeValue(ctx, func_obj);
+    if (stack_top == js_get_stack_pointer()) {
+        stack_top = NULL;
+    }
     return res;
 }