Hi,
Recently, I'm writing an application which uses JavaScriptCore to execute
javascript code. I just encountered a problem when using JSEvaluateScript
function to evaluate a piece of script. When executing the script, some
callbacks provided by my code will be called, but I found that the context
received by callbacks are different than the context I created and passed to
JSEvaluateScript function.
Attached is a test program.
Below is the output of this program on my system (ubuntu 8.04 64bit with
latest webkit svn):
Create context 0x7faf5d567e88, global object 0x7faf5d530000
InitializeCallback(ctx=0x7faf5d567e88, obj=0x7faf5d532400)
HasPropertyCallback(ctx=0x7faf50c4b048, obj=0x7faf5d532400, prop=prototype)
CallAsConstructorCallback(ctx=0x7faf50c4b0c0, obj=0x7faf5d532400)
InitializeCallback(ctx=0x7faf50c4b0c0, obj=0x7faf5d532440)
SetPropertyCallback(ctx=0x7faf50c4b048, obj=0x7faf5d532440, prop=prop1)
HasPropertyCallback(ctx=0x7faf50c4b048, obj=0x7faf5d532440, prop=prop1)
FinalizeCallback(obj=0x7faf5d532400)
FinalizeCallback(obj=0x7faf5d532440)
You can see that, the callback functions received several different context
pointers comparing to the one created at first beginning.
Is it an intend behavior or a bug of webkit? And how can I avoid or
workaround this problem?
Thanks a lot.
James Su
#include <cstdio>
#include <string>
#include <JavaScriptCore/JavaScript.h>
static std::string ConvertJSString(JSStringRef js_str) {
size_t bufsize = JSStringGetMaximumUTF8CStringSize(js_str);
char *buf = new char[bufsize];
buf[JSStringGetUTF8CString(js_str, buf, bufsize)] = 0;
std::string result(buf);
delete buf;
return result;
}
static void InitializeCallback(JSContextRef ctx, JSObjectRef object) {
printf("InitializeCallback(ctx=%p, obj=%p)\n", ctx, object);
}
static void FinalizeCallback(JSObjectRef object) {
printf("FinalizeCallback(obj=%p)\n", object);
}
static bool HasPropertyCallback(JSContextRef ctx,
JSObjectRef object,
JSStringRef property_name) {
printf("HasPropertyCallback(ctx=%p, obj=%p, prop=%s)\n",
ctx, object, ConvertJSString(property_name).c_str());
return false;
}
static JSValueRef GetPropertyCallback(JSContextRef ctx,
JSObjectRef object,
JSStringRef property_name,
JSValueRef* exception) {
printf("GetPropertyCallback(ctx=%p, obj=%p, prop=%s)\n",
ctx, object, ConvertJSString(property_name).c_str());
return NULL;
}
static bool SetPropertyCallback(JSContextRef ctx,
JSObjectRef object,
JSStringRef property_name,
JSValueRef value,
JSValueRef* exception) {
printf("SetPropertyCallback(ctx=%p, obj=%p, prop=%s)\n",
ctx, object, ConvertJSString(property_name).c_str());
return false;
}
// Only for custom registered classes.
static JSObjectRef CallAsConstructorCallback(JSContextRef ctx,
JSObjectRef constructor,
size_t argument_count,
const JSValueRef arguments[],
JSValueRef* exception) {
printf("CallAsConstructorCallback(ctx=%p, obj=%p)\n", ctx, constructor);
JSClassRef class_ref =
static_cast<JSClassRef>(JSObjectGetPrivate(constructor));
return JSObjectMake(ctx, class_ref, NULL);
}
static const JSClassDefinition
kClassDefinition = {
0, // version, shall be 0
kJSClassAttributeNone, // attributes
"Hello", // className, utf-8 encoded
NULL, // parentClass
NULL, // staticValues
NULL, // staticFunctions
InitializeCallback,
FinalizeCallback,
HasPropertyCallback,
GetPropertyCallback,
SetPropertyCallback,
NULL, // deleteProperty
NULL,
NULL,
CallAsConstructorCallback,
NULL, // hasInstance,
NULL, // convertToType
};
static const char kTestScript[] =
"var v1 = new Hello;\n"
"v1.prop1 = 123;\n"
"var v2 = v1.prop1;\n";
int main() {
JSGlobalContextRef context = JSGlobalContextCreate(NULL);
JSObjectRef global_object = JSContextGetGlobalObject(context);
printf("Create context %p, global object %p\n", context, global_object);
JSClassRef hello_class = JSClassCreate(&kClassDefinition);
JSObjectRef class_object =
JSObjectMake(context, hello_class, NULL);
JSObjectSetPrivate(class_object, hello_class);
JSStringRef class_name = JSStringCreateWithUTF8CString("Hello");
JSObjectSetProperty(context, global_object, class_name, class_object, 0, NULL);
JSStringRelease(class_name);
JSStringRef test_script =
JSStringCreateWithUTF8CString(kTestScript);
JSEvaluateScript(context, test_script, NULL, NULL, 0, NULL);
JSStringRelease(test_script);
JSGlobalContextRelease(context);
JSClassRelease(hello_class);
}
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