While using iOS 12, I encountered an issue:
I have a custom class named ClassA conforms NSCoding protocol, ClassA has a NSArray property, this array contains only one kind of custom ClassB's objcts, ClassB also conforms NSCoding protocol.
In my application, object of ClassA will be archived at one time and unarchived the next time. Everything works well under iOS 12.
Now with iOS 12, archive seems OK(archive will call ClassA and classB's encode function), while unarchive doesn't work properly: unarchive will call ClassA's encode function, but won't call ClassB's encode function(in iOS 11, it calls). The unarchived object of ClassB was totally wrong: it returns nil when called "isKindOfClass: [ClassB class]", typically it should return Yes or No.
I'm not sure if this issue was caused by iOS 12 system, anyone has an idea?
Related
Aside from recompiling rt.jar is there any way I can replace the currentTimeMillis() call with one of my own?
1# The right way to do it is use a Clock object and abstract time.
I know it but we'll be running code developed by an endless number of developers that have not implemented Clock or have made an implementation of their own.
2# Use a mock tool like JMockit to mock that class.
Even though that only works with Hotspot disabled -Xint and we have success using the code bellow it does not "persist" on external libraries. Meaning that you'd have to Mock it everywhere which, as the code is out of our control, is not feasible. All code under main() does return 0 milis (as from the example) but a new DateTime() will return the actual system millis.
#MockClass(realClass = System.class)
public class SystemMock extends MockUp<System> {
// returns 1970-01-01
#Mock public static long currentTimeMillis() { return 0; }
}
3# Re-declare System on start up by using -Xbootclasspath/p (edited)
While possible, and though you can create/alter methods, the one in question is declared as public static native long currentTimeMillis();. You cannot change it's declaration without digging into Sun's proprietary and native code which would make this an exercise of reverse engineering and hardly a stable approach.
All recent SUN JVM crash with the following error:
EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x00000, pid=4668, tid=5736
4# Use a custom ClassLoader (new test as suggested on the comments)
While trivial to replace the system CL using -Djava.system.class.loader JVM actually loads up the custom classLoader resorting to the default classLoader and System is not even pushed trough the custom CL.
public class SimpleClassLoader extends ClassLoader {
public SimpleClassLoader(ClassLoader classLoader) {
super(classLoader);
}
#Override
public Class<?> loadClass(String name) throws ClassNotFoundException {
return super.loadClass(name);
}
}
We can see that java.lang.System is loaded from rt.jar using java -verbose:class
Line 15: [Loaded java.lang.System from C:\jdk1.7.0_25\jre\lib\rt.jar]
I'm running out of options.
Is there some approach I'm missing?
You could use an AspectJ compiler/weaver to compile/weave the problematic user code, replacing the calls to java.lang.System.currentTimeMillis() with your own code. The following aspect will just do that:
public aspect CurrentTimeInMillisMethodCallChanger {
long around():
call(public static native long java.lang.System.currentTimeMillis())
&& within(user.code.base.pckg.*) {
return 0; //provide your own implementation returning a long
}
}
I'm not 100% sure if I oversee something here, but you can create your own System class like this:
public static class System {
static PrintStream err = System.err;
static InputStream in = System.in;
static PrintStream out = System.out;
static void arraycopy(Object src, int srcPos, Object dest, int destPos, int length) {
System.arraycopy(src, srcPos, dest, destPos, length);
}
// ... and so on with all methods (currently 26) except `currentTimeMillis()`
static long currentTimeMillis() {
return 4711L; // Your application specific clock value
}
}
than import your own System class in every java file. Reorganize imports in Eclipse should do the trick.
And than all java files should use your applicatikon specific System class.
As I said, not a nice solution because you will need to maintain your System class whenever Java changes the original one. Also you must make sure, that always your class is used.
As discussed in the comments, it is possible that option #3 in the original question has actually worked, successfully replacing the default System class.
If that is true, then application code which calls currentTimeMillis() will be calling the replacement, as expected.
Perhaps unexpectedly, core classes like java.util.Timer would also get the replacement!
If all of the above are true, then the root cause of the crash could be the successful replacement of the System class.
To test, you could instead replace System with a copy that is functionally identical to the original to see if the crashes disappear.
Unfortunately, if this answer turns out to be correct, it would seem that we have a new question. :) It might go like this:
"How do you provide an altered System.currentTimeMillis() to application classes, but leave the default implementation in place for core classes?"
i've tried using javassist to remove the native currentTimeMills, add a pure java one and load it using bootclasspath/p, but i got the same exception access violation as you did. i believe that's probably because of the native method registerNatives that's called in the static block but it's really too much to disassemble the native library.
so, instead of changing the System.currentTimeMills, how about changing the user code? if the user code already compiled (you don't have source code), we can use tools like findbugs to identify the use of currentTimeMillis and reject the code (maybe we can even replace the call to currentTimeMills with your own implementation).
I have updated my xcode 8 and running an old app which has been created in 7.3 by convering the swift codes in swift 3. But I am getting the message in log window as below:
objc[19295]: Class PLBuildVersion is implemented in both /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/System/Library/PrivateFrameworks/AssetsLibraryServices.framework/AssetsLibraryServices (0x118365910) and /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/System/Library/PrivateFrameworks/PhotoLibraryServices.framework/PhotoLibraryServices (0x11818f210). One of the two will be used. Which one is undefined.
activity started
why its happening ?
You have a class PLBuildVersion declared in your framework AssetsLibraryServices as well as in PhotoLibraryServices. Because class names are unique Xcode tells you that it will take one of those class declarations, but that it'll keep it a surprise, which one that is. ;)
Luckily, you don't have to be concerned because both classes should be the same.
I have a custom grid control that inherits from TGrid called TFmGrid. This control was working fine in Rad Studio 10 Seattle Update One. I recently upgraded to 10.1 Berlin and started noticing this error message showing up on my TFmGrid controls both when I run the application and in the designer:
A descendant of TStyledPresentationProxy has not been registered for class TFmGrid. Maybe it is necessary to add the FMX.Grid.Style module to the uses section
The image below shows how the error message shows up on my grid controls:
I started by doing as the message suggests, and adding #include <FMX.Grid.Style.hpp> to the header file of my TFmGrid control, however this seems to have done nothing.
So as far as trying to register a decendant of TStyledPresentationProxy I am not exactly sure where to start. I found this documentation about a method which:
Attempts to register the presentation proxy class with the specified name or the specified combination of control class and control type.
So I assume I need to use this method or at least something similar, but I don't understand how I am supposed to go about calling this method.
But then that brings up the question of WHERE do I call this code?
My custom control has a method in its namespace called Register() which I believe was autogenerated by the IDE when the control was created:
namespace Fmgridu
{
void __fastcall PACKAGE Register()
{
TComponentClass classes[1] = {__classid(TFmGrid)};
RegisterComponents(L"Kalos FM Controls", classes, 0);
}
}
Do I need to call something in there to register a decendant of TStyledPresentationProxy? What is the proper way to go about this?
Just override virtual method DefinePresentationName in you TfmGrid and return name of presentation name for grid:
function TfmGrid.DefinePresentationName: string;
begin
Result := 'Grid-' + GetPresentationSuffix;
end;
Fm registers presentation by string name and uses class name for it, so if you create new component (based on existed) you automatically change classname, so system cannot find presentation for you. There are two solution:
Said that you will use presentation from TGrid (DefinePresentationName)
Register existed presentation for you class (look at the initialization section of FMX.Grid.Style.pas)
P.S. Year ago i wrote article about it in common eNew approach of development of FireMonkey control “Control – Model – Presentation”. Part 1 I hope it will help you
It's simple :
Just put "StyleBook" component to your form
I had the same issue with a test component I was developing.
Complementing Yaroslav Brovin's speech, I solved the problem by adding the class register in the initialization and finalization clauses at the end of the unit, like this:
initialization
TPresentationProxyFactory.Current.Register(<COMPONENT CLASSNAME HERE>, TControlType.Styled, TStyledPresentationProxy<TStyledGrid>);
finalization
TPresentationProxyFactory.Current.Unregister(<COMPONENT CLASSNAME HERE>, TControlType.Styled, TStyledPresentationProxy<TStyledGrid>);
In my case looks like this:
initialization
TPresentationProxyFactory.Current.Register(TSGrid, TControlType.Styled, TStyledPresentationProxy<TStyledGrid>);
finalization
TPresentationProxyFactory.Current.Unregister(TSGrid, TControlType.Styled, TStyledPresentationProxy<TStyledGrid>);
PS: Don't forget to declare the FMX.Presentation.Factory,
FMX.Presentation.Style and FMX.Grid.Style units in the uses clause
I'm trying to get my feet wet with ASIO and thought a good first project would be a simple web crawler: download an html page, find the links in it, download all the links.
I have tried modifying the ASIO http client example to use enable_shared_from_this instead of a raw pointer so that I can spawn new async task from within the handler of the previous task without having to worry about the resources getting deleted in the middle of my work.
The problems start when I tried to subclass my client to handle different pages in different ways. The compiler complains that the type of the shared_ptr doesn't match the type of this.
Does anybody know how this is solved? I haven't been able to figure it out by myself.
This is unrelated to Asio.
If you inherited a base class from enable_shared_from_this, but need it in the derived one, use boost::static_pointer_cast:
struct base : enable_shared_from_this<base>
{
};
struct derived : base
{
shared_ptr<derived> shared_from_derived()
{
return static_pointer_cast<derived>(shared_from_this());
}
};
I've successfully loaded a C++ plugin using a custom plugin loader class. Each plugin has an extern "C" create_instance function that returns a new instance using "new".
A plugin is an abstract class with a few non-virtual functions and several protected variables(std::vector refList being one of them).
The plugin_loader class successfully loads and even calls a virtual method on the loaded class (namely "std::string plugin::getName()".
The main function creates an instance of "host" which contains a vector of reference counted smart pointers, refptr, to the class "plugin". Then, main creates an instance of plugin_loader which actually does the dlopen/dlsym, and creates an instance of refptr passing create_instance() to it. Finally, it passes the created refptr back to host's addPlugin function. host::addPlugin successfully calls several functions on the passed plugin instance and finally adds it to a vector<refptr<plugin> >.
The main function then subscribes to several Apple events and calls RunApplicationEventLoop(). The event callback decodes the result and then calls a function in host, host::sendToPlugin, that identifies the plugin the event is intended for and then calls the handler in the plugin. It's at this point that things stop working.
host::sendToPlugin reads the result and determines the plugin to send the event off to.
I'm using an extremely basic plugin created as a debugging plugin that returns static values for every non-void function.
Any call on any virtual function in plugin in the vector causes a bad access exception. I've tried replacing the refptrs with regular pointers and also boost::shared_ptrs and I keep getting the same exception. I know that the plugin instance is valid as I can examine the instance in Xcode's debugger and even view the items in the plugin's refList.
I think it might be a threading problem because the plugins were created in the main thread while the callback is operating in a seperate thread. I think things are still running in the main thread judging by the backtrace when the program hits the error but I don't know Apple's implementation of RunApplicationEventLoop so I can't be sure.
Any ideas as to why this is happening?
class plugin
{
public:
virtual std::string getName();
protected:
std::vector<std::string> refList;
};
and the pluginLoader class:
template<typename T> class pluginLoader
{
public: pluginLoader(std::string path);
// initializes private mPath string with path to dylib
bool open();
// opens the dylib and looks up the createInstance function. Returns true if successful, false otherwise
T * create_instance();
// Returns a new instance of T, NULL if unsuccessful
};
class host
{
public:
addPlugin(int id, plugin * plug);
sendToPlugin(); // this is the problem method
static host * me;
private:
std::vector<plugin *> plugins; // or vector<shared_ptr<plugin> > or vector<refptr<plugin> >
};
apple event code from host.cpp;
host * host::me;
pascal OSErr HandleSpeechDoneAppleEvent(const AppleEvent *theAEevt, AppleEvent *reply, SRefCon refcon) {
// this is all boilerplate taken straight from an apple sample except for the host::me->ae_callback line
OSErr status = 0;
Result result = 0;
// get the result
if (!status) {
host::me->ae_callback(result);
}
return status;
}
void host::ae_callback(Result result) {
OSErr err;
// again, boilerplate apple code
// grab information from result
if (!err)
sendToPlugin();
}
void host::sendToPlugin() {
// calling *any* method in plugin results in failure regardless of what I do
}
EDIT: This is being run on OSX 10.5.8 and I'm using GCC 4.0 with Xcode. This is not designed to be a cross platform app.
EDIT: To be clear, the plugin works up until the Apple-supplied event loop calls my callback function. When the callback function calls back into host is when things stop working. This is the problem I'm having, everything else up to that point works.
Without seeing all of your code it isn't going to be easy to work out exactly what is going wrong. Some things to look at:
Make sure that the linker isn't throwing anything away. On gcc try the compile options -Wl -E -- we use this on Linux, but don't seem to have found a need for it on the Macs.
Make sure that you're not accidentally unloading the dynamic library before you've finished with it. RAII doesn't work for unloading dynamic libraries unless you also stop exceptions at the dynamic library border.
You may want to examine our plug in library which works on Linux, Macs and Windows. The dynamic loading code (along with a load of other library stuff) is available at http://svn.felspar.com/public/fost-base/trunk/
We don't use the dlsym mechanism -- it's kind of hard to use properly (and portably). Instead we create a library of plugins by name and put what are basically factories in there. You can examine how this works by looking at the way that .so's with test suites can be dynamically loaded. An example loader is at http://svn.felspar.com/public/fost-base/trunk/fost-base/Cpp/fost-ftest/ftest.cpp and the test suite registration is in http://svn.felspar.com/public/fost-base/trunk/fost-base/Cpp/fost-test/testsuite.cpp The threadsafe_store holds the factories by name and the suite constructor registers the factory.
I completely missed the fact that I was calling dlclose in my plugin_loader's dtor and for some reason the plugins were getting destructed between the RunApplicatoinEventLoop call and the call to sendToPlugin. I removed dlclose and things work now.