I am trying to run some code from some time ago, after recompiling Lua for proper architecture, I am having some issues with the following line.
KillScript* script = (KillScript*)lua_tointeger(L, -1);
I am getting the following error on that line:
Cast of 'lua_integer' (aka'long') to 'KillScript' is disallowed with ARC.
Does anybody know why wouldn't this logic work?
Thanks!!
ARC -- automatic reference counting -- doesn't allow you to move between non-object reference types and object reference types. A lua_integeris a C scalar.
You can do some unsafe casting dance to keep ARC enabled, but I suspect you'll run into other issues.
If it is a standalone project, turn off ARC and try compiling. You'll likely run into other issues-- deprecation, etc... -- but at least you'll probably have relatively sane memory management behavior.
Related
In XCode (version 5.1.1 in my case), when you click Edit/Refactor/Convert to Objective-C ARC, what exactly is supposed to happen?
My goal here was to convert my old code to use ARC.
I basically set Objective-C Automatic Reference Counting to Yes, then I did the above to "refactor" my code. It failed and I ended up spending 5 hours commenting out anything with autorelease, retain, release etc... from my code.
When I finally got all that done, I was able to proceed with the Convert to Objective-C ARC operation, which ended up telling me that no changes to my code were necessary, which was true because I had done it all manually.
Is it supposed to do what I did manually, but automatically? Why didn't it?
By turning "Automatic Reference Counting" on manually you told the compiler that the project was already using ARC. Therefore, conversion did nothing - you told the compiler it was already converted.
Obviously all the non-ARC features you used were now errors and you had to fix them.
The normal method is that you do not change to Automatic Reference counting. The compiler will then check out your code, make sure that it can convert everything (it won't convert your code if the static analyser finds reference counting bugs, or when things are too complicated), you fix all the things that it refuses to convert, and once everything is Ok you convert everything.
And the answer to your question is "NO".
Basically, I have an IOS app that functioned without issue.
While following the instructions at http://docs.urbanairship.com/build/ios.html#ios-push-getting-started, I reached the "Register Your Device" section asking me to compile.
After attempting to build the code in xCode 5 I received the following error "#implementation UAPushSettingsAddTagViewController #synthesize of 'weak' property is only allowed in ARC or GC mode".
Note:ARC mode is not in use.
Search for "weak" in your project code and the libraries you include. Change it to a "assign"
Edit:
As #TaylorHalliday points out in his comment below, my answer was rather incomplete.
Changing weak properties to assign will get rid of compiler errors, but it will potentially cause memory management problems if you don't understand how to use manual reference counting.
Since you're using manual reference counting you will need to go through your code and make sure that you retain objects that you need to persist, and then release all owning references to objects when you are done with them. Explaining the details is beyond the scope of a forum post. I suggest you search on "About Memory Management" in the Xcode help system, and read the entire Advanced Memory Management Guide.
You should probably also run the Analyze tool on your project to look for possible memory management problems.
Better yet, convert your project to use ARC. It's much easier to avoid memory management problems when using ARC.
I got same error when I added these two files to my project. My project wasn't enabled for ARC. I had to remove these files first and then had to convert my project to ARC. Then adding these files caused no error.
I am using an fmod plugin for Unity3D. Compiling to Windows and OSX is fine because I can dynamically load the DLL/dylib.
The problem comes when I compile for iOS. I use
[DllImport("__Internal")]
Because iOS requires statically linked libraries. When I compile though I get a
SystemException: Duplicate native method found : FMOD_System_CreateSound. Please check your source carefully.
I am quite sure I don't duplicate the symbol. I think this might be due to the fact that Unity imports FMODs itself and that the two might be colliding... But if this is the case, I am surprised that FMOD_System_CreateSound is the first one to get caught. Is there a way around this? thx!
As always, I will be happy to provide any additional details!
Here is a sample project that will cause the error:
Sample Unity Project with FMod
EDIT:
The conflict was caused by iOS not allowing functions to have the same name even though they don't have the same signature. After removing the same-named functions (thus removing some FMOD features that I didn't need), I can compile to iOS, but as expected, I still get an error when Initializing because FMOD is already initialized by Unity.
Unity3d already has a limited version of FMOD that is bundled with it, which is causing the conflict you are seeing. Unfortunately, it doesn't seem possible to disable it at this time, so that you can use the full version of FMOD
In reference to your edit and after looking at the sample, it is true that you cannot have two methods of the same name as the compiler will not recognize which to link to.
The easy fix is to obviously name them differently.
As for the initialization, if you can access the FMOD that Unity 3D already created, then you don't have to reinitialize it.
I assume that a pointer to that object will be sufficient to remove the duplicate initialization. Hope this is clear.
I'm revisiting an an older project and converting to ARC, my first time through Xcode's conversion tool (Edit -> Refactor -> Convert to Objective-C ARC...), and I'm seeing a couple things that I'm not sure are real issues or red herrings somehow.
I get, as expected a big list of things that the tool finds that prevent it from completing, but:
Many (all?) instances of retain/release/autorelease appear to be flagged as errors e.g. "release is unavailable: not available in automatic reference counting mode". Am I really supposed to get rid of all these myself? I thought that's what the tool did.
In many of my classes, I'm seeing a bunch of errors that look like phantom parse/build errors that have nothing to do with ARC. E.g. in a simple class that apparently has no ARC-related issues, I'll get an "undeclared identifier" on some arbitrary method implementation, and then a bunch of "Parse error: expected }" at the end of the file, etc. These are not real-- the project builds fine, and I don't see any proximate cause or resolution for the errors.
There are "real" issues in the list as well (expected bridging issues that need to be explicitly clarified in code) but there are so many random errors of the above variety that it's hard to even find the signal in the noise. This seems wrong to me.
Am I misunderstanding what this tool is really doing? Apple's docs say this:
Xcode provides a tool that automates the mechanical parts of the ARC
conversion (such as removing retain and release calls) and helps you
to fix issues the migrator can’t handle automatically
Thanks.
The tool does not get rid of them for you, but simply adds retain/release code as need under the hood at the time of compile.
Those problems very well may go away when you get rid of old reference counting code.
EDIT: Further explanation:
In Xcode 4.2, in addition to syntax checking as you type, the new
Apple LLVM compiler makes it possible to offload the burden of manual
memory management to the compiler, introspecting your code to decide
when to release objects. Apple’s documentation describes ARC as
follows:
“Automatic Reference Counting (ARC) is a compiler-level feature that
simplifies the process of managing object lifetimes (memory
management) in Cocoa applications.”
In other words, ARC does not "strip" reference counting from your code, but rather does it on it's own under the hood. You no longer have to type release or retain or dealloc again. One thing the ARC needs to work is for it to do the reference counting entirely on it's own (with no user reference counting to "get in the way").
Took a long time to resolve, but both of these issues seemed to stem from some custom macros I was using. I had a macro for release-and-set-to-nil that I was using frequently, like this:
#define RELEASENIL(x) [(x) release]; \
(x) = nil;
I'm still not sure why, but for some reason, the ARC conversion tool didn't take this in stride, and choked on it, throwing the release warnings and the parse errors. (Some interaction with the preprocessor?) When I changed the macro to remove the release line, the conversion proceeded much more in line with my expectations.
And yes, it does of course remove the messages for you. (I'm answering my own question on the off chance that someone else ever has this issue.)
I'm getting the following exception when I run my application in Release mode from Visual C++.
Unhandled Exception:
System.AccessViolationException:
Attempted to read or write protected
memory. This is often an indication
that other memory is corrupt. at
_cexit() at .LanguageSupport._UninitializeDefaultDomain(Void
* cookie) at .LanguageSupport.UninitializeDefaultDomain()
at
.LanguageSupport.DomainUnload(Object
source, Eve ntArgs arguments) at
.ModuleUninitializer.SingletonDomainUnload(Objec
t source, EventArgs arguments)
This doesn't happen in Debug mode. Initially, I saw this exception on my home computer, but not work computer. When I continued to develop on my work computer, I ended up bumping into it.
Also, I found that when I added three const std::string variables the exception was thrown. If I removed then then all went well.
Another piece of information: I've found that turning off all the compiler optimizations in Release mode makes the exception go away
Something fishy is going on. Any ideas on how to track this down?
Thanks for the help,
Joe
Joe, you have a memory leak.
You're probably trying to use some memory that has been deleted.
See this article for common causes of memory leaks, and how to identify them, otherwise, search for "C++ memory profiler" + your compiler/platform, it'll give links to Memory profilers suitable for your compiler and platform, these will help track down the memory leak by watching how your program uses memory as it runs.
Hope this helps.
EDIT
How to track it down? This is off the top of my head, there may be better advice else where . . .
Find where the code crashes, it'll be when accessing the contents of some pointer (or deleting a pointer).
The problem is that that pointer has either a) never been assigned b) is already deleted.
Go through all references to pointers of that type, are they used in copy ctors/assignment operators?
If so, are it's contents being copied or just the pointer?
If just the pointer then is the containing class trying to delete the pointer? If so the first class to die will succeed, the second will throw an access violation.
If you don't explicitly code copy ctors and operator=, then you should hide them (declare private prototypes but don't implement them), this stops the compiler from generating default implementations for you.
When you hide them you'll get compiler errors everywhere they're being used, it might be that you can clean these up, or that you need to implement the copy ctor and operator= for each class.
I'm on vacation from tomorrow or two weeks, email me direct today (follow the link on my SO user page) if you've any questions on this.
Do you have any code that is #defined out for debuging in your code?
i.e.
#ifndef _DEBUG
//release only code such as liscensing code
#endif
That's one thing that could be causing the problem, and I've run into it before as well.
Another possibility is a VS issue (or whatever IDE you're using).
Try running the release .exe directly instead of through the develoment environment and see if you still have the same issue.
It's a while since I've done C++ "in anger" so to speak, so some (or indeed all) of what I say below may well be out of date.
Are you using managed C++? If not then it sounds like an uninitialised pointer. It used to be the case that all pointers were nulled in debug & I recall something about turning this behaviour off, but I can't remember the full details right now.
Are the strings overrunning their variables? Unlikely with std::string, but worth eliminating.
Couple of possibilities:
I would guess that you are reading/writing past local array end. In debug builds this may work, as memory is not tightly allocated. In release builds this is more likely to cause problems, depends on what is allocated right next to the array.
Another possibility is that you have an uninitialized pointer somewhere. VC default initializes local variables in debug mode, but not in release mode. Thus code like:
int* p;
if (p != NULL) { /* do something */ }
Typically fails on release mode.
The error message is strongly suggesting you have a memory issue, probably overwriting memory. These are hard to find, but you can find some possible solutions googling "visual c++ memory corruption tool".
The thing about memory corruption is that it's unpredictable. It doesn't necessarily have any consequences, and if it does they may not result in a crash. Crashing like that is good, because it informs you you've got a problem.
Fiddling with debug vs. release, adding or removing parts of code, changing optimization options and the like is unlikely to solve the problem. Even if it does, it's likely to crop up if any changes are made.
So, you've got a memory corruption problem. Those are almost always difficult to find, but there are tools. You need to fix that problem.
You might also look at your shop practices. Do you use less safe constructs (new arrays rather than vector<>, say)? Do you have coding standards to try to reduce risk? Do you have code reviews? Memory corruption can be insidious and damaging, and you want to avoid it as much as possible.
What your getting is a system exception from the OS. These are not handled because they are not C++ exception. However you can convert then into a C++ exception and catch them like a normal exception.
There is a great article here http://www.thunderguy.com/semicolon/2002/08/15/visual-c-exception-handling/ (page 3) that shows how to create a Windows Exception class that will catch the exception using the _set_se_translator method and throw a C++ exception. The great thing is you can get a stack from the EXCEPTION_RECORD structure, although your'll have to add that functionality to process the structure, but it will help narrow your search for that access violation.
I think the issue here is uninitialized local variable.
In Debug mode generally the variables get initialized and you don't get any exceptions.
But errors may occur in release mode because of this.
Try to look for uninitialized variable whose access may cause exception.
Suppose you have boolean local variable.
bool bRet;
In debug build bRet will get initailized to 0 and your code just works fine .
But in release it won't be 0 , it would be some random value and your code might be doing something based on bRet .It may later cause an exception because bRet value is wrong.