I received a device with an SDK (*.h *.a files) and built a small app with it.
Now I received a new SDK that does almost the same operation and the *.h file is identical to the first sdk.
The first SDK is used to do some measurements and the second does it differently. I would like to compare the results.
The question is: Can I integrate both sdk in the same app? What do I need to do?
I hope I was clear enough. If any more information is needed I'll be happy to supply it.
As far as my understanding the answer is NO.
The linker needs to setup function pointers during the linking process. If the header file is the same, that also implies the signature of the functions were the same. There's no way for the linker to differentiate the function signature and setup different function pointers for the resulting binary.
Related
Out of educational purposes I'm trying to use Eigen in my pet project. In order to speed the math I included macro EIGEN_USE_BLAS which activates use of blas library.
But I encountered an issue when I tried to upload my project to Testflight. The Apple response to that was:
ITMS-90338: Non-public API usage - The app references non-public
symbols in My-Project: _saxpy_, _sgemm_, _sgemv_, _strmm_,
_strmv_. If method names in your source code match the private Apple
APIs listed above, altering your method names will help prevent this
app from being flagged in future submissions. In addition, note that
one or more of the above APIs may be located in a static library that
was included with your app. If so, they must be removed. For further
information, visit the Technical Support Information at
http://developer.apple.com/support/technical/
I know that Apple has blas library as a part of Accelerate.framework and it should be use strictly through Accelerate API. But the thing is that Eigen also has their own blas included in their source and the library actually has no intention of using Accelerate.framework private guts. So that is why Apple asks me to rename those functions or remove them completely in order to get rid of that inconvenience.
But I'm not even sure that it is possible to do - to tune Eigen and its blas to use alternative names.
Is there maybe a way to solve that issue in some efficient manner? Or maybe I don't know something about Eigen usage in iOS environment?
I was lucky to figure out the problem with few tips from my fellow colleagues and a strong will to get the job done, and now I want to share with you my conclusions.
The problem: Eigen doesn't have BLAS binary provided, it only has it's headers. And when one uses EIGEN_USE_BLAS macro and it actually works, that means that Apple is linking Eigen BLAS functions to their binary - BLAS binary which is a part of Accelerate.framework. The trickiest part is that your project doesn't necessarily should have Accelerate.framework inside. XCode will add necessary files automatically and of course it won't bother to tell you that.
What's weird for me the most here is that using "naked" BLAS provided by Apple's Accelerate.framework is a clear violation because it's private API. So... from my perspective it's kind of XCode violates this rule without my intention and tells me nothing about it. Strange...
So, in order to fix it, you need to build BLAS or OpenBLAS binary (I have built OpenBLAS), add it to the project and link through Other linker flags in Build settings. After that the error is gone and you're able to upload your build to Testflight.
In order to save you some time in building OpenBLAS for iOS, I will leave you few links. I think those would be enough:
http://www.programmersought.com/article/2638161057/ - very clear tutorial on how to build OpenBLAS
https://github.com/xianyi/OpenBLAS/tree/release-0.2.21 - source code of the library
https://github.com/xianyi/OpenBLAS/issues/1531 - discussion where you can find solutions to problems you might encounter
What I found the most confusing part of this whole story is the message from Apple. Here's another copy of that:
ITMS-90338: Non-public API usage - The app references non-public
symbols in My-Project: saxpy, sgemm, sgemv, strmm, strmv. If
method names in your source code match the private Apple APIs listed
above, altering your method names will help prevent this app from
being flagged in future submissions. In addition, note that one or
more of the above APIs may be located in a static library that was
included with your app. If so, they must be removed. For further
information, visit the Technical Support Information at
http://developer.apple.com/support/technical/
I'm not a native English speaker but I feel pretty confident to say that this text is a non-sense and has absolutely nothing to do with the solving of the actual problem.
It says absolutely nothing about the fact that private API was linked to my code and that is the problem. And that I need to provide my own backend for those functions in order to make error disappear. It says about names matching and that altering my names will help to solve the problem, when it clearly will not in my case.
I hope Apple will bring more clarity into this problem and that errors descriptions will have more sense in the future.
My goal is to build a swift iOS framework which uses two other frameworks (included as separate projects) and which shouldn't reveal the source code after built.
Is there some text/guide/documentation which would explain and navigate me through the process of building such a framework properly and correctly?
I built framework with aggregate target adding and linking frameworks on which my custom framework is dependent using run script as indicated here. I was able to add built of my custom framework to my custom app, together with other two dependencies (again as a separate projects), and run it on the device. However, I am not convinced by the correctness of my custom framework built.
Moreover, I was not able to upload the archive to the Appstore due to the various errors of "Unsupported architectures...", "CFBundleIdentifier Collision...", "Invalid Bundle...", "Invalid Binary" and so on. After sorting these errors out according to the various stackoverflow answers and installing the app from the TestFlight, the app crashed after launch and wasn't working at all.
I was checking various blog posts, stackoverflow questions/answers and Apple Framework Programming Guide but nothing gave me comprehensive understanding on building custom framework under conditions described above.
Everything I did was just following step-by-step tutorials without explanation of the purpose of the steps. I am sure I am missing the basics. Could you please help me and give me some guides?
I can understand you frustration. I, a while ago too searched probably for many documents on how to write a framework correctly but like you I also didn't find anything really that satisfying. From my own experiences I can give a couple of advices.
NO External Libraries
In my opinion DO NOT use external libraries in your own framework. I don't really know what your frameworks purpose is but most of the stuff you want to do can be done without using external libraries. Depending on other libraries is not a good idea especially if its a framework you are working on. Anytime these libraries get updated or even worse if they don't you will have to wait for them to be updated or find another library.So rather than this happening later on I think its better if you do it from the start. So loose the external libraries.
Universal Framework Binary
Second one is pretty easy. Generating a universal framework. I suggest you don't use a script. Most of the scripts I found were either outdated or they didn't work at all. Later on I found out that actually it was pretty easy to generate one on your own. You can do this by building your project once for a real device and one for the simulator.Then you can generate a universal binary by using the command lipo -create "Your simulator executable path" "your iOS device executable path" -output "your framework name". What this does is that it combines your two executable files and generates a universal one. Then you can just go and copy your simulator documents from the modules file and paste them in you iphoneos modules file. I am going to share a link were you can go through the walkthrough yourself. https://medium.com/wireless-registry-engineering/create-a-universal-fat-swift-framework-b7409bbfa18f
Use Objective-C(If you can)
This one is bit of a tricky one unless you know objective-c. What I would recommend is that you implement your framework using Objective-C and writing a swift wrapper around it. I would not have said this if you were creating an iOS app but in case of a framework I still think you should go for objective-c. This is because Objective-c has been around for over 30 years and most of the very old apps are in objective-c. If you want your framework to easily be used by older apps coded in objective-c I recommend you go with it. I have read tons of posts on how people have problems trying to use frameworks written in swift in their objective-c apps. Swift will be the first and probably only choice in the near future but not just yet. On the plus side if you still haven't you will have learnt Objective-C which will give definitely give you a better understanding on how things work. It will be challenging but I promise you it will be worth your while .I have a good read on this which you can checkout yourself. https://academy.realm.io/posts/altconf-conrad-kramer-writing-iOS-sdk/
Naming Conventions
This is a pretty straight forward one. I suggest you stick to apples naming conventions. This is because you will be sharing your code this time and people will look for familiarity when trying to integrate your framework. This will make your code easier to understand. You can check out these two links for more info.https://github.com/raywenderlich/objective-c-style-guide (obj-c) https://github.com/raywenderlich/swift-style-guide (swift)
Access Control
This in my opinion is an important one. When working on you framework think before you implement a class or a function. Consider if you would like someone else to be able to use that part of your code. You may want to limit the user while they use your framework and correct access control is the way to do it. You can easily guide the users so the users do exactly what you want them to do with your framework.
Document Your Code
This is a must if you want your framework be a professional one. You should be documenting every function and variable the user will use. Documenting and explaining what your code does makes a lot of peoples lives easy. You don't one anyone trying to understand what your code does for half an hour while you could have easily written a small explanation for what the parameters do and one that function or variable should be used for.
Test Your Code
Last but not least do write tests for your code. This does take some time but it assures you that your code works the way it should.
Look at other good frameworks
You should definitely checkout other open source libraries and look at what they have done. Usually there is no point in reinventing the wheel unless you are doing something absolutely different but even then there are very familiar ways to do things. I can suggest you check out the mantle sdk(https://github.com/Mantle/Mantle). Another one is the very popular Alamofire sdk(https://github.com/Alamofire/Alamofire) and also the Realm sdk(https://github.com/realm/realm-cocoa). These are good examples of frameworks. Take a look at them. Look how they have done things. It will give you an insight on how your framework should look like.
I know all of these points may also be valid if you were writing an app but what makes these a must is the fact that you will be sharing your code with others. You may manage by not doing some of these while implementing an app but for a framework things do change a little bit. It is always a pleasure to work with easy to use frameworks which make coding a pleasure. These types of small things will make your framework preferable. Happy coding.
I'm very interested in using GStreamer's iOS framework http://docs.gstreamer.com/display/GstSDK/Installing+for+iOS+development for video streaming, but when I add the framework to a blank project and add a few lines of code to take advantage of its powerful features, the final IPA is 27MB. This is just way to big to be adding to my project, what is the best way to go about stripping this down the the bare necessities as I'm sure I'm only using a small percent of the code that is included in the SDK.
Here's a pic showing the package contents of the IPA:
Thanks!
In the gst_ios_main.h you can disable all the plugins that you don't need (make sure to enable linker optimizations so that unused code is removed). If that's not enough, you can build your own stripped down version of the iOS binaries with http://cgit.freedesktop.org/gstreamer/cerbero/ (you need to remove things from the .package and .recipe files to only build what you need). Just disabling things from gst_ios_main.h should be enough in 99% of the cases though.
Note that by default you'll build applications for multiple architectures, as such the resulting application will be rather large. Depending on your use case you can drop some architectures.
On another note, gstreamer.com is providing an completely outdated version of GStreamer and is in no way related to the GStreamer project. The official website is http://gstreamer.freedesktop.org .
SDKs have their source code encapsulated away from you, the user. You get access only to header files. Thus you just can't extract some class from it because you don't have access to the implementation file.
Of course if this library is opensource you can attempt to isolate one class, but sometimes everything is so deeply connected, that it is close to impossible.
I have read that class-dump utility is used to dump headers from iphone private api's. However, it does work only for objective-c frameworks. I wanted to know how it works for frameworks written in C, example - IOSurface, IOMobileFramebuffer etc.
The second part of the question is very generic. I have an app with me downloaded from cydia or istore. How do i go about reverse engineering the app on a jailbroken deivce (if that is actually needed). To be specifc, I am able to locate the executable binary and the dylibs. I am able to see the frameworks being used. But, how do I make out what functions inside the frameworks are being called by the app ?
Thanks.
I would recommend to break down this question to two questions:
1) "I wanted to know how it works for frameworks written in C, example - IOSurface, IOMobileFramebuffer etc."
I had exactly the same question:
Getting signatures of private API methods for iOS
The answer is
a) Try to google C method to see whether somebody else has disassembled it and found method signature.
b) If nobody did this before, you can be the first who will do it
2) "how do I make out what functions inside the frameworks are being called by the app ?"
There are two types of references to functions in frameworks/libraries:
Compile time references
You use some disassembler, it will list all compile time references to frameworks/dylibs.
Runtime references
These are references when somebody does dlopen, dlsym or NSBundle to use some functions.
You will have to disassemble and look/grep through disassembled code to find where they are used. There will be strings with the names of methods which are used.
I have been given a Shared Object file (.so) and the functions inside of it, but I don't have a clue as to how to use it, or alter it for use in an iOS application. Could someone point me in the right direction?
I know the .so came from an Android application, but I was told I could get it to work in an iOS application as well.
Actually and technically, yes, you can, but not in a way you would ever think.
If it came from Android, it is probably compiled for ARM. So it should be binary-compatible with the ARM CPU in iOS devices. However, iOS doesn't use the usual format of shared objects (that is, the ELF format), but iOS' and OS X's own Mach-O format.
This means that you cannot directly link against this shared object file nor are you able pass it directly to dlopen() and dlsym(). You have to get into serious hacking (something that you probably don't know). This involves loading and relocating the file properly.
An example of this can be found in iOS jailbreak developer and hacker, Comex's GitHub repository Frash, a Flash player for jailbroken iOS devices. Comex essentially wrote an ELF loader module (dubbed "food") for iOS and used it to make Android's libflashplayer.so work on iOS. Pretty neat, huh?
Also note that this is not going to be possible for AppStore apps as it needs dynamic loading and various alterations in the OS.
while technically possible (see h2co3's answer) for anything practical the answer is no
so files arent in the correct binary format
even if they were, dynamic loading is not allowed by appstore