I currently have a single Xcode project for a very large code base, I'll call it Project X, which I am dividing into a bunch of sub projects ( Projects A, B, C ).
So far, each of these projects compiles, on their own, just fine. They all produce static libraries. Project B and Project C are dependent on the static library produced by Project A in order to build.
I have another xcode project, Project Z, that requires the static libraries produced by Projects B and C. Herein lies the problem. When Project Z enters the linker phase, things blow up - duplicate symbols are found within the libs for Projects B and C for the code they originally linked against in Project A!
I'm pretty new to the world of static libraries, and I'm unsure of how to move forward with Project Z, or how to modify the other projects so that they are linking against the same Project A lib. I have a feeling it's not possible. What are my options here?
Edit:
I should clarify that Project B and Project C need to build into separate static libs because some clients will only require one or the other.
Also, I'm having this dilemma on both OSX and iOS platforms.
I realize that I could solve this problem on OSX by building the projects as dynamic libraries. However, I'd prefer not to do this, and it still leaves me with same issue on iOS.
Static libraries should never include other static libraries (or third party code in general). A static library is just a bundle of .o files glued together. So if you have multiple copies of the same information, it's going to blow up.
Each static library should just have its own code in it. The final application is responsible for linking all the required libraries together (including libraries required by libraries). This way there is exactly one copy of each thing linked.
This sounds like exactly the sort of problem CoacoaPods was created to solve. If you define pods for each of theses projects then Z should be able to determine and link against all of its dependencies all the way up the chain without introducing duplicate symbols.
Related
Does anyone have a guide to setting up a project that produces a static library under recent versions of Xcode? There are a few for older versions, but they use a project setting called "C/C++ Library" which seems to have been removed.
I notice "External build system" is still in there, and maybe that's a solution? The C code won't be changing structure too much, so a makefile could be a solution - but I've never used this type before, so I'd like to hear from people that have.
Ultimately the C code will be consumed by a Swift/Cocoa application. Am I correct in thinking that I simply include both projects in a workspace, drag the .a and bridging .h into the Swift project, and go?
I'm trying to write a simple game engine for iOS in Objective C and C++ using Xcode.
I've made a game project and a game engine project. The latter is added to the former as a subproject. The engine is also added as a target dependency and as a binary to be linked in the game project.
My engine uses CADisplayLink so I add QuartzCore.framework in the engine project's "Link binary with libraries list" (found in Build phases).
Now, when I try to build my game project (the project with the subproject), I get this error:
Undefined symbols for architecture i386: "_OBJC_CLASS_$_CADisplayLink", referenced from: objc-class-ref in libVoya-iOS.a
This error only happens when building from the game project - doing it from the engine project works fine. If I add QuartzCore.framework to the game project building works fine.
Can it really be true I have to specifically require frameworks that one of my target dependencies already have required? In this case: My engine (sub project) already links QuartzCore - is it really necessary to also do this in the projects using this engine? It feels like double work for no reason.
Or perhaps I've just completely misunderstood something? :)
Add QuartzCore framework to fix this issue.
I've now found the answer to my question and I'd like to share it.
Static libraries are nothing more than a grouping of the compiled versions of the library's source files. They do not include any libraries they themselves might depend on.
Fusing all dependencies together happens only when you build the actual executable in the very end. For this reason, your application should indeed link against your dependencies' dependencies.
As for the example in my question, that means that my game should link QuartzCore while my game engine should not (even though it is my GameEngine who is using it).
Learn more here:
Duplicate symbol: Include static lib A in static lib B, also include lib A and B in XCode Project
Linking static libraries, that share another static library
I believe this is because you're using a target dependency instead of linking against a precompiled library.
How to build a .bundle from source code?
This might sound like a simple problem but it has been hurdling me for a week...
Here is my problem:
I have a bunch of .c and .h files that are organized in a folder and its sub folders. The source code was written and compiled with gcc make and tested by many other make tools. The source code has some utilities and command line tools and it has more code that serve as library for those utilities and tools. It is the files that serve as libraries that I want to reuse. (By library I don't mean static library or something, I just mean that some .c and .h files in certain subfolders provide functions that can be called by some other .c files. I want to be able to call those functions, too)
Yet my problem is more complex than that: I need to build those .c and .h into a bundle to reuse it. I am not writing my application in C; I am developing in Unity and Unity can only take in .bundle files on Mac OS.
Here is my goal:
Organize the source code folder in a proper way so that I can build them into a bundle in Xcode 4.
Here is where I got stuck:
When building the project I got the following error:
Duplicate symbol _main in
/Users/zeningqu/Library/Developer/Xcode/DerivedData/ccn-cfygrtkrshubpofnfxalwimtyniq/Build/Intermediates/ccn.build/Debug/ccn.build/Objects-normal/i386/ccndsmoketest.o
and
/Users/zeningqu/Library/Developer/Xcode/DerivedData/ccn-cfygrtkrshubpofnfxalwimtyniq/Build/Intermediates/ccn.build/Debug/ccn.build/Objects-normal/i386/ccnd_main.o
for architecture i386
I can relate to this error because I can find lots of main entries in the source code. Most of them are test utilities.
Here is what I tried:
I tried removing all those utility .c files but with no luck. The error is still there. I delete and delete until some files cannot find the definition of the function they are calling. So I had to stop there.
Though I wasn't able to build a bundle I was able to build a C/C++ static library (with an .a extension). After I got the .a file I tried to put it into another Xcode project and tried to build it into a bundle. I could build a bundle in that way, but then I had problem accessing the content of the bundle. How do I call functions defined in a .a static library if that library is hidden in a bundle? I read about Apple's documentation which says:
Note: Some Xcode targets (such as shell tools and static libraries) do
not result in the creation of a bundle or package. This is normal and
there is no need to create bundles specifically for these target
types. The resulting binaries generated for those targets are intended
to be used as is.
(quoted from: https://developer.apple.com/library/mac/#documentation/CoreFoundation/Conceptual/CFBundles/AboutBundles/AboutBundles.html#//apple_ref/doc/uid/10000123i-CH100-SW1)
Here is what I thought about:
I thought about replacing all main with something like main_sth. But the source code was not written by me so I didn't want to modify it. (It just doesn't feel like a proper way of doing things to me...)
I learnt that Xcode has gcc compiler built in. So I guess if gcc can make it, so can Xcode? It's just a wild guess - I am not familiar with Xcode and gcc.
Here is a summary of my questions:
Is there a way to properly organize a pile of code previously compiled and made by gcc make so that they can be built into an Xcode bundle?
Is it meaningful to put a .a library in an Xcode project and build it into a bundle? If it is meaningful, how do I call functions defined in .a after it is built into a bundle?
Is it proper to just replace all main() entries with something else?
Alright I think I have figured out at least one solution to the problem.
The duplicate main error was caused by a bunch of main entries in my source code. When the code was compiled by gcc make, I guess the author defined a sort of compilation order so that duplicate mains won't be an issue. (If you know how to do this, please let me know. I barely know make tools.) But when I just add the entire source code folder into my Xcode project, of course Xcode would complain during linking...
As I was unwilling to modify the source code (because the source code library is not developed by me), I decided to use another strategy to walk around this problem.
If your duplicate main error was reported from your own code, you can stop reading here. But if you are like me, with a bunch of gcc compiled source code and badly need a bundle yet don't know what to do, I may be able to help.
Okay here is what I did:
I set up an empty workspace.
I built a C/C++ static library project.
Import my entire source code folder into the static library project.
Set some header search path for the static library project.
Build the static library project. (Now I have a .a library which I could link against)
I set up another project, with a bundle target.
At the bundle project -> Build Phases -> Link Binary with Libraries, add the .a library that I just built.
At the bundle project -> edit scheme -> Build, add the static library project to the scheme and move it up the list so that it is built prior to my bundle project.
Then add .h files of my library project to my bundle project as references.
After that, add a .c file in my bundle project that basically functions as a wrapper. I picked a function that I want to call in Unity, wrote a wrapper function in the new .c file, and was able to build the bundle.
After several trial and error, I was able to import the bundle into Unity and was able to call the test function from Unity.
I was really excited about this! Though it's not completed yet I think this gives me hope and I am confident I can use the source code now! And the best thing about this solution is that I don't have to modify the library code developed by others. Whenever they update their code, I just update my .a library and that's it!
Though I have listed 11 steps I still feel that there are lots of details that I missed. So here are my references:
I followed this tutorial to build my source code into a static library: http://www.ccnx.org/?post_type=incsub_wiki&p=1315
I followed this blog to link static library against my bundle code and twist build phases and search headers: http://blog.carbonfive.com/2011/04/04/using-open-source-static-libraries-in-xcode-4/
I followed this doc to import my bundle to Unity3D Pro as a plugin: http://unity3d.com/support/documentation/Manual/Plugins.html
I strongly recommend the second reference because that's what solved my problem!
Though the problem is almost solved there are still a few things that I haven't figured out:
I don't know if a wrapper function is at all necessary. I will try this out tomorrow and come back to update.
-- I am coming back to update: the wrapper function is NOT necessary. Just make sure you have all the headers in your bundle project and you will be able to use all the data structures and call functions defined in your headers.
I haven't used NSBundle class though I read a few docs about it. Previously I was thinking about using that class to access my .a library encapsulated in my bundle, but as I found the solution I wrote above, I didn't try the class out.
Lastly, if you have better solution, please don't hesitate to let me know!
I tried to follow the steps in the accepted answer, but had no luck. In the end, I realised step 10 needed to be modified slightly:
Create a dummy.c under (.bundle) project and the dummy.c can just be totally empty.
Remove the setting for the library you want to link inside Link Binary With Libraries
Instead use -Wl,-force_load,$(CONFIGURATION_BUILD_DIR)/libYourLib.a or -all_load to Other Linker Flags
PS: And also can use sub-project instead of workspace. and use Target Dependencies instead of Edit Scheme to achieve the same effect.
I have a need to create a static library which will some of it's own code and it will also contain a number of other static libraries I have written.
So normally I have a main project A.xcodeproj which depends on B.xcodeproj which in turn depends on C, D, E etc.
My company has a requirement to distribute only a static library with a simple app, and for there to only be one library sent out, not a multitude of libC.a libD.a etc.
So I create A_static.xcodeproj which has simple application API calls and links to libB.a but everytime I try this libB.a only contains the symbols for B.xcodeproj, I can not get to it also contain libC.a libD.a etc.
Is there an easy way to do this in XCode that I'm missing?
Thanks
It sounds very much like you need to use frameworks. Allows you to bundle multiple libraries and files together into 1 bundle that other parties can include. I'm in the same boat where I work. I've used this guide on github to get our frameworks up and running. Worked great for me.
iOS Framework
I'm building a project which consists of two .net executables, and a class library with common components that the two executables share. For ease of distribution, I was hoping to be able to distribute the two executables without distributing the dll (grab & run distribution).
Is there any way to have visual studio compile the contents of the dll into each executable without manually copying the classes into each project (and thereby replicating the code in more than one place)?
Don't make it a DLL. Make it a static library instead.
Digging around on SO I found a duplicate question which stated the problem quite a bit more clearly than I did.
ILMerge seems to be the solution.
Static Linking of libraries created on C# .NET