IOS7 (only) stdlibc++ linking issue

Question

I need help. I had a framwork which was using stdc++ like std:string. Now when i have created new app for IOS7 only there is problem with linking this framework because of problems with stdc++ lib:

Undefined symbols for architecture armv7 "std::basic_string, std::allocator >::_Rep::_S_empty_rep_storage", referenced from ...

I have find out something strange that when i change the Deplyment target to ios6 in this app all is working fine. With ios7 i see errors.

I already have flag set in other linker flags: -lstdc++

Any idea what ami doing wrong?

Atul

are any of the files in your project using the Objective-C++ file extension of ".mm" and if not, what happens when you change one of them to have that file extension? – Ariadne

i use .mm in one of the framework classes which ii link. When i have changed one of the file in normal project nothing has changed and problem is still present. – Atul

what's the c++ dialect set to? – Cofsky

Answer 1

Just an update on this answer:

This step is very important!

Ensure that C++ Standard Library is set to libstdc++ (GNU c++ standard library) in the Apple LLVM 5.0 Compiler Build Settings

Background:

I have an iOS app that abruptly stopped building for iOS 7 with standard library link errors. I had been testing the app successfully on the simulator and on an iPad mini, and archived it as well, but when I added an iPhone 5S for testing, I started getting link errors (possibly because of a new architecture in the mix?).

Searching the link errors on Google, I found advice to explicitly add libstdc++.dylib to the linked libraries. This did not work.

I experimented by adding libstdc++.6.dylib to the linked libraries instead; this eliminated the link errors, but the app crashed in the standard C++ library code very early.

Removing the explicit additions of the library and changing the compiler setting in Build Settings, as noted above, corrected the link errors and runtime problem.

Thanks to rimestad for the pointer!

Lamas

I have done this, but still get the standard library linker errors (I'm trying to link OpenCV). Any idea what else might be going wrong? It happens the same for iOS6 or 7 as deployment target. – Chickabiddy

Yes, clang and gcc have different stdlibs and if you link a library built with gcc you'll end up with this exact issue. – Gemoets

Answer 2

To be honest, I don't like the above answer, as it uses the static lib and not the dynamic!

I have had the problem myself and found that the problem is that xcode is unable to find any C++ files in you project and thus assumes that the libstc++ is not needed!

Quite annoying when you are linking to a static lib that uses it!!

Solution :

• Add a empty .mm file to you project!
• Ensure that C++ Standard Library is set to libstdc++ (GNU c++ standard library) in the Build Settings

This worked for me and I did not have to add -lstdc++ to Other Linker Flags!

Shaia

Thanks @rimestad, that worked! Do you also know why we have to go with libstdc++ instead of libc++? The default is libc++ but it will still not work with libc++. – Consumerism

This should be the accepted answer. Also, you actually don't have to set the C++ Standard Library to libstdc++ anymore after adding an empty cpp or mm file. – Mulry

Add a empty .mm file to you project! rocks – Valerle

@Shaia i had similar linker error(library not found for -lstdc++).i tried everything but no use.any idea? – Grubbs

A complete life saver. Worked for when i was supporting an app for iOS 11. Thanks a lot mate :) – Desiderative

Answer 3

Thanks for your help. I have found solution. I was using -lstdc++ flag in other linker flags but it is not enough now. I had to add "libstdc++.6.0.9.dylib in BuildPhases->Link Binary With Libraries. There was somewhere in the net info that xcode has problems with ios7 stdc++ lib selection and it should be selected manually.

Regards, Marek

Atul

This worked for me (along with adding the empty C++ file). Thanks!! – Liguria

@MarekM, there no libstdc++.6.0.9.dylib in xcode 11+. so what for that ? – Lingerfelt

Answer 4

I had a similar problem, but @MarekM's answer only solve part of my problem, so I tried to add libstdc++.dylib and libstdc++.6.dylib, and that makes all the compiling error gone.

Wynny