spinlock_gcc_arm.hpp fails when building iOS arm64

[Joe Radjavitch <joerad11@…>]

I am using boost in my iOS and Android applications and building for arm64 in iOS fails in spinlock_gcc_arm because the the SWP instruction and LDREX are not part of the arm64 instruction set. I do not have enough knowledge about the ARM assembly instructions to implement a proper fix for this myself and was hopeful someone with more expertise could provide a fix for the next release (or a patch for the current, if possible).

[Peter Dimov]

What compiler are you using?

[anonymous]

Hello...I am trying to build using Xcode 5, which uses LLVM 5.0. Thanks.

[Peter Dimov]

Does it support std::atomic?

[anonymous]

Yes, I believe it does.

[Peter Dimov]

I've added the ability to direct shared_ptr to use an std::atomic implementation by using #define BOOST_SP_USE_STD_ATOMIC. You can find the commit at ​https://github.com/boostorg/smart_ptr/commit/fed15ad8c50921cbfc0365156e4e4f4454dc1b91. Eventually, this implementation will be selected by default when std::atomic is autodetected to be present and functional, but for now, you can apply this patch, define the macro and see if that helps.

[anonymous]

Running clang Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn) like this:

clang++ -fvisibility=hidden" "-fvisibility-inlines-hidden" "-DBOOST_SP_USE_STD_ATOMIC" "-std=c++11" "-stdlib=libc++"

I get the following error:

In file included from ./boost/shared_ptr.hpp:17:
In file included from ./boost/smart_ptr/shared_ptr.hpp:34:
./boost/smart_ptr/detail/spinlock_pool.hpp:80:89: error: call to deleted constructor of 'std::atomic_flag' (aka 'std::__1::atomic_flag')
    BOOST_DETAIL_SPINLOCK_INIT, BOOST_DETAIL_SPINLOCK_INIT, BOOST_DETAIL_SPINLOCK_INIT, BOOST_DETAIL_SPINLOCK_INIT, BOOST_DETAIL_SPINLOCK_INIT, 
                                                                                        ^~~~~~~~~~~~~~~~~~~~~~~~~~
./boost/smart_ptr/detail/spinlock_std_atomic.hpp:81:38: note: expanded from macro 'BOOST_DETAIL_SPINLOCK_INIT'
#define BOOST_DETAIL_SPINLOCK_INIT { ATOMIC_FLAG_INIT }
                                     ^~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/atomic:1510:26: note: expanded from macro 'ATOMIC_FLAG_INIT'
#define ATOMIC_FLAG_INIT {false}
                         ^~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/atomic:1384:5: note: function has been explicitly marked deleted here
    atomic_flag(const atomic_flag&) = delete;
    ^

[Peter Dimov]

I get the same with clang 3.4 for Windows; looks like a clang bug, as MSVC and g++ have no problems with this code.

[Peter Dimov]

​http://llvm.org/bugs/show_bug.cgi?id=18992

[Peter Dimov]

What is the actual .cpp file that fails with the above error?

[Peter Dimov]

This patch:

​https://github.com/boostorg/smart_ptr/commit/fbb851097fa800fa9f19d6936906af7777d90215

should take care of the issue.