ambiguous constructor error with clang7 from ndk

[DDoSolitary]

I'm trying to build boost 1.80 with the Clang 7 compiler provided by NDK r18b and got the following error

In file included from libs/thread/src/future.cpp:10:
In file included from ./boost/thread/futures/future_error_code.hpp:13:
In file included from ./boost/system/error_code.hpp:13:
./boost/system/detail/error_code.hpp:615:29: error: call to constructor of 'std::error_code' is ambiguous
            std::error_code e2( *this );
                            ^   ~~~~~
/opt/android-toolchain/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../include/c++/4.9.x/system_error:500:24: note: candidate is the implicit copy constructor
class _LIBCPP_TYPE_VIS error_code
                       ^
/opt/android-toolchain/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../include/c++/4.9.x/system_error:500:24: note: candidate is the implicit move constructor
1 error generated.

It seems to be the same error for which a special deleted declaration was added a6c4b63. But the check fails to catch my clang version.

$ /opt/android-toolchain/bin/aarch64-linux-android-clang++ --version
Android (4751641 based on r328903) clang version 7.0.2 (https://android.googlesource.com/toolchain/clang 003100370607242ddd5815e4a043907ea9004281) (https://android.googlesource.com/toolchain/llvm 1d739ffb0366421d383e04ff80ec2ee591315116) (based on LLVM 7.0.2svn)
Target: aarch64-none-linux-android21
Thread model: posix
InstalledDir: /opt/android-toolchain/bin

[pdimov]

It looks like the same issue, yes. Does it work if you define the macro BOOST_SYSTEM_CLANG_6, which is defined for Clang 6 and earlier by

system/include/boost/system/detail/config.hpp

Line 68 in 36e1236

# define BOOST_SYSTEM_CLANG_6

?

[DDoSolitary]

@pdimov Yes, manually defining the macro fixes the error.

[pdimov]

The normal Clang 7.0.0, 7.0.1 works, so this Android build should be something slightly different that identifies as 7.0.2 but isn't. Any suggestions as to how the condition in detail/config.hpp needs to be changed to fix your issue?

#if defined(__clang__) && (__clang_major__ < 7 || (defined(__APPLE__) && __clang_major__ < 11) || (defined(__ANDROID__) && __clang_major__ == 7))

perhaps?

[DDoSolitary]

I also tested normal clang 7.0.0 and can confirm it works. I think adding the __ANDROID__ && clang == 7 check should fix the error for me, though I didn't test any newer clang versions provided by Android NDK

[pdimov]

OK, let's give it a try.