Compile error with clang on armbian aarch64

[iamleeg]

Environment

clang 3.8.1, cmake 3.15.4, on Armbian (Debian 9.13)

Steps to reproduce

export CC=clang
export CXX=clang++
cmake ..
make -j4

Error message

[  7%] Building CXX object CMakeFiles/objc.dir/objcxx_eh.cc.o
/home/leeg/Projects/libobjc2/objcxx_eh.cc:19:18: error: exception specification
      in declaration does not match previous declaration
extern "C" void *__cxa_allocate_exception(size_t) noexcept;
                 ^
/home/leeg/Projects/libobjc2/objcxx_eh.h:18:7: note: previous declaration is
      here
void *__cxa_allocate_exception(size_t thrown_size) CXA_ALLOCATE_EXCEPTIO...
      ^
1 error generated.

What I tried

Installing llvm libc++, and using ccmake to -DCXX_RUNTIME_LIB=/usr/lib/aarch64-linux-gnu/libc++.so yielded this error:

 CMake Error at CMakeLists.txt:321 (separate_arguments):
   separate_arguments given unknown argument NATIVE_COMMAND

So I then just tried passing that constructed argument to cmake. That worked, but I get the same error.

Notes

In fairness the comment right above this line says that clang would throw a type mismatch error, I would switch to gcc except the cmake configure phase strongly advises against that:

WARNING: It is strongly recommended that you compile with clang

[davidchisnall]

Thanks for the report.

I'm not sure why I added that line, but can you try deleting line 19 of objcxxeh.cc? It appears to be duplicating a declaration from the header, incorrectly. If that works, please raise a PR that does it.

Note: clang 3.8.1 is ancient (2016). I doubt that it will work, it definitely won't support the v2 ABI. I'd strongly recommend that you use clang 9 (2019) or later.

[iamleeg]

Thanks for your help @davidchisnall, I confirm that fixes the immediate issue and clang 3.8.1 fails because it doesn't understand class properties. I'm using that version because it's "whatever's in Debian", but I'll make the PR then upgrade the compiler and move on.