LD Failures when building beam as an NDK on Android.

[dexmagic]

Describe the bug
I'm trying to build OTP on Android. At a mimimum I need to build the BEAM vm so compiled Erlang code can be run.
I've got a setup that will successfully compile BEAM, but the linker fails because these symbols are not defined.

To Reproduce
Build BEAM on Android.

Expected behavior
A successful build with just the VM in a library that can be linked into a native Android application.

Affected versions
OTP 26.

Additional context

Here are the errors:
I can't find these symbols in the code, so what should I do about those? Perhaps there's a workaround?

ld: error: undefined symbol: prim_socket_nif_init
  >>> referenced by driver_tab.c
  >>>               CMakeFiles/otp.dir/erts/emulator/x86_64-pc-linux-android/opt/emu/driver_tab.c.o:(erts_static_nif_tab)
  
  ld: error: undefined symbol: erts_pcre_malloc
  >>> referenced by erl_bif_re.c:96 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/beam/erl_bif_re.c:96)
  >>>               CMakeFiles/otp.dir/erts/emulator/beam/erl_bif_re.c.o:(erts_init_bif_re)
  >>> referenced by pcre_compile.c:9437 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/pcre/pcre_compile.c:9437)
  >>>               CMakeFiles/otp.dir/erts/emulator/pcre/pcre_compile.c.o:(erts_pcre_compile2)
  >>> referenced by pcre_compile.c:933 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/pcre/pcre_compile.c:933)
  >>>               CMakeFiles/otp.dir/erts/emulator/pcre/pcre_compile.c.o:(compile_branch)
  >>> referenced 11 more times
  
  ld: error: undefined symbol: erts_pcre_free
  >>> referenced by erl_bif_re.c:97 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/beam/erl_bif_re.c:97)
  >>>               CMakeFiles/otp.dir/erts/emulator/beam/erl_bif_re.c.o:(erts_init_bif_re)
  >>> referenced by erl_bif_re.c:1207 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/beam/erl_bif_re.c:1207)
  >>>               CMakeFiles/otp.dir/erts/emulator/beam/erl_bif_re.c.o:(re_run)
  >>> referenced by erl_bif_re.c:496 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/beam/erl_bif_re.c:496)
  >>>               CMakeFiles/otp.dir/erts/emulator/beam/erl_bif_re.c.o:(build_compile_result)
  >>> referenced 18 more times
  
  ld: error: undefined symbol: erts_pcre_stack_malloc
  >>> referenced by erl_bif_re.c:98 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/beam/erl_bif_re.c:98)
  >>>               CMakeFiles/otp.dir/erts/emulator/beam/erl_bif_re.c.o:(erts_init_bif_re)
  >>> referenced by pcre_exec.c:5271 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/pcre/pcre_exec.c:5271)
  >>>               CMakeFiles/otp.dir/erts/emulator/pcre/pcre_exec.c.o:(match)
  >>> referenced by pcre_exec.c:3677 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/pcre/pcre_exec.c:3677)
  >>>               CMakeFiles/otp.dir/erts/emulator/pcre/pcre_exec.c.o:(match)
  >>> referenced 66 more times
  
  ld: error: undefined symbol: erts_pcre_stack_free
  >>> referenced by erl_bif_re.c:99 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/beam/erl_bif_re.c:99)
  >>>               CMakeFiles/otp.dir/erts/emulator/beam/erl_bif_re.c.o:(erts_init_bif_re)
  >>> referenced by pcre_exec.c:0 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/pcre/pcre_exec.c:0)
  >>>               CMakeFiles/otp.dir/erts/emulator/pcre/pcre_exec.c.o:(erts_pcre_exec)
  >>> referenced by pcre_exec.c:0 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/pcre/pcre_exec.c:0)
  >>>               CMakeFiles/otp.dir/erts/emulator/pcre/pcre_exec.c.o:(erts_pcre_exec)
  >>> referenced 2 more times
  
  ld: error: undefined symbol: erts_pcre_stack_guard
  >>> referenced by erl_bif_re.c:0 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/beam/erl_bif_re.c:0)
  >>>               CMakeFiles/otp.dir/erts/emulator/beam/erl_bif_re.c.o:(erts_init_bif_re)
  >>> referenced by pcre_compile.c:8336 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/pcre/pcre_compile.c:8336)
  >>>               CMakeFiles/otp.dir/erts/emulator/pcre/pcre_compile.c.o:(compile_regex)
  
  ld: error: undefined symbol: esock_atom_name
  >>> referenced by unix_socket_syncio.c:774 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:774)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_info)
  >>> referenced by unix_socket_syncio.c:5108 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:5108)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_ioctl2)
  >>> referenced by prim_net_nif.c:1718 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/common/prim_net_nif.c:1718)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/common/prim_net_nif.c.o:(nif_getifaddrs)
  >>> referenced 1 more times
  
  ld: error: undefined symbol: esock_abort
  >>> referenced by unix_socket_syncio.c:780 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:780)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_info)
  >>> referenced by unix_socket_syncio.c:817 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:817)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:928 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:928)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced 65 more times
  
  ld: error: undefined symbol: esock_open_is_debug
  >>> referenced by unix_socket_syncio.c:802 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:802)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:1037 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:1037)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_plain)
  
  ld: error: undefined symbol: esock_open_use_registry
  >>> referenced by unix_socket_syncio.c:803 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:803)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:1038 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:1038)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_plain)
  
  ld: error: undefined symbol: esock_dbg_printf
  >>> referenced by unix_socket_syncio.c:819 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:819)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:837 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:837)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:847 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:847)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced 332 more times
  
  ld: error: undefined symbol: esock_getopt_int
  >>> referenced by unix_socket_syncio.c:953 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:953)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:982 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:982)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:953 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:953)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced 2 more times
  
  ld: error: undefined symbol: esock_open_which_protocol
  >>> referenced by unix_socket_syncio.c:855 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:855)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:855 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:855)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:1098 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:1098)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_plain)
  
  ld: error: undefined symbol: esock_atom_domain
  >>> referenced by unix_socket_syncio.c:968 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:968)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  
  ld: error: undefined symbol: esock_decode_domain
  >>> referenced by unix_socket_syncio.c:972 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:972)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  
  ld: error: undefined symbol: esock_atom_type
  >>> referenced by unix_socket_syncio.c:997 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:997)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:5642 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:5642)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(decode_cmsghdrs)
  >>> referenced by unix_socket_syncio.c:6060 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:6060)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_recvmsg)
  >>> referenced 1 more times
  
  ld: error: undefined symbol: esock_decode_type
  >>> referenced by unix_socket_syncio.c:1000 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:1000)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  
  ld: error: undefined symbol: esock_make_invalid
  >>> referenced by unix_socket_syncio.c:0 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:0)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:0 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:0)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_sendmsg)
  >>> referenced by unix_socket_syncio.c:0 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:0)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_sendmsg)
  >>> referenced 2 more times
  
  ld: error: undefined symbol: esock_atom_protocol
  >>> referenced by unix_socket_syncio.c:1014 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:1014)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:1014 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:1014)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by prim_net_nif.c:4502 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/common/prim_net_nif.c:4502)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/common/prim_net_nif.c.o:(nif_getaddrinfo)
  
  ld: error: undefined symbol: esock_extract_int_from_map
  >>> referenced by unix_socket_syncio.c:1013 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:1013)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  >>> referenced by unix_socket_syncio.c:1013 (/Users/richard/Development/git-dexopruntime/erlang-android/otp-android/app/src/main/cpp/erts/emulator/nifs/unix/unix_socket_syncio.c:1013)
  >>>               CMakeFiles/otp.dir/erts/emulator/nifs/unix/unix_socket_syncio.c.o:(essio_open_with_fd)
  

[garazdawi]

The Android support has been contributed by external contributors, so this is not something that we can help with. I'm putting the label "help wanted" on it to see if anyone else can help you out.

[dexmagic]

O.K. Thank you.
I just now got AtomVM to build in Android Studio from source. So that's great!
But I would still like help to understand why those symbols are missing from the linker and what the workaround might be.

Cheers.

[JeromeDeBretagne]

Could you describe the steps you are using to cross-compile Erlang / OTP and your setup (NDK versions, etc.)?

I've been able to build OTP 26 for Android successfully following the Android-specific documentation from https://github.com/erlang/otp/blob/master/HOWTO/INSTALL-ANDROID.md