undefined reference to `libiconv'

[senisioi]

Bug description

I have been trying to compile marianMT on a docker container with this nvcr image nvcr.io/nvidia/pytorch:21.12-py3
and it seems the 3rd party pathie library is making all marian executables fail to link because of the following error:

/usr/bin/ld: ../libmarian.a(pathie.cpp.o): in function `Pathie::convert_encodings(char const*, char const*, std::__cxx11::basic_string<char,
 std::char_traits<char>, std::allocator<char> > const&)':
/marian/src/3rd_party/pathie-cpp/src/pathie.cpp:121: undefined reference to `libiconv_open'
/usr/bin/ld: /marian/src/3rd_party/pathie-cpp/src/pathie.cpp:152: undefined reference to `libiconv'
/usr/bin/ld: /marian/src/3rd_party/pathie-cpp/src/pathie.cpp:161: undefined reference to `libiconv_close'

How to reproduce

Pull the nvcr image nvcr.io/nvidia/pytorch:21.12-py3 and install all dependencies.

git clone --depth 1 --branch 1.11.0 https://github.com/marian-nmt/marian /marian
mkdir -p build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release -DUSE_SENTENCEPIECE=ON -DUSE_MPI=ON -DCOMPILE_CPU=on -DCOMPILE_SERVER=on  && make -j8 

Context

• Marian version: 1.11.0
• CMake command: Type the cmake command you used and attach the output of --build-info all
• Log file: Attach your training/decoding logs

The dependency install for docker is based strongly on this repo

[senisioi]

I found a fix by commenting the if statement at this line to always

set(EXT_LIBS ${EXT_LIBS} iconv)

Is that condition really necessary only for APPLE?

A working example is available in my branch

Update: it seems this only works if I compile libiconv in the image. Now the comment at line 168 makes perfect sense.