Error when running C++ libraries in iOS Xcode Project

Question

I have C++ files in my iOS Xcode project. Those files uses the next libraries that I'm calling via HomeBrew:

• mpg123/1.26.5
• libgcrypt
• ffmpeg
• libgpg-error
• fftw
• libsndfile

The way I'm including them in the project is by setting the HeaderSearch Paths:

And the Library Search Paths:

That is all I'm doing to call those libraries. The error that I'm getting when I compile the project is the next one:

Undefined symbols for architecture x86_64:
  "_mpg123_scan", referenced from:
      MP3InputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "_mpg123_format_none", referenced from:
      MP3InputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "_mpg123_length", referenced from:
      MP3InputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "_mpg123_close", referenced from:
      MP3InputStream::close() in mp3inputstream.o
      MP3InputStream::detect(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)::ScopedMHandle::~ScopedMHandle() in mp3inputstream.o
  "_fftwf_plan_dft_r2c_1d", referenced from:
      fftar_float(unsigned long, float*, float*) in fft.o
  "_fftwf_free", referenced from:
      free_array_float(float*) in fft.o
  "_mpg123_read", referenced from:
      MP3InputStream::read_frames(std::__1::vector<float, std::__1::allocator<float> >&, unsigned long) in mp3inputstream.o
      MP3InputStream::detect(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "_fftwf_malloc", referenced from:
      new_array_float(unsigned long) in fft.o
  "_sf_readf_int", referenced from:
      SFInputStream::read_frames(std::__1::vector<float, std::__1::allocator<float> >&, unsigned long) in sfinputstream.o
  "_mpg123_open", referenced from:
      MP3InputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
      MP3InputStream::detect(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "_avformat_free_context", referenced from:
      HLSOutputStream::close() in hlsoutputstream.o
  "_mpg123_param", referenced from:
      MP3InputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
      MP3InputStream::detect(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "_avio_open", referenced from:
      HLSOutputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned long, unsigned long, double, unsigned long) in hlsoutputstream.o
  "_mpg123_delete", referenced from:
      MP3InputStream::close() in mp3inputstream.o
      MP3InputStream::detect(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)::ScopedMHandle::~ScopedMHandle() in mp3inputstream.o
  "_avformat_write_header", referenced from:
      HLSOutputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned long, unsigned long, double, unsigned long) in hlsoutputstream.o
  "_avcodec_free_context", referenced from:
      HLSOutputStream::close_stream() in hlsoutputstream.o
  "_swr_free", referenced from:
      HLSOutputStream::close_stream() in hlsoutputstream.o
  "_fftwf_plan_dft_c2r_1d", referenced from:
      fftsr_float(unsigned long, float*, float*) in fft.o
  "_swr_get_delay", referenced from:
      HLSOutputStream::write_audio_frame(Error&) in hlsoutputstream.o
  "_av_log", referenced from:
      HLSOutputStream::write_audio_frame(Error&) in hlsoutputstream.o
  "_mpg123_getformat", referenced from:
      MP3InputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
      MP3InputStream::detect(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "_av_frame_make_writable", referenced from:
      HLSOutputStream::write_audio_frame(Error&) in hlsoutputstream.o
  "_fftwf_execute_dft_r2c", referenced from:
      fftar_float(unsigned long, float*, float*) in fft.o
  "_av_rescale_rnd", referenced from:
      HLSOutputStream::write_audio_frame(Error&) in hlsoutputstream.o
  "_swr_convert", referenced from:
      HLSOutputStream::write_audio_frame(Error&) in hlsoutputstream.o
  "ff_decode(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, WavData&)", referenced from:
      _main in testhls.o
  "_avcodec_send_frame", referenced from:
      HLSOutputStream::write_audio_frame(Error&) in hlsoutputstream.o
  "_gcry_cipher_encrypt", referenced from:
      Random::seed(unsigned long long, Random::Stream) in random.o
      Random::refill_buffer() in random.o
  "_av_strerror", referenced from:
      av_make_error_string(char*, unsigned long, int) in hlsoutputstream.o
  "_avcodec_open2", referenced from:
      HLSOutputStream::open_audio(AVCodec*, AVDictionary*) in hlsoutputstream.o
  "_avio_closep", referenced from:
      HLSOutputStream::close() in hlsoutputstream.o
  "_av_dict_free", referenced from:
      HLSOutputStream::open_audio(AVCodec*, AVDictionary*) in hlsoutputstream.o
  "_swr_alloc", referenced from:
      HLSOutputStream::open_audio(AVCodec*, AVDictionary*) in hlsoutputstream.o
  "_sf_readf_float", referenced from:
      SFInputStream::read_frames(std::__1::vector<float, std::__1::allocator<float> >&, unsigned long) in sfinputstream.o
  "VResampler::VResampler()", referenced from:
      BufferedResamplerImpl<VResampler>::BufferedResamplerImpl(int, int, int) in wmadd.o
      resample(WavData const&, int) in wmget.o
  "_av_opt_set_int", referenced from:
      HLSOutputStream::open_audio(AVCodec*, AVDictionary*) in hlsoutputstream.o
  "_sf_close", referenced from:
      SFOutputStream::open(std::__1::function<SNDFILE_tag* (SF_INFO*)>, int, int, int, SFOutputStream::OutFormat) in sfoutputstream.o
      SFOutputStream::close() in sfoutputstream.o
      SFInputStream::close() in sfinputstream.o
      SFInputStream::open(std::__1::function<SNDFILE_tag* (SF_INFO*)>) in sfinputstream.o
  "_av_opt_set_sample_fmt", referenced from:
      HLSOutputStream::open_audio(AVCodec*, AVDictionary*) in hlsoutputstream.o
  "_mpg123_format", referenced from:
      MP3InputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "_swr_init", referenced from:
      HLSOutputStream::open_audio(AVCodec*, AVDictionary*) in hlsoutputstream.o
  "_av_frame_get_buffer", referenced from:
      HLSOutputStream::alloc_audio_frame(AVSampleFormat, unsigned long long, int, int, Error&) in hlsoutputstream.o
  "_gcry_check_version", referenced from:
      gcrypt_init() in random.o
  "_av_interleaved_write_frame", referenced from:
      HLSOutputStream::write_frame(AVRational const*, AVStream*, AVPacket*) in hlsoutputstream.o
  "_av_packet_rescale_ts", referenced from:
      HLSOutputStream::write_frame(AVRational const*, AVStream*, AVPacket*) in hlsoutputstream.o
  "_av_frame_alloc", referenced from:
      HLSOutputStream::alloc_audio_frame(AVSampleFormat, unsigned long long, int, int, Error&) in hlsoutputstream.o
  "_avcodec_find_encoder", referenced from:
      HLSOutputStream::add_stream(AVCodec**, AVCodecID) in hlsoutputstream.o
  "Resampler::inpsize() const", referenced from:
      BufferedResamplerImpl<Resampler>::write_frames(std::__1::vector<float, std::__1::allocator<float> > const&) in wmadd.o
      void process_resampler<Resampler>(Resampler&, std::__1::vector<float, std::__1::allocator<float> > const&, std::__1::vector<float, std::__1::allocator<float> >&) in wmget.o
  "_av_dict_copy", referenced from:
      HLSOutputStream::open_audio(AVCodec*, AVDictionary*) in hlsoutputstream.o
  "_avcodec_get_name", referenced from:
      HLSOutputStream::add_stream(AVCodec**, AVCodecID) in hlsoutputstream.o
  "_avcodec_alloc_context3", referenced from:
      HLSOutputStream::add_stream(AVCodec**, AVCodecID) in hlsoutputstream.o
  "_av_get_channel_layout", referenced from:
      HLSOutputStream::add_stream(AVCodec**, AVCodecID) in hlsoutputstream.o
  "_av_log_set_level", referenced from:
      HLSOutputStream::HLSOutputStream(int, int, int) in hlsoutputstream.o
  "_mpg123_strerror", referenced from:
      MP3InputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
      MP3InputStream::read_frames(std::__1::vector<float, std::__1::allocator<float> >&, unsigned long) in mp3inputstream.o
  "_gcry_randomize", referenced from:
      Random::gen_key() in random.o
  "_gcry_cipher_close", referenced from:
      Random::~Random() in random.o
  "_gcry_strerror", referenced from:
      Random::die_on_error(char const*, unsigned int) in random.o
  "_gcry_cipher_setctr", referenced from:
      Random::seed(unsigned long long, Random::Stream) in random.o
  "Resampler::setup(unsigned int, unsigned int, unsigned int, unsigned int)", referenced from:
      create_resampler(int, int, int) in wmadd.o
      resample(WavData const&, int) in wmget.o
  "_fftwf_execute_dft_c2r", referenced from:
      fftsr_float(unsigned long, float*, float*) in fft.o
  "_gcry_strsource", referenced from:
      Random::die_on_error(char const*, unsigned int) in random.o
  "_avformat_alloc_output_context2", referenced from:
      HLSOutputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned long, unsigned long, double, unsigned long) in hlsoutputstream.o
  "_gcry_cipher_setkey", referenced from:
      Random::Random(unsigned long long, Random::Stream) in random.o
  "_avcodec_parameters_from_context", referenced from:
      HLSOutputStream::open_audio(AVCodec*, AVDictionary*) in hlsoutputstream.o
  "_sf_open_virtual", referenced from:
      SFOutputStream::open(std::__1::vector<unsigned char, std::__1::allocator<unsigned char> >*, int, int, int, SFOutputStream::OutFormat)::$_1::operator()(SF_INFO*) const in sfoutputstream.o
      SFInputStream::open(std::__1::vector<unsigned char, std::__1::allocator<unsigned char> > const*)::$_1::operator()(SF_INFO*) const in sfinputstream.o
  "_av_rescale_q", referenced from:
      HLSOutputStream::write_audio_frame(Error&) in hlsoutputstream.o
  "_sf_strerror", referenced from:
      SFOutputStream::open(std::__1::function<SNDFILE_tag* (SF_INFO*)>, int, int, int, SFOutputStream::OutFormat) in sfoutputstream.o
      SFOutputStream::write_frames(std::__1::vector<float, std::__1::allocator<float> > const&) in sfoutputstream.o
      SFInputStream::open(std::__1::function<SNDFILE_tag* (SF_INFO*)>) in sfinputstream.o
      SFInputStream::read_frames(std::__1::vector<float, std::__1::allocator<float> >&, unsigned long) in sfinputstream.o
  "_mpg123_outblock", referenced from:
      MP3InputStream::read_frames(std::__1::vector<float, std::__1::allocator<float> >&, unsigned long) in mp3inputstream.o
      MP3InputStream::detect(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "_sf_error", referenced from:
      SFOutputStream::open(std::__1::function<SNDFILE_tag* (SF_INFO*)>, int, int, int, SFOutputStream::OutFormat) in sfoutputstream.o
      SFOutputStream::write_frames(std::__1::vector<float, std::__1::allocator<float> > const&) in sfoutputstream.o
      SFInputStream::open(std::__1::function<SNDFILE_tag* (SF_INFO*)>) in sfinputstream.o
      SFInputStream::read_frames(std::__1::vector<float, std::__1::allocator<float> >&, unsigned long) in sfinputstream.o
  "_gcry_cipher_open", referenced from:
      Random::Random(unsigned long long, Random::Stream) in random.o
  "_mpg123_rates", referenced from:
      MP3InputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "_av_init_packet", referenced from:
      HLSOutputStream::write_audio_frame(Error&) in hlsoutputstream.o
  "VResampler::inpsize() const", referenced from:
      BufferedResamplerImpl<VResampler>::write_frames(std::__1::vector<float, std::__1::allocator<float> > const&) in wmadd.o
      void process_resampler<VResampler>(VResampler&, std::__1::vector<float, std::__1::allocator<float> > const&, std::__1::vector<float, std::__1::allocator<float> >&) in wmget.o
  "_sf_open", referenced from:
      SFOutputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, int, int, int, SFOutputStream::OutFormat)::$_0::operator()(SF_INFO*) const in sfoutputstream.o
      SFInputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)::$_0::operator()(SF_INFO*) const in sfinputstream.o
  "_av_opt_set", referenced from:
      HLSOutputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned long, unsigned long, double, unsigned long) in hlsoutputstream.o
  "Resampler::process()", referenced from:
      BufferedResamplerImpl<Resampler>::write_frames(std::__1::vector<float, std::__1::allocator<float> > const&) in wmadd.o
      void process_resampler<Resampler>(Resampler&, std::__1::vector<float, std::__1::allocator<float> > const&, std::__1::vector<float, std::__1::allocator<float> >&) in wmget.o
  "VResampler::process()", referenced from:
      BufferedResamplerImpl<VResampler>::write_frames(std::__1::vector<float, std::__1::allocator<float> > const&) in wmadd.o
      void process_resampler<VResampler>(VResampler&, std::__1::vector<float, std::__1::allocator<float> > const&, std::__1::vector<float, std::__1::allocator<float> >&) in wmget.o
  "_mpg123_init", referenced from:
      mp3_init() in mp3inputstream.o
  "_av_get_channel_layout_nb_channels", referenced from:
      HLSOutputStream::add_stream(AVCodec**, AVCodecID) in hlsoutputstream.o
  "_gcry_control", referenced from:
      gcrypt_init() in random.o
  "_sf_writef_int", referenced from:
      SFOutputStream::write_frames(std::__1::vector<float, std::__1::allocator<float> > const&) in sfoutputstream.o
  "Resampler::~Resampler()", referenced from:
      BufferedResamplerImpl<Resampler>::~BufferedResamplerImpl() in wmadd.o
      resample(WavData const&, int) in wmget.o
  "_avformat_new_stream", referenced from:
      HLSOutputStream::add_stream(AVCodec**, AVCodecID) in hlsoutputstream.o
  "_av_write_trailer", referenced from:
      HLSOutputStream::close() in hlsoutputstream.o
  "VResampler::~VResampler()", referenced from:
      BufferedResamplerImpl<VResampler>::~BufferedResamplerImpl() in wmadd.o
      resample(WavData const&, int) in wmget.o
  "_av_frame_free", referenced from:
      HLSOutputStream::close_stream() in hlsoutputstream.o
  "_avcodec_receive_packet", referenced from:
      HLSOutputStream::write_audio_frame(Error&) in hlsoutputstream.o
  "Resampler::Resampler()", referenced from:
      BufferedResamplerImpl<Resampler>::BufferedResamplerImpl(int, int, int) in wmadd.o
      resample(WavData const&, int) in wmget.o
  "_mpg123_new", referenced from:
      MP3InputStream::open(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
      MP3InputStream::detect(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in mp3inputstream.o
  "VResampler::setup(double, unsigned int, unsigned int)", referenced from:
      create_resampler(int, int, int) in wmadd.o
      resample(WavData const&, int) in wmget.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

Since you've installed this using brew you are trying to link against libraries built for the Mac. You need to build those libraries for iOS. Note this will typically involve making a fat binary of the different architectures you'll need per library. You can easily test this for fftw and see if the linker errors disappear. Here are some references to build or download a pre-built version.

https://github.com/godock/fftw-build

In theory once you link up against the iOS version, you should see errors like

_fftwf_plan_dft_r2c_1d", referenced from:
      fftar_float(unsigned long, float*, float*) in fft.o
_fftwf_free", referenced from:
      free_array_float(float*) in fft.o

disappear. You can also pick another one of your libraries to replace with the iOS version to test. For example ffmpeg build instructions can be found here.

https://github.com/kewlbear/FFmpeg-iOS-build-script

You'll unfortunately have to hunt down how to build them all.