在 iOS Xcode 项目中运行 C++ 库时出错

如何解决在 iOS Xcode 项目中运行 C++ 库时出错

我的 iOS Xcode 项目中有 C++ 文件。这些文件使用我通过 HomeBrew 调用的下一个库：

• mpg123/1.26.5
• libgcrypt
• ffmpeg
• libgpg 错误
• fftw
• libsndfile

我将它们包含在项目中的方式是设置 HeaderSearch Paths：

和图书馆搜索路径：

这就是我调用这些库所做的全部工作。我编译项目时遇到的错误是下一个：

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",std::__1::allocator<char> > const&) in mp3inputstream.o
  "_mpg123_length",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::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::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,unsigned long) in sfinputstream.o
  "_mpg123_open",std::__1::allocator<char> > const&) in mp3inputstream.o
      MP3InputStream::detect(std::__1::basic_string<char,std::__1::allocator<char> > const&) in mp3inputstream.o
  "_avformat_free_context",referenced from:
      HLSOutputStream::close() in hlsoutputstream.o
  "_mpg123_param",std::__1::allocator<char> > const&) in mp3inputstream.o
  "_avio_open",referenced from:
      HLSOutputStream::open(std::__1::basic_string<char,std::__1::allocator<char> > const&,unsigned long,double,unsigned long) in hlsoutputstream.o
  "_mpg123_delete",std::__1::allocator<char> > const&)::ScopedMHandle::~ScopedMHandle() in mp3inputstream.o
  "_avformat_write_header",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*) 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",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",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,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*,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",AVDictionary*) in hlsoutputstream.o
  "_swr_alloc",AVDictionary*) in hlsoutputstream.o
  "_sf_readf_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",AVDictionary*) in hlsoutputstream.o
  "_sf_close",referenced from:
      SFOutputStream::open(std::__1::function<SNDFILE_tag* (SF_INFO*)>,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",AVDictionary*) in hlsoutputstream.o
  "_mpg123_format",std::__1::allocator<char> > const&) in mp3inputstream.o
  "_swr_init",AVDictionary*) in hlsoutputstream.o
  "_av_frame_get_buffer",referenced from:
      HLSOutputStream::alloc_audio_frame(AVSampleFormat,unsigned long long,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",AVPacket*) in hlsoutputstream.o
  "_av_frame_alloc",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::allocator<float> >&) in wmget.o
  "_av_dict_copy",AVDictionary*) in hlsoutputstream.o
  "_avcodec_get_name",AVCodecID) in hlsoutputstream.o
  "_avcodec_alloc_context3",AVCodecID) in hlsoutputstream.o
  "_av_get_channel_layout",AVCodecID) in hlsoutputstream.o
  "_av_log_set_level",referenced from:
      HLSOutputStream::HLSOutputStream(int,int) in hlsoutputstream.o
  "_mpg123_strerror",std::__1::allocator<char> > const&) in mp3inputstream.o
      MP3InputStream::read_frames(std::__1::vector<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",Random::Stream) in random.o
  "Resampler::setup(unsigned int,unsigned int,unsigned int)",referenced from:
      create_resampler(int,int) in wmget.o
  "_fftwf_execute_dft_c2r",float*) in fft.o
  "_gcry_strsource",unsigned int) in random.o
  "_avformat_alloc_output_context2",unsigned long) in hlsoutputstream.o
  "_gcry_cipher_setkey",referenced from:
      Random::Random(unsigned long long,Random::Stream) in random.o
  "_avcodec_parameters_from_context",AVDictionary*) in hlsoutputstream.o
  "_sf_open_virtual",referenced from:
      SFOutputStream::open(std::__1::vector<unsigned char,std::__1::allocator<unsigned char> >*,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",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,unsigned long) in sfinputstream.o
  "_mpg123_outblock",std::__1::allocator<char> > const&) in mp3inputstream.o
  "_sf_error",unsigned long) in sfinputstream.o
  "_gcry_cipher_open",Random::Stream) in random.o
  "_mpg123_rates",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::allocator<float> >&) in wmget.o
  "_sf_open",referenced from:
      SFOutputStream::open(std::__1::basic_string<char,SFOutputStream::OutFormat)::$_0::operator()(SF_INFO*) const in sfoutputstream.o
      SFInputStream::open(std::__1::basic_string<char,std::__1::allocator<char> > const&)::$_0::operator()(SF_INFO*) const in sfinputstream.o
  "_av_opt_set",unsigned long) in hlsoutputstream.o
  "Resampler::process()",std::__1::allocator<float> >&) in wmget.o
  "VResampler::process()",std::__1::allocator<float> >&) in wmget.o
  "_mpg123_init",referenced from:
      mp3_init() in mp3inputstream.o
  "_av_get_channel_layout_nb_channels",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",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) in wmget.o
  "_mpg123_new",std::__1::allocator<char> > const&) in mp3inputstream.o
  "VResampler::setup(double,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)

解决方法

由于您使用 brew 安装了它，因此您正在尝试链接为 Mac 构建的库。您需要为 iOS 构建这些库。请注意，这通常涉及为每个库所需的不同架构制作一个胖二进制文件。您可以轻松测试 fftw 并查看链接器错误是否消失。以下是构建或下载预构建版本的一些参考资料。

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

理论上，一旦您连接到 iOS 版本，您应该会看到类似

的错误

_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

消失。您还可以选择另一个库来替换 iOS 版本进行测试。例如，可以在此处找到 ffmpeg 构建说明。

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

不幸的是，您将不得不寻找如何构建它们。