Question 130325 in Xcode Question posted in
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Xcode – Compilation issue on mac Error: No matching constructor for initialization of 'wavenet::WaveNet'

I have a Compilation issue on mac, I’m trying to build this Neural Amp Modeler https://github.com/sdatkinson/iPlug2/tree/main/Examples/NAM on a Apple M1 MBP macOS 12.6 / Xcode 14.0

The code in that repository works on Windows but on my machine I get these errors:

Error: No matching constructor for initialization of 'wavenet::WaveNet'

In instantiation of function template specialization:

    'std::make_unique<wavenet::WaveNet, std::vector<wavenet::LayerArrayParams> &, 
const float &, const bool &, nlohmann::basic_json<>, std::vector<float> &>'

In file included from /Users/username/Dev/iPlug2/Examples/NAM/get_dsp.cpp

note: wavenet.h note: candidate constructor not viable: expects an lvalue for 4th argument
note: candidate constructor (the implicit copy constructor) not viable: requires 1 argument, but 5 were provided
note: candidate constructor (the implicit move constructor) not viable: requires 1 argument, but 5 were provided'

I don’t understand why it works on windows, I can post more code if need it and all the files are on the repository, Thanks!

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2

Answers


  1. 0

    I made a quick guess based on my experiences (Unfortunately, I cannot test it on a Mac).

    Since the compile error comes from get_dsp.cpp we should try to fix it there before trying to change something in the class WaveNet itself.

    The make_unique call is issued in get_dsp.cpp, line 83.

    In line 87 is the 4th parameter to the constructor:

    architecture == "CatWaveNet" ? config["parametric"] : nlohmann::json{}

    I guess the default constructed nlohmann::json after the : is the root source of the compile error. This creates an un-named temporary object which is an rvalue.
    But the constructor requires an lvalue (non-const reference to a nlohmann::json).
    To fix that we must ensure we pass something which can act as an lvalue, so we need a named object, like this:

    auto my_json = architecture == "CatWaveNet" ? config["parametric"] : nlohmann::json{};

    This must be placed before the return statement in line 82 and then use "my_json" as constructor parameter in line 87.
    The complete changed block will then look like this:

    auto my_json = architecture == "CatWaveNet" ? config["parametric"] : nlohmann::json{};
return std::make_unique<wavenet::WaveNet>(
  layer_array_params,
  head_scale,
  with_head,
  my_json,
  params
);

    Does it solve the problem?

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  2. 0

    So, just out of curiosity I did eventually get the MacBook to start compiling and reproduce your error. I’m not very familiar with MacOS at all, it is the system chosen by my new employer.

    There is additional stuff in need of some TLC: python 2.7 is deprecated, and I’m sure you discovered as well that std::exception("message") is another non-standard implementation provided by Microsoft.

    However, I can now safely say that this really was the last non-portable code in this particular project, and that the nlohman::json parameter can be made a reference to const with one more change. To get rid of the last error you mentioned, modify line 328

      for (nlohmann::json::iterator it = parametric.begin(); it != parametric.end(); ++it)

    to

      for (auto it = parametric.begin(); it != parametric.end(); ++it)
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