Overrides throws candidate expects n arguments, n provided

[Banou26]

Using a struct with overrides seems to fail the build, i'm trying to use libtorrent but it throws a few hundred candidate expects x arguments, x provided errors and fails the build

use autocxx::prelude::*;
use std::ffi::CStr;

include_cpp! {
    #include "libtorrent/version.hpp"
    #include "libtorrent/session.hpp"
    
    safety!(unsafe_ffi)

    generate!("libtorrent::version")
    generate!("libtorrent::session")
}

imported code:
https://github.com/arvidn/libtorrent/blob/e9bbf16bdd899f42aef0f0c2b1f214de2c15ac92/include/libtorrent/session.hpp#L160-L190

		explicit session(session_params const& params);
		explicit session(session_params&& params);
		session(session_params const& params, session_flags_t flags);
		session(session_params&& params, session_flags_t flags);
		session();
		session(session_params&& params, io_context& ios);
		session(session_params const& params, io_context& ios);
		session(session_params&& params, io_context& ios, session_flags_t);
		session(session_params const& params, io_context& ios, session_flags_t);
		session(session&&);
		session& operator=(session&&) &;
		session(session const&) = delete;
		session& operator=(session const&) = delete;

ouput:

[...] (a few hundreds/thousands similar warnings)
  cargo:warning=  181 |   session(session_params&& params, io_context& ios, session_flags_t);
  cargo:warning=      |                                                     ^~~~~~~~~~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:180:3: note: candidate: 'libtorrent::session::session(const libtorrent::session_params&, boost::asio::io_context&)'
  cargo:warning=  180 |   session(session_params const& params, io_context& ios);
  cargo:warning=      |   ^~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:180:3: note:   candidate expects 2 arguments, 3 provided
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:179:3: note: candidate: 'libtorrent::session::session(libtorrent::session_params&&, boost::asio::io_context&)'
  cargo:warning=  179 |   session(session_params&& params, io_context& ios);
  cargo:warning=      |   ^~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:179:3: note:   candidate expects 2 arguments, 3 provided
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:164:3: note: candidate: 'libtorrent::session::session()'
  cargo:warning=  164 |   session();
  cargo:warning=      |   ^~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:164:3: note:   candidate expects 0 arguments, 3 provided
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:163:3: note: candidate: 'libtorrent::session::session(libtorrent::session_params&&, libtorrent::session_handle::session_flags_t)'
  cargo:warning=  163 |   session(session_params&& params, session_flags_t flags);
  cargo:warning=      |   ^~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:163:3: note:   candidate expects 2 arguments, 3 provided
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:162:3: note: candidate: 'libtorrent::session::session(const libtorrent::session_params&, libtorrent::session_handle::session_flags_t)'
  cargo:warning=  162 |   session(session_params const& params, session_flags_t flags);
  cargo:warning=      |   ^~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:162:3: note:   candidate expects 2 arguments, 3 provided
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:161:12: note: candidate: 'libtorrent::session::session(libtorrent::session_params&&)'
  cargo:warning=  161 |   explicit session(session_params&& params);
  cargo:warning=      |            ^~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:161:12: note:   candidate expects 1 argument, 3 provided
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:160:12: note: candidate: 'libtorrent::session::session(const libtorrent::session_params&)'
  cargo:warning=  160 |   explicit session(session_params const& params);
  cargo:warning=      |            ^~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:160:12: note:   candidate expects 1 argument, 3 provided
  exit status: 1

[adetaylor]

Thanks. That shouldn't fail in the way you're experiencing.

I wonder if you could kindly follow the instructions here to provide a minimized test case in this bug? At the very least, a repro.json would be very helpful. In my experience 90% of the work is reproducing somebody's situation, and only 10% is actually fixing the bug, so if you can make it easy for me to reproduce it that would be much appreciated.

[Banou26]

I'm really unsure how to reproduce the issue within the minimized tests cases(Being a beginner in both rust and C++ certainely doesn't help me).
Libtorrent is probably doing something weird that's causing issues with autocxx but i couldn't find what it is.

What i could do though if that's fine with you, is make a minimalist docker file that's able to reproduce the issues.
What it would contain is just the basic steps to build libtorrent and a small file with rust's include_cpp and generate! calls that generate the errors.

[adetaylor]

Please just build your project like this: AUTOCXX_REPRO_CASE=repro.json cargo build and then attach repro.json here. That might be enough.

[Banou26]

Oh, sorry for that, i kind of got hung up on the first methods of reporting.
Here's the repro.json

[adetaylor]

Thanks, but that doesn't seem correct. It appears to have some generate_pod! directives which are causing a different problem. I need a repro.json from a build which reproduces the candidate expects x arguments error you have reported.

[Banou26]

I'm not sure what is going wrong, the repro.json i sent is the one that outputs all of the candidate expects x arguments, here's some of the ones i got from building it with the repro

  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:163:3: note:   candidate expects 2 arguments, 3 provided
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:162:3: note: candidate: 'libtorrent::session::session(const libtorrent::session_params&, libtorrent::session_handle::session_flags_t)'
  cargo:warning=  162 |   session(session_params const& params, session_flags_t flags);
  cargo:warning=      |   ^~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:162:3: note:   candidate expects 2 arguments, 3 provided
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:161:12: note: candidate: 'libtorrent::session::session(libtorrent::session_params&&)'
  cargo:warning=  161 |   explicit session(session_params&& params);
  cargo:warning=      |            ^~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:161:12: note:   candidate expects 1 argument, 3 provided
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:160:12: note: candidate: 'libtorrent::session::session(const libtorrent::session_params&)'
  cargo:warning=  160 |   explicit session(session_params const& params);
  cargo:warning=      |            ^~~~~~~
  cargo:warning=/home/dev/fkn-proxy/libtorrent/session.hpp:160:12: note:   candidate expects 1 argument, 3 provided
  exit status: 1

  --- stderr
  /tmp/.tmpg6fyYt:53:9: warning: #pragma once in main file [-Wpragma-once-outside-header]
  #pragma once
          ^
  1 warning generated.


  error occurred: Command "c++" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-g" "-fno-omit-frame-pointer" "-m64" "-I" "/usr/local/include" "-I" "/usr/include" "-I" "/home/dev/fkn-proxy/target/debug/build/rust-http-proxy-libtorrent-87ef3f569c1d3085/out/autocxx-build-dir/include" "-I" "/usr/local/include" "-I" "/usr/include" "-I" "/home/dev/fkn-proxy" "-I" "/home/dev/fkn-proxy/target/debug/build/rust-http-proxy-libtorrent-87ef3f569c1d3085/out" "-Wall" "-Wextra" "-std=c++14" "-o" "/home/dev/fkn-proxy/target/debug/build/rust-http-proxy-libtorrent-87ef3f569c1d3085/out/autocxx-build-dir/cxx/gen0.o" "-c" "/home/dev/fkn-proxy/target/debug/build/rust-http-proxy-libtorrent-87ef3f569c1d3085/out/autocxx-build-dir/cxx/gen0.cxx" with args "c++" did not execute successfully (status code exit status: 1).

and here's my rust code

use autocxx::prelude::*;
include_cpp! {
    #include "libtorrent/session.hpp"
    safety!(unsafe_ffi)
    generate!("libtorrent::session")
}
fn main() {
}

Is there something i could do to give you a better repro.json file?

[adetaylor]

Aha! I have a theory. There was briefly a bug where autocxx made a mistake with the repro.json file. That's probably what happened. In that case I should be able to fix the file and try using it again tomorrow. No need for you to do anything else right now.

[adetaylor]

OK, yes, your repro.json was fine all along, sorry for saying it wasn't right :) I am now working on reducing it to a minimal test case. This is completely automatic but takes a long time - there's quite a lot of code in this repro.json so it will take at least a few days.

[adetaylor]

Here's the results of the minimization. I'm not 100% sure this makes sense, I'll check it out later.

namespace std {
inline namespace a {}
} // namespace std
namespace libtorrent {
char version;
}
namespace std {
namespace a {
template <typename b, typename = b, typename = b> class c;
}
typedef c<char> string;
namespace a {
template <typename, typename, typename> class c { c(); };
} // namespace a
} // namespace std
namespace libtorrent {
struct session;
}
namespace rust {
namespace {
class Str {};
} // namespace
} // namespace rust

[adetaylor]

Annoyingly it seems I must have messed up the minimization. I am starting again. Gah! Another week to wait...

It looks like this library seems to show up multiple bugs in autocxx's codegen, so I anticipate that there may be several cycles here before this works.

[adetaylor]

Sorry for the lack of progress here - this seemed to result in a test case which passed. I think I need to restart the minimization from scratch once again and hope I can reproduce the actual failure that you were encountering.