Warnings with gcc's -Weffc++

[svenihoney]

If I compile my sources with gcc and with -Weffc++ I get the following warnings:

[1/3] Building CXX object CMakeFiles/trompeloeil-effcpp-test.dir/test.cpp.o
In file included from /home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil.hpp:29,
                 from /home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/trompeloeil.hpp:22,
                 from /home/sven/projects/trompeloeil-effcpp/test.cpp:2:
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/mock.hpp: In constructor 'trompeloeil::trace_agent::trace_agent(trompeloeil::location, const char*, trompeloeil::tracer*)':
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/mock.hpp:2129:5: warning: 'trompeloeil::trace_agent::os' should be initialized in the member initialization list [-Weffc++]
 2129 |     trace_agent(
      |     ^~~~~~~~~~~
In file included from /home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil.hpp:30:
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/lifetime.hpp: At global scope:
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/lifetime.hpp:62:8: warning: 'struct trompeloeil::lifetime_monitor' has pointer data members [-Weffc++]
   62 | struct lifetime_monitor : public expectation
      |        ^~~~~~~~~~~~~~~~
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/lifetime.hpp:62:8: warning:   but does not declare 'operator=(const trompeloeil::lifetime_monitor&)' [-Weffc++]
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/lifetime.hpp:136:22: note: pointer member 'trompeloeil::lifetime_monitor::call_name' declared here
  136 |   char const        *call_name;
      |                      ^~~~~~~~~
In file included from /home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil.hpp:37:
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/sequence.hpp:83:9: warning: 'class trompeloeil::sequence_matcher' has pointer data members [-Weffc++]
   83 |   class sequence_matcher : public list_elem<sequence_matcher>
      |         ^~~~~~~~~~~~~~~~
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/sequence.hpp:83:9: warning:   but does not declare 'trompeloeil::sequence_matcher(const trompeloeil::sequence_matcher&)' [-Weffc++]
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/sequence.hpp:83:9: warning:   or 'operator=(const trompeloeil::sequence_matcher&)' [-Weffc++]
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/sequence.hpp:162:17: note: pointer member 'trompeloeil::sequence_matcher::exp_name' declared here
  162 |     char const *exp_name;
      |                 ^~~~~~~~
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/sequence.hpp: In instantiation of 'std::__detail::__unique_ptr_t<_Tp> std::make_unique(_Args&& ...) [with _Tp = trompeloeil::sequence_type; _Args = {}; __detail::__unique_ptr_t<_Tp> = __detail::__unique_ptr_t<trompeloeil::sequence_type>]':
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/sequence.hpp:80:74:   required from here
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/sequence.hpp:27:5: warning: 'trompeloeil::sequence_type::matchers' should be initialized in the member initialization list [-Weffc++]
   27 |     sequence_type() noexcept = default;
      |     ^~~~~~~~~~~~~
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/mock.hpp: In instantiation of 'trompeloeil::sequence_handler<N>::sequence_handler() [with long unsigned int M = 0; std::enable_if_t<(M == 0)>* <anonymous> = 0; long unsigned int N = 0]':
/nix/store/9hgsinpfgyvsd92v0wlvmxv9wnaal68r-gcc-13.2.0/include/c++/13.2.0/bits/unique_ptr.h:1070:30:   required from 'std::__detail::__unique_ptr_t<_Tp> std::make_unique(_Args&& ...) [with _Tp = trompeloeil::sequence_handler<0>; _Args = {}; __detail::__unique_ptr_t<_Tp> = __detail::__unique_ptr_t<trompeloeil::sequence_handler<0> >]'
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/lifetime.hpp:137:95:   required from here
/home/sven/projects/trompeloeil-effcpp/build/_deps/trompeloeil-src/include/doctest/../trompeloeil/mock.hpp:1750:5: warning: 'trompeloeil::sequence_handler<0>::matchers' should be initialized in the member initialization list [-Weffc++]
 1750 |     sequence_handler()
      |     ^~~~~~~~~~~~~~~~
[3/3] Linking CXX executable trompeloeil-effcpp-test

The code compiles, but with -Werror the compiler bails out with an error.

See https://github.com/svenihoney/trompeloeil-effcpp for a minimal example project.

[rollbear]

Hmm. I am unable to reproduce this. Where's the difference between your code and my attempt?

https://godbolt.org/z/Escx468z9

[svenihoney]

Hm. Can't reproduce it on godbolt as well, did you try my CMake project?

[svenihoney]

Perhaps try the following:

docker run --rm -it dockcross/linux-x64 bash
git clone https://github.com/svenihoney/trompeloeil-effcpp.git
cmake -B build -S trompeloeil-effcpp/
cmake --build build

and you will get the error.

[rollbear]

I understand where the problem comes from, I was just baffled that my "obvious" reproduction didn't reproduce it and wondered if you could see a mistake.

[rollbear]

Can you try branch Weffc and see if it has resolved your issues?

The warnings about uninitialized member variables are, IMO, incorrect. They are non-trivial types with default constructors that are run at object creation time. Maybe something worth reporting to gcc?

The warnings about default generated operator= were potential bugs, had any future change happened to accidentally call them, so thanks for those.

[rollbear]

No, wait, I spoke too soon. The fix doesn't work with older C++ standards... :disappointed:

[rollbear]

Now the CI pipeline went green for all compilers and standards. Phiew.

[svenihoney]

Perfect, errors are gone!

[rollbear]

Just tagged release v48 which includes this.