quality: improve warning flags and fix issues

[VDanielEdwards]

Subject

Enables more warning flags for GCC and fixes resulting issues.

Developer checklist (address before review)

• Changelog.md updated
• Prepared update for depending repositories
• Documentation updated (public API changes only)
• API docstrings updated (public API changes only)
• Rebase → commit history clean
• Squash and merge → proper PR title

[MariusBgm]

LGTM

[VDanielEdwards]

Do you see any issues on your end regarding the changes in warning flags?

You'll only have to take a look at this commit - the other changes are just fixing stuff found through additional warnings.

@snps-fricke

[snps-behrens]

Interestingly, these changes cause gcc12.3 to run into a free-nonheap-object warning. The warning is not hit by gcc9.5 or gcc13.2 (the two other compiler versions I tested), and is only hit when compiling with build type Release and not when compiling with Debug.

GCC error:

```sh In file included from .../gcc/12.3/include/c++/12.3.0/x86_64-pc-linux-gnu/bits/c++allocator.h:33, from .../gcc/12.3/include/c++/12.3.0/bits/allocator.h:46, from .../gcc/12.3/include/c++/12.3.0/string:41, from .../gcc/12.3/include/c++/12.3.0/stdexcept:39, from .../sil-kit/SilKit/include/silkit/participant/exception.hpp:7, from .../sil-kit/SilKit/include/silkit/SilKit.hpp:8, from .../sil-kit/Demos/communication/include/ApplicationBase.hpp:5, from .../sil-kit/Demos/communication/Rpc/RpcServerDemo.cpp:5: In member function 'void std::__new_allocator<_Tp>::deallocate(_Tp*, size_type) [with _Tp = unsigned char]', inlined from 'static void std::allocator_traits >::deallocate(allocator_type&, pointer, size_type) [with _Tp = unsigned char]' at .../gcc/12.3/include/c++/12.3.0/bits/alloc_traits.h:496:23, inlined from 'void std::_Vector_base<_Tp, _Alloc>::_M_deallocate(pointer, std::size_t) [with _Tp = unsigned char; _Alloc = std::allocator]' at .../gcc/12.3/include/c++/12.3.0/bits/stl_vector.h:387:19, inlined from 'std::_Vector_base<_Tp, _Alloc>::~_Vector_base() [with _Tp = unsigned char; _Alloc = std::allocator]' at .../gcc/12.3/include/c++/12.3.0/bits/stl_vector.h:366:15, inlined from 'std::vector<_Tp, _Alloc>::~vector() [with _Tp = unsigned char; _Alloc = std::allocator]' at .../gcc/12.3/include/c++/12.3.0/bits/stl_vector.h:733:7, inlined from 'RpcServer::CreateControllers()::' at .../sil-kit/Demos/communication/Rpc/RpcServerDemo.cpp:86:9: .../gcc/12.3/include/c++/12.3.0/bits/new_allocator.h:158:33: error: 'void operator delete(void*, std::size_t)' called on pointer '' with nonzero offset [1, 4294967295] [-Werror=free-nonheap-object] 158 | _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n)); | ^ In member function '_Tp* std::__new_allocator<_Tp>::allocate(size_type, const void*) [with _Tp = unsigned char]', inlined from 'static _Tp* std::allocator_traits >::allocate(allocator_type&, size_type) [with _Tp = unsigned char]' at .../gcc/12.3/include/c++/12.3.0/bits/alloc_traits.h:464:28, inlined from 'std::_Vector_base<_Tp, _Alloc>::pointer std::_Vector_base<_Tp, _Alloc>::_M_allocate(std::size_t) [with _Tp = unsigned char; _Alloc = std::allocator]' at .../gcc/12.3/include/c++/12.3.0/bits/stl_vector.h:378:33, inlined from 'void std::_Vector_base<_Tp, _Alloc>::_M_create_storage(std::size_t) [with _Tp = unsigned char; _Alloc = std::allocator]' at .../gcc/12.3/include/c++/12.3.0/bits/stl_vector.h:395:44, inlined from 'std::_Vector_base<_Tp, _Alloc>::_Vector_base(std::size_t, const allocator_type&) [with _Tp = unsigned char; _Alloc = std::allocator]' at .../gcc/12.3/include/c++/12.3.0/bits/stl_vector.h:332:26, inlined from 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp = unsigned char; _Alloc = std::allocator]' at .../gcc/12.3/include/c++/12.3.0/bits/stl_vector.h:598:61, inlined from 'RpcServer::CreateControllers()::' at .../sil-kit/Demos/communication/Rpc/RpcServerDemo.cpp:72:57: .../gcc/12.3/include/c++/12.3.0/bits/new_allocator.h:137:55: note: returned from 'void* operator new(std::size_t)' 137 | return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp))); | ^ ```

This is not a big deal for us at this point in time, as we are currently using gcc9.5 as our primary compiler for SilKit. However, anybody that uses gcc12.3 (and maybe even other minor versions of gcc12; I didn't test any others) would probably run into this same warning/error. On the other hand, this seems like it might actually be a bug in that version of gcc, as older and newer versions of gcc do not produce the warning, so it might not be worth 'fixing' in the SilKit code base. What are your thoughts @snps-fricke @VDanielEdwards ?

We are also still seeing some -Wuseless-cast warnings coming out of the oatpp compilation when using gcc (independent of compiler version), and some C4068: unknown pragma 'GCC' warnings coming out of MSVC (tried with toolchain versions 14.29 (VS2019) and 14.34 (VS2022)). Would it be sensible to explicitly turn those warnings off for that submodule in the ThirdParty CMake, similar to how it is already done with /wd4244 for MSVC?