Add support for modular build structure.

[grafikrobot]

This is part of the effort to make the Boost libraries "modular" for build and consumption. See https://lists.boost.org/Archives/boost/2024/01/255704.php and https://github.com/grafikrobot/boost-b2-modular/blob/b2-modular/README.adoc for more information.

This PR depends on the following other PRs being merged to both develop and master branches of the respective repos:

• Add support for modular build structure. boost#854

This PR will be changed to ready for review, i.e. not draft, when the above are merged. Do not merge this one until that time.

[grafikrobot]

Please review and merge this PR at your earliest convenience.

[grafikrobot]

Regarding the CI failures..

1. MacOS fails with: test/tensor/tensor/test_tensor_operator_arithmetic_binary.cpp:58: error: in "test_tensor_binary_arithmetic/test_tensor_dynamic<std____1__pair<float_ boost__numeric__ublas__basic_column_major>>": check r(i) == t2(i) / (t1(i)+three)*(t1(i)+one) - t2(i) has failed [-1.71428585 != -1.71428561] -- Which looks like a library issue, and nothing I can do about it.
2. Clang Sanitizer fails building file_system lib with many errors of: undefined reference to `__ubsan_handle_type_mismatch_v1' -- I'll see if I can fix that, and add it to the various other CI fixes I've done.
3. Linux fails with a bunch of constexpr compile errors. Nothing related to this PR.
4. Windows fails with a variety of compile errors. The library probably needs to be looked at for msvc latest compatibility issues?

I'll investigate 2 further. But everything else someone else would need to deal with. And I suspect it's all existing issues unrelated to this PR.

[Becheler]

Hope that helps a bit 😅

[Becheler]

../../../boost/numeric/ublas/tensor/extents/extents_static_size.hpp:74:5: note: non-constexpr function 'copy<const unsigned long *, unsigned long *>' cannot be used in a constant expression
    std::copy(li.begin(), li.end(), _base.begin());

Ubuntu 20.04 ships with libstdc++9, where std::copy is not constexpr:

run: sudo apt-get update && sudo apt-get install -y clang-10 libstdc++-10-dev

[Becheler]

run: sudo apt-get update && sudo apt-get install -y clang-11 libstdc++-10-dev
Ubuntu 20.04 ships with libstdc++9, where std::copy is not constexpr

[Becheler]

test/tensor/tensor/test_tensor_operator_arithmetic_binary.cpp:58: error: in
"test_tensor_binary_arithmetic/test_tensor_dynamic<std____1__pair<float_ boost__numeric__ublas__basic_column_major<unsigned long_ long>>>":
check r(i) == t2(i) / (t1(i)+three)*(t1(i)+one) - t2(i) has failed [-1.71428585 != -1.71428561]

The tests execute for the first time in years, now on arm64 and much newer compilers so suddenly FMA contraction breaks the float equality check in test_tensor_operator_arithmetic_binary.cpp:58

Maybe use -ffp-contract=off ? :

      <toolset>gcc:<cxxflags>"-Wall -Wno-unknown-pragmas -Wno-sign-compare -Wno-unused-but-set-variable -ffp-contract=off"
      <toolset>clang:<cxxflags>"-Wall -Wno-unknown-pragmas -Wno-sign-compare -ffp-contract=off"

[Becheler]

expression_evaluation.hpp(240): error C2678: binary '!=': no operator found which takes a
  left-hand operand of type 'const boost::numeric::ublas::extents_core<unsigned __int64>'
  (or there is no acceptable conversion)

One more possible fix:

ublas/include/boost/numeric/ublas/tensor/expression_evaluation.hpp

Lines 237 to 241 in 8708cbf

	using ::operator==;
	if constexpr ( std::is_same<T,E>::value )
	if(e != expr.e.extents())
	return false;

develop pins windows-2019, the PR adds windows-2022 with msvc 14.3 resolving to 14.44. 14.44 no longer treats the block-scope using ::operator==; as a rewrite candidate for !=:

• CE with MSVC 19.29 c++ latest runs fine: https://godbolt.org/z/883ejfWo3
• CE with MSVC 19.44 c++ latest errors: https://godbolt.org/z/dbbf91T8n
• adding using ::operator!=; works again: https://godbolt.org/z/jojErv49b

[grafikrobot]

Another bit of investigation.. The UBsan errors for filesystem appear to be actual UB in that library.

[Becheler]

@grafikrobot look at boostorg/filesystem@3e94c81

Remove sanitizer compiler flags when checking for -Wl,--no-undefined.
Clang has a bug (llvm/llvm-project#60578)
where it doesn't add sanitizer runtime libraries to linker flags, which
results in linking errors when -Wl,--no-undefined or equivalent is used.
We want to know if -Wl,--no-undefined is supported, so to avoid false
negatives remove any sanitizer flags for this check. Users will have to
explicitly specify sanitizer libraries in their linker flags to work
around the clang bug.

Do you think adding ldflags: -shared-libsan on the sanitizer job could work ?

[grafikrobot]

Do you think adding ldflags: -shared-libsan on the sanitizer job could work ?

Did not help.. error while loading shared libraries: libclang_rt.ubsan_standalone-x86_64.so.

[Becheler]

@grafikrobot I tried those fixes over your PR : bd7392c

and it results in a green CI: #200

I don't know how you want to proceed, you can cherry pick the commit maybe ?

[Becheler]

Thank you all ! 🥳