[WIP] add submodule for C bindings, library compilation with PackageCompiler

[m-fila]

Adding C bindings and ahead of time compilation to shared library with PackageCompiler.jl

C components have jetreconstruction_(or JETRECONSTRUCTION_) prefix

For now the C API includes only:

• jet_reconstruct
• exclusive_jets, inclusive_jets
• enums and structs used in their signatures. When needed new structs with C-like layout are introduced (for instance replacing Vector{T} field with Ptr{T} and Csize_t fields for C-facing structs)

The C header file has to be written manually and keep in sync with Julia code. Technically the whole compile could be a separate julia package possibly eveb living in a separate repo, but I think it'd be harder to keep in sync this way

---

To do:

• write to an output pointer from inclusive_jets and exclusive_jets
• add error handling
• support Lorentz vectors
• add missing docstrings
• add precompilation statements
• cache all combinations of strategy and algorithm in procompilation
• use PseudoJet for pp and EEJet for ee algorithms
• have actual test
• install JetReconstructionConfig.cmake?
• compilation with upcoming juliac?
  - [ ] add c-style building (make/CMake)?

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 98 lines in your changes missing coverage. Please review.

Project coverage is 67.78%. Comparing base (164c6d2) to head (761c247).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/C_JetReconstruction/C_JetReconstruction.jl	0.00%	98 Missing ⚠️

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Flag	BASE (164c6d2)	HEAD (761c247)
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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #88      +/-   ##
==========================================
- Coverage   73.49%   67.78%   -5.72%     
==========================================
  Files          18       19       +1     
  Lines        1249     1341      +92     
==========================================
- Hits          918      909       -9     
- Misses        331      432     +101     

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[m-fila]

The CI for Julia 1.9 fails as documenting@ccallable functions was fixed only in 1.11 😢

I couldn't think of a good way of error handling.
What I propose here is to:

• use status codes from enum with:
  • value for success,
  • values for each standard Julia exception,
  • single value for the remaining cases.
• print the exception and backtrace to stderr so it's not lost

I also couldn't find a reasonable way to translate Julia exceptions to C++ exceptions without going through C-bottleneck

[Moelf]

We don't need to support 1.9 I guess, but I hope we can backport JuliaLang/julia#51587 to 1.10.

[graeme-a-stewart]

Yeah, I would agree we can drop support for 1.9 now, but the LTS release (1.10) we should try to support

[graeme-a-stewart]

Just report this crashes on OS X with

[ Info: PackageCompiler: Executing /Users/graemes/.julia/dev/JetReconstruction/compile/precompile_execution.jl => /var/folders/kq/jgwv_wcj3ll2n6qwj06pp6jr0000gn/T/jl_packagecompiler_0hx01x/jl_dsyOUt
julia(84816,0x1f264cf40) malloc: *** error for object 0x134add910: pointer being freed was not allocated
julia(84816,0x1f264cf40) malloc: *** set a breakpoint in malloc_error_break to debug

[84816] signal 6: Abort trap: 6
in expression starting at /Users/graemes/.julia/dev/JetReconstruction/compile/precompile_execution.jl:33

I'm investigating!

[m-fila]

Thanks for checking. I think that was because the results_ptrpointee was managed by Julia and got garbage collected. Should be fixed now

[graeme-a-stewart]

Yes, now it works - thanks for the quick fix @m-fila!