specialize cconvert instead of unsafe_convert

[nsajko]

JuliaLang/julia#51962 (comment)

It is generally best to implement cconvert (since it is not unsafe),
and generally required to call both functions as well (mimicking the
behavior defined for ccall)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.26%. Comparing base (c102065) to head (5ea2a1c).

Additional details and impacted files

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##             main      #51   +/-   ##
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  Coverage   98.26%   98.26%           
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  Files           1        1           
  Lines         173      173           
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  Hits          170      170           
  Misses          3        3           

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[giordano]

But the interface documentation says to implement unsafe_convert, no? Maybe that should be fixed?

[nsajko]

But the interface documentation says to implement unsafe_convert, no? Maybe that should be fixed?

Posted a comment at the Julia issue linked above.

[giordano]

Ok, yes, now I start to remember the discussion: MakieOrg/Makie.jl#3661 (comment). The unsafe_convert method is indeed "wrong", but the interface documentation doesn't match that. Also, I see cconvert is allowed not to return an object of type equal to the first argument: https://docs.julialang.org/en/v1/base/c/#Base.cconvert