Add missing export markers (OTIO_API) for constructors

[jlskuz]

This is a follow up to #1953
I am working on MSVC support for Kdenlive (currently MinGW is used for Windows) and hit

kdenliveLib.lib(otioexport.cpp.obj) : error LNK2019: unresolved external symbol "public: __cdecl opentimelineio::v0_18_1::GeneratorReference::GeneratorReference(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &,class std::optional<class opentime::v0_18_1::TimeRange> const &,class opentimelineio::v0_18_1::AnyDictionary const &,class opentimelineio::v0_18_1::AnyDictionary const &,class std::optional<class Imath_3_1::Box<class Imath_3_1::Vec2<double> > > const &)" (??0GeneratorReference@v0_18_1@opentimelineio@@QEAA@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@0AEBV?$optional@VTimeRange@v0_18_1@opentime@@@4@AEBVAnyDictionary@12@2AEBV?$optional@V?$Box@V?$Vec2@N@Imath_3_1@@@Imath_3_1@@@4@@Z) referenced in function "private: void __cdecl OtioExport::exportClip(class std::shared_ptr<class TimelineItemModel> const &,struct OtioExport::ClipData const &,struct opentimelineio::v0_18_1::SerializableObject::Retainer<class opentimelineio::v0_18_1::Track> &)" (?exportClip@OtioExport@@AEAAXAEBV?$shared_ptr@VTimelineItemModel@@@std@@AEBUClipData@1@AEAU?$Retainer@VTrack@v0_18_1@opentimelineio@@@SerializableObject@v0_18_1@opentimelineio@@@Z)
bin\cachetest.exe : fatal error LNK1120: 1 unresolved externals 

this brought to my attention that only some classes have OTIO_API on their constructors, while others, such as GeneratorReference, have not causing the above failure. As far as I understand all of these classes and ctors are public API however (please check and confirm) and hence should have OTIO_API.

@darbyjohnston Was #1953 just in complete or did you only add it to certain classes on purpose? This does probably not only affect the ctors, but also other class members. Should I add OTIO_API to all of them (either here or in a seperate PR)? Is it safe to assume that everything in the public: section of src/opentimelineio/*.h files is public api and hence should have OTIO_API?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.13%. Comparing base (2429dd5) to head (19698db).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1992   +/-   ##
=======================================
  Coverage   85.13%   85.13%           
=======================================
  Files         181      181           
  Lines       12783    12783           
  Branches     1206     1206           
=======================================
  Hits        10883    10883           
  Misses       1717     1717           
  Partials      183      183           

Flag	Coverage Δ
py-unittests	85.13% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/opentimelineio/effect.h	80.00% <ø> (ø)
src/opentimelineio/errorStatus.h	100.00% <100.00%> (ø)
src/opentimelineio/generatorReference.h	50.00% <ø> (ø)
src/opentimelineio/imageSequenceReference.h	56.52% <ø> (ø)

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[darbyjohnston]

Hi @jlskuz, thanks for catching this, there definitely may have been places I missed adding the exports. I think the rule of thumb was all member functions that are not inline, but all of the details are here:
https://github.com/PixarAnimationStudios/OpenUSD/blob/dev/pxr/base/arch/export.h

Were you seeing errors about the ErrorStatus class?

[jlskuz]

No, I did not see an error about the ErrorStatus class. The only real world issue I saw with Kdenlive was related to GeneratorReference

[darbyjohnston]

I was wondering because it looks like the ErrorStatus members are inline, which I didn't think needed the export decorations (inline makes them visible by default).

[jlskuz]

Oh, yes I confused at least one operator with a conatructor

[darbyjohnston]

Maybe remove the exports from the ErrorStatus constructors and operators, otherwise this looks good to me.