[tor-bugs] #29209 [Core Tor/Tor]: Reduce visibility of more data type internals

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#29209: Reduce visibility of more data type internals
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 Reporter:  nickm                       |          Owner:  (none)
     Type:  task                        |         Status:  needs_review
 Priority:  Medium                      |      Milestone:  Tor:
                                        |  0.4.1.x-final
Component:  Core Tor/Tor                |        Version:
 Severity:  Normal                      |     Resolution:
 Keywords:  technical-debt refactoring  |  Actual Points:  3.5
Parent ID:                              |         Points:  15
 Reviewer:  nickm                       |        Sponsor:  Sponsor31-can
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Comment (by asn):

 I opened #30236 for the crypt_path case.

 I agree that the private approach I took is suboptimal. Here are some
 thoughts about the options above:
 - Option1: I find usin the downcast approach a bit of an overkill here,
 but it might be the right way forward.
 - Option2: I think I like this, it seems quite simple. The only negative
 is that there is no warning if someone uses the private field outside of a
 private file, but I don't think people will attempt to do that with that
 name and macro (and appropriate docs).
 - Option3: I don't think I like this because `#define b PRIV(b)` might
 hijack lots of stuff. So for example, in the crypt_path_t.crypto case we
 would have to do `#define crypto PRIV(crypto)` and that would hijack all
 the cryptos in the file. Also it would be bad form to not capitalize
 `crypto` in that case, and ugly if we did.
 - Option4: This also seems like a plausible one. I'm not sure what `pvt`
 is there tho. I like the fact that it throws a message.

 I think right now I'm leaning more towards option2 for being the most
 lightweight one and easy to understand. What do you think?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29209#comment:6>
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