[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: [tor-bugs] #23368 [Core Tor/Tor]: Add design and coding guidelines for using floating point

#23368: Add design and coding guidelines for using floating point
----------------------------------------------+----------------------------
 Reporter:  teor                              |          Owner:  catalyst
     Type:  enhancement                       |         Status:
                                              |  needs_revision
 Priority:  Medium                            |      Milestone:  Tor:
                                              |  0.3.2.x-final
Component:  Core Tor/Tor                      |        Version:
 Severity:  Normal                            |     Resolution:
 Keywords:  doc, tor-safety, review-group-23  |  Actual Points:
Parent ID:                                    |         Points:  0.5
 Reviewer:                                    |        Sponsor:
----------------------------------------------+----------------------------
Changes (by teor):

 * status:  needs_review => needs_revision


Comment:

 Replying to [comment:9 catalyst]:
 > Proposed patch in https://oniongit.eu/catalyst/tor/merge_requests/1

 Looks great!

 T1. It might help to be more specific here:
 {{{
    - If you must send floating point numbers on the wire, serialize
      them in a platform-independent way. Tor avoids exchanging
      floating-point values. But when it does, it uses ASCII numerals,
      with a decimal point ("."). This is the "C" Locale Format.
 }}}

 For reference, I could only find one floating-point value in all the
 directory documents.
 In extra-info documents, Tor uses the following C code:
 {{{
 printf("epsilon=%.2f", EPSILON_CONSTANT)
 }}}

 Which produces:
 {{{
 epsilon=0.30
 }}}

 T2. I'd also like to add some more notes like this:
 {{{
    - Changing the order of operations changes the results of many
      floating-point calculations. Be careful when you simplify
      calculations! If the order is significant, document it using
      a code comment.
    - Comparing most floating point values for equality is unreliable.
      Avoid using `==`, instead, use `>=` or `<=`.
    - Testing floating-point outputs in unit tests is hard. Tests
      that work on your machine can fail in other environments.
 }}}

 Once you've made these changes, feel free to flip this to "ready to
 merge".

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23368#comment:10>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online

_______________________________________________
tor-bugs mailing list
tor-bugs@xxxxxxxxxxxxxxxxxxxx
https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-bugs