[tor-bugs] #17827 [Tor]: Different return type of backtrace function on FreeBSD

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#17827: Different return type of backtrace function on FreeBSD
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 Reporter:  cypherpunks                |          Owner:
     Type:  defect                     |         Status:  new
 Priority:  Medium                     |      Milestone:  Tor:
Component:  Tor                        |  0.2.8.x-final
 Severity:  Normal                     |        Version:
 Keywords:  027-backport freebsd easy  |     Resolution:
Parent ID:                             |  Actual Points:
  Sponsor:                             |         Points:
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Comment (by teor):

 Replying to [comment:3 cypherpunks]:
 > The FreeBSD versions of `backtrace_symbols` and `backtrace_symbols_fd`
 also expect their `len` parameter to be `size_t`. So we need to make sure
 `depth` is larger than zero to prevent overflow issues.

 We already set MAX_DEPTH to 256, so anything outside the range 0 <= len <=
 MAX_DEPTH is an error. (If that happens, we should probably assert, or
 return from the function.)

 This means that we could use size_t (or long) for len instead of int. Then
 we'd have no shortening warnings.

 We could also change the type of depth in the clean_backtrace arguments,
 and therefore the type of depth in sigsys_debugging.

 I think this is the best way to patch this issue, rather than casting - it
 expresses the intended range of depth / len more clearly than a cast.

 But I'd also happily take a patch that used casts to silence the warnings.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17827#comment:4>
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