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Re: [tor-bugs] #17983 [Tor]: Build tor with -fwrapv by default
#17983: Build tor with -fwrapv by default
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Reporter: teor | Owner:
Type: enhancement | Status: new
Priority: Medium | Milestone: Tor: 0.2.8.x-final
Component: Tor | Version:
Severity: Normal | Resolution:
Keywords: | Actual Points:
Parent ID: | Points:
Sponsor: |
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Comment (by nickm):
I've just heard an alternative proposal: that we should build (most of?)
Tor with -ftrapv rather than -fwrapv.
Rationale: Chandler from the LLVM project looked at wrapping signed
arithmetic in some really huge codebases, to see if there was much buggy
code that assumed that wrapping would happen. What he found instead: that
in (nearly?) every case, no overflow behavior would have been correct: the
code was buggy for any possible semantics of signed overflow. In these
cases, using -fwrapv turns buggy undefined behavior into other buggy (but
defined) behavior, rather than making any code correct.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17983#comment:6>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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