[openssl-users] Warnings Compiling openssl 1.0.2d

[Jeffrey Walton]

On Tue, Jul 21, 2015 at 4:06 PM, Matt Caswell <matt at openssl.org> wrote:
>
>
> On 21/07/15 20:54, Jeffrey Walton wrote:
>>>>                           ^
>>>> d1_both.c: In function 'dtls1_retransmit_message':
>>>> d1_both.c:1261:9: warning: 'save_write_sequence' may be used
>>>> uninitialized in this function [-Wmaybe-uninitialized]
>>>>          memcpy(s->s3->write_sequence, save_write_sequence,
>>>>          ^
>>>
>>> This one is entirely bogus. "save_write_sequence" is initialized on line
>>> 1241. The compiler just isn't clever enough to figure that out.
>>
>> Right. But we need to learn to work with our tools :) The other option
>> throws the baby out with the bath water by disabling warnings. Or, it
>> leaves the problem in places so thousands or millions of folks have to
>> look at the issue and clear it.
>
> Agree to a point. I always config with --strict-warnings to add dev team
> flags (as do the rest of the dev team).

This is a good point. You are saying "trust the developers, they know
what is best." I'm fine with that because they really do know what's
best. No one knows the code better.

... Then C&A creeps in. For some companies, they have to acceptance
test libraries before using them. Its a matter of governance, polices
and procedures. If an organization's bar is lower than OpenSSL's, then
everything is fine. If the bar is higher, then its a pain pint.

Folks like Rich Salz knows exactly what I am talking about and
experiences the pain points regularly. (I've worn Rich's hat and
walked in his shoes).

> We could spend a huge amount of time tracking all of those down for
> little benefit.

To play devil's advocate, To Whom? If 10,000 people each spend 15
minutes looking at (and re-analyzing) one warning, then the community
collectively lost 4,000 man hours. 2 minutes for a dev to clear the
issue once versus 4,000 man hours seems like a very good return on
investment.

And to be fair, I just cleared a similar warning in Crypto++:
https://github.com/weidai11/cryptopp/commit/d04b813e8b078e717992b86b8b6103db0bd2cec3.
I new damn well all those variables were initialized, and the problem
was with analyzer's inter-procedural analysis.

For the d04b813e8 commit, I had to analyze it to ensure it was not a
legitimate squawk. But my choices after analyzing it were: (1) spend
30 seconds on the clear-commit-push cycle; or (2) allow the community
to spend countless hours reanalyzing it, and spend countless hours
explaining the reason for the dirty compile on the mailing list
(q.v.!). I opted for (1) because it was easier on me, and
organizations don't have to worry about C&A and governance issues.

Like I said, its learning to play well with your tools :)

Jeff