[vlc-devel] [PATCH] vlc_strftime: avoid infinite loop on windows when format string is invalid

Rémi Denis-Courmont remi at remlab.net
Thu Jan 25 19:10:26 CET 2018

Le torstaina 25. tammikuuta 2018, 19.35.55 EET Romain Vimont a écrit :
> On Thu, Jan 25, 2018 at 06:43:42PM +0200, Rémi Denis-Courmont wrote:
> > We can intrinsically not handle UB and therefore we do not handle UB, at
> > least not post-facto. Where practical and useful, you can add post-facto
> > assertions to aid in debugging - nothing else.
> I agree with you, in theory we can just ignore UB.

I did not state that we CAN ignore UB. I stated that we MUST ignore UB.
By definition.

After UB, the only thing that vaguely makes sense is aborting, typically done 
with assert().

> But here, the current vlc_strftime() implementation may transform an
> error (with errno set) to an infinite loop, which is not very
> debug-friendly.

UB is not debug-friendly in the first place and clobbering errno is not 
friendly to debug and tracing either.

> To always avoid an infinite loop, one possibility could be to double the
> buffer size on each iteration (instead of increasing linearly), and
> limit to, say, 10 iterations, failing with an error otherwise.

We already handle the empty string case.


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