[PATCH STABLE?] parsers: avoid signed integer overflow in calculation of leaf-node index

[Matt Mackall]

On Wed, 2015-04-29 at 23:46 +0900, Yuya Nishihara wrote:
> # HG changeset patch
> # User Yuya Nishihara <yuya at tcha.org>
> # Date 1430316454 -32400
> #      Wed Apr 29 23:07:34 2015 +0900
> # Branch stable
> # Node ID 86a1b0c138484c57501d436efc803c8ad4972928
> # Parent  73b0e11a9cb8fea9b4f0a4ce4267409e8f2054cd
> parsers: avoid signed integer overflow in calculation of leaf-node index
> 
> If v = -INT_MAX - 1, -v would exceed INT_MAX. I don't think this would cause
> problems such as issue4627, but we can't blame it as a compiler bug because
> signed integer overflow is undefined in C.

I guess, queued for stable. I'd like to find a way to make this less
fragile for the caller though. I think it might be cleaner to just
change the comparisons to >= INT_MAX but I haven't had time to think
about it in detail. It doesn't really address the "undefined behavior in
C is REALLY undefined and not just unspecified-but-vaguely-sensible"
problem though.

-- 
Mathematics is the supreme nostalgia of our time.