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Date: Wed, 13 Jun 2012 19:32:48 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: FreeSec crypt()
* Solar Designer <solar@...nwall.com> [2012-06-13 20:45:46 +0400]:
> On Wed, Jun 13, 2012 at 10:56:03AM -0400, Rich Felker wrote:
> > Well if char is signed, (char)0x80 << 1 is -256. If char is unsigned,
> > (char)0x80 << 1 is 256.
>
> Sure, but we had:
>
> const char *key;
> u_char *q;
> *q++ = *key << 1;
>
> so while *key << 1 is either -256 or 256 (promoted to int or unsigned
> int), those high bits get dropped on the assignment to *q anyway,
> resulting in the same value there either way. No?
yes the code happens to work whenever -128<<1 is -256
and i assume -256 is what most compilers will give
usually in case of two's complement int representation
but -128<<1 is UB and should be fixed anyway
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