AW: [PATCH] soc: aspeed: fix a ternary sign expansion bug
David.Laight at ACULAB.COM
Sat Apr 24 00:55:29 AEST 2021
From: Sergey Organov
> Sent: 23 April 2021 15:40
> Walter Harms <wharms at bfs.de> writes:
> > as indepentent observer,
> > i would go for Dans solution:
> > ret = kfifo_to_user();
> > /* if an error occurs just return */
> > if (ret)
> > return ret;
> > /* otherwise return the copied number of bytes */
> > return copied;
> > there is no need for any deeper language knowledge,
> Yep, but this is not idiomatic C, so one looking at this code would
> tend to convert it back to ternary, and the actual problem here is that
> the type of 'copied' does not match the return type of the function.
Actually changing the type of 'ret' to ssize_t is probably
the safest change.
That works until someone tries to optimise out 'ret' by doing:
return kfifo_to_user(...) ?: count;
Or rattle through and remove the 'pass by reference' 'count'
parameter from kfifo_to_user() in favour of returning the
value the callers want.
I need to stop looking at this code :-)
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