PreviewLoader: change 2^(20) to pow(2, 20)?
Scott Kostyshak
skostysh at lyx.org
Sat Mar 28 23:31:32 UTC 2020
On Sat, Mar 28, 2020 at 02:57:31PM -0400, Richard Kimberly Heck wrote:
> On 3/28/20 1:10 PM, Scott Kostyshak wrote:
> > Can someone check whether the attached changes make sense? The first
> > patch just changes the code to what I think is intended. But is it worth
> > it to include the <cmath> header for this one expression or should we
> > put the hardcoded value and in a comment note that it equals 2^20?
> >
> > The second patch increases pow(2, 20) to pow(2, 22), which is
> > PID_MAX_LIMIT on most 64-bit systems, but perhaps there was a reason
> > pow(2, 20) was used? I don't understand the purpose of these fake PIDs
> > so I'm not sure.
>
> How about (1 << 22) + 1, which we use elsewhere?
Nice, indeed more elegant. The adapted patches are in at 8f3c95f7 and
b67ff925.
> We usually track preview processes by their pids, which we get from
> ForkedProcess. But since we are waiting for the result in this case, we
> don't get a real pid (and don't need it), so we just use some arbitrary
> integer.
I see. So we just need a unique identifier. It took me a bit to realize
why we need to be concerned with thread safety but I think I understand
now: even though each buffer has its own preview loader, and even though
we are waiting at this point in the code, it might be that two buffers
are processing previews simultaneously, and the static is shared at the
class level so it is even shared across buffers.
Thanks, Riki.
Scott
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