[Interest] QMap crash when using QtConcurrent::blockingMapped()

[Konstantin Shegunov]

On Thu, Oct 26, 2017 at 11:11 PM, Jason H <jhihn at gmx.com> wrote:
>
> It sometimes works, sometimes doesn't.


Smells like a race.


> But in my software it seems to come from line 42:
> QList<QVector3D> hp = haystack_points[haystack_item];
>

This may be a write operation, beware of operator [] with maps, notice at
the ends of the docs:

"If the map contains no item with key key, the function inserts a
default-constructed value into the map with key key, and returns a
reference to it."

My advice is to declare your members in `PointsCompare` as const and take
it from there. The compiler will complain, but changing the access (e.g.
using `at()` instead of `[]`) to your members should fix it.

Maybe my use of a class with mapped() is wrong?
>

Not that I could see.
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