[Discuss-gnuradio] fastnoise_source is not thread-safe

[Markus Wirsing]

Hello,

I noticed that the fastnoise_source block is not thread safe, as it
calls rand(), which keeps global state.
This makes it non-reproducable between multiple runs once more than one
such source is used.

I also opened an issue about this on github:
https://github.com/gnuradio/gnuradio/issues/1542
However, there were no reactions to it.

I'm considering to write a fix for it when I find the time.
However, I'm not sure about the requirements that need to be met that it
can later be included in gnuradio.

Would this already require me to have a CRA?
I'm also wondering whether C++11 is allowed in gnuradio.
I guess it is not as I found this message on the mailing list:
https://lists.gnu.org/archive/html/discuss-gnuradio/2014-06/msg00014.html
It might be worth mentioning that on the coding guide in the wiki though:
https://wiki.gnuradio.org/index.php/Coding_guide_impl
It also might be worth considering to change that rule.
C++11 is pretty well supported by now. And it does add some nice features.

I think the easiest fix would be to use random::ran_int() in place of
rand() or lrand48(). That way it would also be possible to get rid of
the (slightly) biased method of using a linear congruence to reduce the
range.

However, while looking at the code in random.cc
https://github.com/gnuradio/gnuradio/blob/master/gnuradio-runtime/lib/math/random.cc
I noticed that it keeps raw pointers to the different random generators.
I don't see why this is done. If I don't misunderstand anything, it
would work equally well to have the objects as members in the class.
With the added benefit of having them correctly deconstructed in the
case of exceptions. Even though that may not be of much relevance in
this case.
But it at least would make sense to use unique pointers instead of raw
pointers.
So if I find the time to create a fix for the other problem, would some
cleanup in this place be appreciated too?

I have no experience so far with submitting code to open source projects.
These issues seem to be a good starting point. However, before investing
time, I want to make sure my work can actually be used.

Appreciating any feedback on the proposed changes and on the necessary
formalities,
Markus