need to get rid of boost::detail::singleton

[v4hn]

At the moment, your code makes use of boost::detail::singleton in https://github.com/shadow-robot/sr_core/blob/indigo-devel/sr_utilities/include/sr_utilities/sr_math_utils.hpp#L33
I understand the reasoning behind this and I would leave it as it is, but ...
I found a bug in boost 1.60 related to your use-case and the author fixed the problem in boostorg/thread#83 .
However, he didn't even know of these files (which are 14 years old), they are (1.) not used by the project anymore, and (2.) are not part of the public API (that's what boost::detail is for).
So they'll probably go away with the next release even if the maintainer didn't remove them yet.

[guihomework]

Is it possible that this issue does not occur anymore even without the fix of boost 1.60 thanks to this patch f330a04 removing the dependency to future.hpp

Of course when using the patched 1.60 future.hpp will also be fixed.

So the singleton usage could stay as long as it does not disappear from boost

[v4hn]

Is it possible that this issue does not occur anymore even without the fix of boost 1.60 thanks to this patch f330a04 removing the dependency to future.hpp

Could be, I didn't test it recently.

Of course when using the patched 1.60 future.hpp will also be fixed.

My patch there got merged and is released in 1.63, so this bug shouldn't come back to haunt anyone.

So the singleton usage could stay as long as it does not disappear from boost

Well, yes and no. The singleton there is part of ::details - i.e. implementation details - but has not been used throughout the project in a long time. So it is quite likely that it will be removed at some point.