FHSS timer: Use singleton pointer

[JarkkoPaso]

Description

Use singleton pointer with FHSS timer.

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

Reviewers

[JarkkoPaso]

@kjbracey-arm Can I use singletonptr from array. Seems to work ok with array size of 2.

[kjbracey]

Yes, it's fine to enclose a SingletonPtr as a member of any other static object.

That would only be useful if that static object then becomes a simple object - ie it has no explicit constructor, and its default constructor now has nothing to do because none of its members have explicit constructors - all its complex C++ members are SingletonPtr-wrapped.

[cmonr]

I'm curious. Why was this change needed? All I'm able to find is that a change was made, not why.

[cmonr]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 12 of 12 test jobs passed
Build number : 1
Build artifacts

[0xc0170]

I'm curious. Why was this change needed? All I'm able to find is that a change was made, not why.

can you add this to the commit msg ? what is this addressing.

[JarkkoPaso]

@kjbracey-arm Can you educate us regarding singletonptr?

[kjbracey]

It prevents the static objects always being included in a build. Without the SingletonPtr, blinky would still put those Timer objects in the image to run their constructor, with increased RAM and ROM usage.

If you have any top-level static C++ objects with constructors, wrapping them in SingletonPtr ensures that they are only included in the build if actually used - the constructor is run on first reference, not before main. And if never referenced, it's never constructed, and excluded by the linker altogether.

Tests should have flagged a blinky size increase when those objects were first added.

[JarkkoPaso]

Thanks Kevin! I updated the commit message.

[0xc0170]

CI started

[mbed-ci]

Test run: FAILED

Summary: 1 of 12 test jobs failed
Build number : 3
Build artifacts

Failed test jobs:

• jenkins-ci/mbed-os-ci_greentea-test

[alekla01]

restarted jenkins-ci/greentea-test