Existing GSG violations: non-trivially destructible types at a static storage duration?

[EricCousineau-TRI]

Environment

N/A

Description

• Expected behavior: All static storage duration stuff (static, global const, etc.) should be trivially destructible per GSG
  • https://ignitionrobotics.org/docs/all/contributing#style-guides
  • https://google.github.io/styleguide/cppguide.html#Static_and_Global_Variables
• Actual behavior: It's still a tad mixed atm:

https://github.com/osrf/sdformat/blob/689ee8410a97917e2087ffd5045861d63258ebd4/include/sdf/Types.hh#L64-L72

Steps to reproduce

N/A

Output

N/A

[EricCousineau-TRI]

May not be easiest to fix given that some of these are part of public API.

Some options:

• Using things ilke std::string is important, then make it a function which returns a copy (or even a const reference to) something that is wrap in something like Drake's never_destroyed<> class: https://drake.mit.edu/styleguide/cppguide.html#Static_and_Global_Variables (drake::never_destroyed)
  • Deprecate old spelling.
• Change the type, and just change immediate downstream usages. (Ew).

FYI @azeey @aaronchongth - we came across this in #537