Comment 13 for bug 1935037

> I suggest to define a *small* set of disallowed chars:

I would like to see suggestions expressed in terms of what would be allowed.

Currently this can be expressed as:

> [a-zA-Z_][a-zA-Z0-9_]*

https://github.com/mdavidsaver/pvxs/blob/98edf61de8f2c3d826604d57f7094adbd2a3b308/src/type.cpp#L196

https://github.com/epics-base/pvDataCPP/blob/d3b4976ea2b0d78075511f14d7f7bf9620dd4d14/src/factory/FieldCreateFactory.cpp#L1294