Comment 16 for bug 1935037

@Dirk, by "what would be allowed." I meant a positive regex. Omissions are too easy with a negative character set. For example, quote characters.

> WHY?

My main point is that a restricted character makes it easier for future syntax to be designed around PVD field names. Be it CALC expressions in records or in OPI systems like cs-studio.

cf. "pva://SomePVName/subfield/subelement" in cs-studio. Which practically excludes '/' in both record and field names.

https://control-system-studio.readthedocs.io/en/latest/core/pv/doc/index.html#pv-access

As for the specific case of PVXS. Having a different separator for structure and union allows for fewer std::map lookups, giving faster parsing (PVD does a lot of these lookups...).