i think freepascal devs or community have to try to define a new, completely new language subset, which compiler would check with some switch.
No. Neither we devs nor the community
has to try anything here. We're already hard at work catching up with Delphi's features which is a very much community driven demand plus the support of the two Pascal standards for the sake of completeness and bragging points. Adding an additional, new, more restricted language dialect would result in unnecessary work and complication and the target audience would probably be even smaller than those that currently use mode
ISO and look forward to a fully supported mode
ExtPas.
but i think that fpc community and/or devs are the people who can agree on some minimalistic and safe features for clean design of new pascal language subset.
No. We don't agree on that. Even among us devs there is the division between those that defend the
ObjFPC dialect (which
is at least a bit more strict than mode
Delphi) and those that would like to see it gone (though that will never happen due to our stance on backwards compatibility).
the good thing it won't require much changes, or introduction of new features. it would only require a limitation of feature usage by a commandline switch.
It would nevertheless complicate the parser even more, because each added modeswitch requires checking after all.