[Bug target/81407] New: [avr] Diagnose if a variable in progmem needs constructing.

["gjl at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81407

            Bug ID: 81407
           Summary: [avr] Diagnose if a variable in progmem needs
                    constructing.
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gjl at gcc dot gnu.org
  Target Milestone: ---

avr-g++ might decide to pop up a constructor for a const variable in progmem,
shredding the assumption that the object is not written to at run-time.

Diagnose such situations as the object will reside in .rodata then instead of
in .progmem.data.