[Bug c/116194] New: enhancement: attribute to protect tagged unions

[uecker at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116194

            Bug ID: 116194
           Summary: enhancement: attribute to protect tagged unions
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: uecker at gcc dot gnu.org
  Target Milestone: ---

An attribute that can be attached to tagged unions that traps when a non-active
field is accesses.

One option may be a generic attribute that specifies a condition that needs to
be fulfilled on access of a field.

struct {
  enum { A, B } tag;
  union {
    int a [[guard(.tag == A)]];
    float b [[guard(.tag == B]];
  };
};