[Bug c/127226] New: attribute for marking fields of pointer type that need to be NULL at deallocation

[uecker at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127226

            Bug ID: 127226
           Summary: attribute for marking fields of pointer type that need
                    to be NULL at deallocation
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: uecker at gcc dot gnu.org
  Target Milestone: ---

I would fine an attribute very useful that enables a warning and/or run-time
check when a pointer field is not NULL at the time the parent struct is
deallocated, either because it goes out of scope or because a pointer is passed
to a deallocation function.

struct child;
struct foo {
  [[gnu::clean]] struct child *p; 
};

void bar()
{
  struct foo x = { malloc(sizeof(int); };
  ...

  // child_dellocate(&x.p);  would set x.p to NULL

} // warning if deallocation is missing


This is useful when there are complex data structures with many such children,
and one wants to make sure all are properly deallocated.