[Bug analyzer/116006] New: RFE: detect usage of pointers to local variables that are out of scope

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116006

            Bug ID: 116006
           Summary: RFE: detect usage of pointers to local variables that
                    are out of scope
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: dmalcolm at gcc dot gnu.org
  Target Milestone: ---

Consider e.g.:

struct A *extref = something;
...
for (int i = 0; i < n; i++)
{
        struct A intref = *extref;
        intref.memb = i;
        extref = &intref;
}

This is storing a pointer to local variable "intref" into extref.

I think we detect the case where someone tries to use *extref once the function
frame has been popped (via the poisoned_svalue machinery) but I don't think we
detect the case where the usage happens in the same function but outside the
scope of "intref".

Trying it out here: https://godbolt.org/z/6s9WMh53K but I can't seem to trigger
even the popped frame case