According to the following comment:
      /* We cannot inline a function of the form

           void F (int i) { struct S { int ar[i]; } s; }

         Attempting to do so produces a catch-22.
         If walk_tree examines the TYPE_FIELDS chain of RECORD_TYPE/
         UNION_TYPE nodes, then it goes into infinite recursion on a
         structure containing a pointer to its own type.  If it doesn't,
         then the type node for S doesn't get adjusted properly when
         F is inlined.

         ??? This is likely no longer true, but it's too late in the 4.0
         cycle to try to find out.  This should be checked for 4.1.  */

We don't inline functions with variable length types but we should check this out for 4.1 (but it is too late even for 4.1).