[Bug c/127528] [16/17 Regression] ICE: tree check: expected var_decl, have parm_decl in c_mark_addressable, subscripting a flexible array member of a 'register' parameter

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127528

Drea Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2026-11-06

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
GCC 15 and before rejected this:
```
<source>: In function 'c':
<source>:3:25: error: address of register variable 'd' requested
    3 |   int c(register struct s d, int e) { return d.b[e]; }
      |                         ^
<source>:3:7: note: the ABI of passing struct with a flexible array member has
changed in GCC 4.4
    3 |   int c(register struct s d, int e) { return d.b[e]; }
      |       ^
```

The ICE only happens with checking enabled and started sometime during the GCC
16 development.