https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127528
Bug ID: 127528
Summary: [17 Regression] ICE: tree check: expected var_decl,
have parm_decl in c_mark_addressable, subscripting a
flexible array member of a 'register' parameter
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Keywords: ice-on-valid-code
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: captainnemo9292 at gmail dot com
Target Milestone: ---
Target: x86_64-linux-gnu
Valid (if odd) C:
struct s { int n; int b[]; };
int c(register struct s d, int e) { return d.b[e]; }
$ gcc -c t.c
t.c:2:23: internal compiler error: tree check: expected var_decl, have
parm_decl in c_mark_addressable, at c/c-typeck.cc:6574
tree_check_failed
build_array_ref(unsigned long, tree_node*, tree_node*)
c_parse_file()
https://godbolt.org/z/YoGvfKoMM
Subscripting an array member requires taking the address of the
register-qualified struct, so build_array_ref calls c_mark_addressable. The
'register' branch there uses a VAR_DECL-only accessor (c-typeck.cc:6574),
but the object is a PARM_DECL. A fixed-size member (int b[4]) ICEs the same
way. gcc 13 rejects both with "address of register variable 'd' requested",
so this is a trunk regression.
