https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101715
--- Comment #15 from Sergei Trofimovich <slyfox at gcc dot gnu.org> ---
clang's compiler-rt fails to build for quite a while due to this ICE.
Trying to poke at the failure. I shrunk the example slightly further:
template <class A> struct S {
S<A> & bar() noexcept(A::value);
S<A> & foo() noexcept(A::value);
};
template <class A> S<A> & S<A>::foo() noexcept(A::value) {}
c++17 seems to be the trigger (perhaps due to noexcept argument type change?).
Also, if we comment out seemingly unrelated `S::foo()` declaration ICE
disappears. Could it be that there is an unexpected type sharing in an
uninstantiated type?
The backtrace:
$ g++-12.0.0 -c a.c.cpp -std=c++14
$ g++-12.0.0 -c a.c.cpp -std=c++17
a.c.cpp:6:56: internal compiler error: canonical types differ for identical
types 'S<A>& (S<A>::)() noexcept (A::value)' and 'S<A>& (S<A>::)() noexcept
(A::value)'
6 | template <class A> S<A> & S<A>::foo() noexcept(A::value) {}
| ^
0xc3f6ee comptypes(tree_node*, tree_node*, int)
../../gcc-12-20211226/gcc/cp/typeck.c:1558
0xa784ce duplicate_decls(tree_node*, tree_node*, bool, bool)
../../gcc-12-20211226/gcc/cp/decl.c:2409
0xa7f2bb grokfndecl
../../gcc-12-20211226/gcc/cp/decl.c:10351
0xa83cf6 grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
../../gcc-12-20211226/gcc/cp/decl.c:14154
0xa88196 start_function(cp_decl_specifier_seq*, cp_declarator const*,
tree_node*)
../../gcc-12-20211226/gcc/cp/decl.c:17171
0xb82c0f cp_parser_function_definition_from_specifiers_and_declarator
../../gcc-12-20211226/gcc/cp/parser.c:31047
0xb82c0f cp_parser_init_declarator
../../gcc-12-20211226/gcc/cp/parser.c:22520
0xb8a93e cp_parser_single_declaration
../../gcc-12-20211226/gcc/cp/parser.c:31683
0xb8aab6 cp_parser_template_declaration_after_parameters
../../gcc-12-20211226/gcc/cp/parser.c:31243
0xb8b340 cp_parser_explicit_template_declaration
../../gcc-12-20211226/gcc/cp/parser.c:31509
0xb8dcf1 cp_parser_declaration
../../gcc-12-20211226/gcc/cp/parser.c:14849
0xb8e7a2 cp_parser_toplevel_declaration
../../gcc-12-20211226/gcc/cp/parser.c:14939
0xb8e7a2 cp_parser_translation_unit
../../gcc-12-20211226/gcc/cp/parser.c:4987
0xb8e7a2 c_parse_file()
../../gcc-12-20211226/gcc/cp/parser.c:47944
0xcbefcd c_common_parse_file()
../../gcc-12-20211226/gcc/c-family/c-opts.c:1238
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Poking at the internals:
(gdb) fr 1
#1 0x0000000000c3f6ef in comptypes (t1=0x7fffea3791f8, t2=0x7fffea3627e0,
strict=<optimized out>) at ../../gcc-12-20211226/gcc/cp/typeck.c:1557
1557 ../../gcc-12-20211226/gcc/cp/typeck.c: No such file or directory.
(gdb) call debug_generic_expr(t1)
struct S & S::<T385> (struct S *)
(gdb) call debug_generic_expr(t2)
struct S & S::<T37d> (struct S *)
(gdb) call debug_tree(t1)
<method_type 0x7fffea3791f8
type <reference_type 0x7fffea3629d8
type <record_type 0x7fffea362930 S cxx-odr-p type_0 type_5 type_6 VOID
align:8 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7fffea362c78 context <translation_unit_decl 0x7fffea220168 a.c.cpp>
full-name "struct S<A>"
no-binfo use_template=1 interface-unknown
reference_to_this <reference_type 0x7fffea3629d8> chain <type_decl
0x7fffea241b48 S>>
unsigned DI
size <integer_cst 0x7fffea212f48 constant 64>
unit-size <integer_cst 0x7fffea212f60 constant 8>
align:64 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7fffea362f18>
QI
size <integer_cst 0x7fffea234048 type <integer_type 0x7fffea2320a8
bitsizetype> constant 8>
unit-size <integer_cst 0x7fffea234060 type <integer_type 0x7fffea232000
sizetype> constant 1>
align:8 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7fffea3627e0 method basetype <record_type 0x7fffea362c78 S>
arg-types <tree_list 0x7fffea378438
value <pointer_type 0x7fffea362dc8 type <record_type 0x7fffea362c78 S>
unsigned DI size <integer_cst 0x7fffea212f48 64> unit-size
<integer_cst 0x7fffea212f60 8>
align:64 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7fffea362dc8>
chain <tree_list 0x7fffea228b68 value <void_type 0x7fffea232f18 void>>>
throws <tree_list 0x7fffea378410
purpose <scope_ref 0x7fffea3783e8 tree_0 arg:0 <template_type_parm
0x7fffea362888 A>
arg:1 <identifier_node 0x7fffea22e4c0 value
normal local bindings <(nil)>>
a.c.cpp:6:51 start: a.c.cpp:6:51 finish: a.c.cpp:6:55>>>
(gdb) call debug_tree(t2)
<method_type 0x7fffea3627e0
type <reference_type 0x7fffea362f18
type <record_type 0x7fffea362c78 S cxx-odr-p type_0 type_5 type_6 VOID
size <integer_cst 0x7fffea212fc0 constant 0>
unit-size <integer_cst 0x7fffea212f78 constant 0>
align:8 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7fffea362c78 fields <using_decl 0x7fffea241a18 operator=> context
<translation_unit_decl 0x7fffea220168 a.c.cpp>
full-name "struct S<A>"
n_parents=0 use_template=0 interface-unknown
pointer_to_this <pointer_type 0x7fffea362dc8> reference_to_this
<reference_type 0x7fffea362f18> chain <type_decl 0x7fffea2418e8 S>>
unsigned type_0 type_6 DI
size <integer_cst 0x7fffea212f48 constant 64>
unit-size <integer_cst 0x7fffea212f60 constant 8>
align:64 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7fffea362f18>
type_0 type_6 QI
size <integer_cst 0x7fffea234048 type <integer_type 0x7fffea2320a8
bitsizetype> constant 8>
unit-size <integer_cst 0x7fffea234060 type <integer_type 0x7fffea232000
sizetype> constant 1>
align:8 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7fffea362540 method basetype <record_type 0x7fffea362c78 S>
arg-types <tree_list 0x7fffea35cf28
value <pointer_type 0x7fffea362dc8 type <record_type 0x7fffea362c78 S>
unsigned DI size <integer_cst 0x7fffea212f48 64> unit-size
<integer_cst 0x7fffea212f60 8>
align:64 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7fffea362dc8>
chain <tree_list 0x7fffea228b68 value <void_type 0x7fffea232f18 void>>>
throws <tree_list 0x7fffea378230
purpose <scope_ref 0x7fffea378208 tree_0 arg:0 <template_type_parm
0x7fffea362bd0 A>
arg:1 <identifier_node 0x7fffea22e4c0 value
normal local bindings <(nil)>>
a.c.cpp:3:30 start: a.c.cpp:3:30 finish: a.c.cpp:3:34>>>
If I read the difference correctly `t1` has no `operator=` field while `t2`
has.
