https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98760
--- Comment #2 from Boris Kolpackov <boris at kolpackov dot net> ---
This still reproduces as of 11.0.1 20210304 (f3641ac70e) though the location
has changed:
hello.cxx:18:25: internal compiler error: in lookup_mark, at cp/tree.c:2403
18 | o << format_hello (n) << std::endl;
| ^
0xde6459 lookup_mark(tree_node*, bool)
../../gcc/gcc/cp/tree.c:2403
0xc5fb19 name_lookup::search_adl(tree_node*, vec<tree_node*, va_gc, vl_embed>*)
../../gcc/gcc/cp/name-lookup.c:1640
0xc5fff5 lookup_arg_dependent(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>*)
../../gcc/gcc/cp/name-lookup.c:1740
0xdadd38 perform_koenig_lookup(cp_expr, vec<tree_node*, va_gc, vl_embed>*, int)
../../gcc/gcc/cp/semantics.c:2507
0xc92a1f cp_parser_postfix_expression
../../gcc/gcc/cp/parser.c:7658
0xc954c2 cp_parser_unary_expression
../../gcc/gcc/cp/parser.c:8818
0xc96bff cp_parser_cast_expression
../../gcc/gcc/cp/parser.c:9722
0xcc3a2c cp_parser_simple_cast_expression
../../gcc/gcc/cp/parser.c:30544
0xc9700f cp_parser_binary_expression
../../gcc/gcc/cp/parser.c:9890
0xc97c01 cp_parser_assignment_expression
../../gcc/gcc/cp/parser.c:10128
0xc97f6f cp_parser_expression
../../gcc/gcc/cp/parser.c:10298
0xc9be7c cp_parser_expression_statement
../../gcc/gcc/cp/parser.c:12012
0xc9b76a cp_parser_statement
../../gcc/gcc/cp/parser.c:11808
0xc9c42e cp_parser_statement_seq_opt
../../gcc/gcc/cp/parser.c:12159
0xc9c2fe cp_parser_compound_statement
../../gcc/gcc/cp/parser.c:12109
0xcb5719 cp_parser_function_body
../../gcc/gcc/cp/parser.c:24029
0xcb5a4c cp_parser_ctor_initializer_opt_and_function_body
../../gcc/gcc/cp/parser.c:24080
0xcc228e cp_parser_function_definition_after_declarator
../../gcc/gcc/cp/parser.c:29997
0xcc20a6 cp_parser_function_definition_from_specifiers_and_declarator
../../gcc/gcc/cp/parser.c:29913
0xcb0156 cp_parser_init_declarator
../../gcc/gcc/cp/parser.c:21602
