g++ crashes on the following code, while clang++ compiles successfully:

$: cat s.cpp

struct A {};
template <typename T>
struct B
{
    A a;
    friend decltype(a);
};

int main()
{
    A a;
    B<int> b; 
}

$: g++ -std=c++11 -c s.cpp

s.cpp: In instantiation of ‘struct B<int>’:
s.cpp:12:12:   required from here
s.cpp:5:7: internal compiler error: Segmentation fault
    5 |     A a;
      |       ^
0xc6a68f crash_signal
	../../gcc-11-20200628/gcc/toplev.c:328
0x77745a instantiate_class_template_1
	../../gcc-11-20200628/gcc/cp/pt.c:11974
0x778202 instantiate_class_template(tree_node*)
	../../gcc-11-20200628/gcc/cp/pt.c:12098
0x7a7d8d complete_type(tree_node*)
	../../gcc-11-20200628/gcc/cp/typeck.c:137
0x7a7d8d complete_type(tree_node*)
	../../gcc-11-20200628/gcc/cp/typeck.c:111
0x6a031b start_decl_1(tree_node*, bool)
	../../gcc-11-20200628/gcc/cp/decl.c:5490
0x6b0bef start_decl(cp_declarator const*, cp_decl_specifier_seq*, int, tree_node*, tree_node*, tree_node**)
	../../gcc-11-20200628/gcc/cp/decl.c:5453
0x738d3e cp_parser_init_declarator
	../../gcc-11-20200628/gcc/cp/parser.c:20818
0x71c052 cp_parser_simple_declaration
	../../gcc-11-20200628/gcc/cp/parser.c:13785
0x71dbdd cp_parser_declaration_statement
	../../gcc-11-20200628/gcc/cp/parser.c:13217
0x71e7b0 cp_parser_statement
	../../gcc-11-20200628/gcc/cp/parser.c:11523
0x71f5c8 cp_parser_statement_seq_opt
	../../gcc-11-20200628/gcc/cp/parser.c:11889
0x71f680 cp_parser_compound_statement
	../../gcc-11-20200628/gcc/cp/parser.c:11839
0x735280 cp_parser_function_body
	../../gcc-11-20200628/gcc/cp/parser.c:23116
0x735280 cp_parser_ctor_initializer_opt_and_function_body
	../../gcc-11-20200628/gcc/cp/parser.c:23167
0x73887d cp_parser_function_definition_after_declarator
	../../gcc-11-20200628/gcc/cp/parser.c:29063
0x73975f cp_parser_function_definition_from_specifiers_and_declarator
	../../gcc-11-20200628/gcc/cp/parser.c:28979
0x73975f cp_parser_init_declarator
	../../gcc-11-20200628/gcc/cp/parser.c:20722
0x71c052 cp_parser_simple_declaration
	../../gcc-11-20200628/gcc/cp/parser.c:13785
0x741e16 cp_parser_declaration
	../../gcc-11-20200628/gcc/cp/parser.c:13484
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.