[Bug c++/99547] New: [11 regression] g++.dg/modules/xtreme-header-5_c.C -std=c++2a ICE

["clyon at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99547

            Bug ID: 99547
           Summary: [11 regression] g++.dg/modules/xtreme-header-5_c.C
                    -std=c++2a ICE
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: clyon at gcc dot gnu.org
  Target Milestone: ---

Between r11-7602 and r11-7616, I've noticed a regression:
FAIL: g++.dg/modules/xtreme-header-5_c.C -std=c++2a (internal compiler error)

on arm-eabi targets, and aarch64-elf (that is, configs using newlib vs glibc
for *linux* targets)

When using -mfloat-abi=hard on arm-eabi, I can see:

/aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-arm-none-eabi/gcc3/gcc/testsuite/g++1/../../xg++
-B/aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-arm-none-eabi/gcc3
/gcc/testsuite/g++1/../../ /gcc/testsuite/g++.dg/modules/xtreme-header-5_c.C
-mcpu=cortex-a7 -mfloat-abi=hard -march=armv7ve+simd -fdiagnostics-plain-output
-nostdinc++

-I/aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-arm-none-eabi/gcc3/arm-none-eabi/thumb/v7ve+simd/hard/libstdc++-v3/include/arm-none-eabi
-I/aci-gcc-fsf/builds/gcc-fsf-gccsrc/
obj-arm-none-eabi/gcc3/arm-none-eabi/thumb/v7ve+simd/hard/libstdc++-v3/include
-I/libstdc++-v3/libsupc++ -I/libstdc++-v3/include/backward
-I/libstdc++-v3/testsuite/util
 -fmessage-length=0 -std=c++2a -pedantic-errors -Wno-long-long -fmodules-ts
-fno-module-lazy -S -o xtreme-header-5_c.s
/gcc/testsuite/g++.dg/modules/xtreme-header-5_c.C:3:30: internal compiler
error: same canonical type node for different types 'void' and
'std::__void_t<decltype ((false ?  declval<typename
std::__match_cv_qualifiers<_From, _To, std::is_const<_Tp>::value,
std::is_volatile<_Tp>::value>::__type& (&)()>()() : declval<typename
std::__match_cv_qualifiers<_Yp, _Xp, std::is_const<_Yp>::value,
std::is_volatile<_Yp>::value>::__type& (&)()>()()))>'
0x97390f comptypes(tree_node*, tree_node*, int)
        /gcc/cp/typeck.c:1555
0x899d4c template_args_equal(tree_node*, tree_node*, bool)
        /gcc/cp/pt.c:9207
0x8998ed comp_template_args(tree_node*, tree_node*, tree_node**, tree_node**,
bool)
        /gcc/cp/pt.c:9254
0x8a6243 spec_hasher::equal(spec_entry*, spec_entry*)
        /gcc/cp/pt.c:1725
0x90e5ae hash_table<spec_hasher, false,
xcallocator>::find_slot_with_hash(spec_entry* const&, unsigned int,
insert_option)
        /gcc/hash-table.h:981
0x8ad6bb add_mergeable_specialization(bool, spec_entry*, tree_node*, unsigned
int)
        /gcc/cp/pt.c:30018
0x80bfb1 trees_in::decl_value()
        /gcc/cp/module.cc:8068
0x80dc47 trees_in::tree_node(bool)
        /gcc/cp/module.cc:9174
0x816a3b module_state::read_cluster(unsigned int)
        /gcc/cp/module.cc:14858
0x816dd4 module_state::load_section(unsigned int, binding_slot*)
        /gcc/cp/module.cc:18129
0x817d37 module_state::read_language(bool)
        /gcc/cp/module.cc:18058
0x81800a direct_import
        /gcc/cp/module.cc:18920
0x88c2b4 cp_parser_translation_unit
        /gcc/cp/parser.c:4905
0x88c2b4 c_parse_file()
        /gcc/cp/parser.c:45241
0xa0a37c c_common_parse_file()
        /gcc/c-family/c-opts.c:1218