[Bug c++/80667] New: [c++1z] ice segfault on partial specialization with non-type template parameter

[mathias at gaunard dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80667

            Bug ID: 80667
           Summary: [c++1z] ice segfault on partial specialization with
                    non-type template parameter
           Product: gcc
           Version: 7.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mathias at gaunard dot com
  Target Milestone: ---

Building the following code with std=c++1z

#include <type_traits>

template<class T>
struct traits
{
    static constexpr T const_min = 0;
};

template <typename T, typename>
class Impl;

template<typename T, T MaxValue>
struct Impl<T, std::integral_constant<T, MaxValue>>
{
};

template<typename T>
struct Impl<T, std::integral_constant<T, traits<T>::const_min>>
{
};

Impl<unsigned char, std::integral_constant<unsigned char, 0>> foo()
{
    return {};
}

gives

test.cpp: In function ‘Impl<unsigned char, std::integral_constant<unsigned
char, 0> > foo()’:
test.cpp:22:67: internal compiler error: Segmentation fault
 Impl<unsigned char, std::integral_constant<unsigned char, 0>> foo()
                                                                   ^
0xb118ef crash_signal
        ../../gcc-src/gcc/toplev.c:337
0x61b925 unify
        ../../gcc-src/gcc/cp/pt.c:20292
0x61c8d1 unify
        ../../gcc-src/gcc/cp/pt.c:20573
0x61c319 unify
        ../../gcc-src/gcc/cp/pt.c:20764
0x61c4d7 unify
        ../../gcc-src/gcc/cp/pt.c:20843
0x61c319 unify
        ../../gcc-src/gcc/cp/pt.c:20764
0x61d971 get_partial_spec_bindings
        ../../gcc-src/gcc/cp/pt.c:21561
0x61db83 more_specialized_partial_spec
        ../../gcc-src/gcc/cp/pt.c:21436
0x61ddd9 most_specialized_partial_spec
        ../../gcc-src/gcc/cp/pt.c:21856
0x62e66b instantiate_class_template_1
        ../../gcc-src/gcc/cp/pt.c:10230
0x62e66b instantiate_class_template(tree_node*)
        ../../gcc-src/gcc/cp/pt.c:10798
0x691e75 complete_type(tree_node*)
        ../../gcc-src/gcc/cp/typeck.c:133
0x5ecffc check_function_type
        ../../gcc-src/gcc/cp/decl.c:14662
0x5ecffc start_preparsed_function(tree_node*, tree_node*, int)
        ../../gcc-src/gcc/cp/decl.c:14883
0x6000f3 start_function(cp_decl_specifier_seq*, cp_declarator const*,
tree_node*)
        ../../gcc-src/gcc/cp/decl.c:15199
0x686c97 cp_parser_function_definition_from_specifiers_and_declarator
        ../../gcc-src/gcc/cp/parser.c:26129
0x686c97 cp_parser_init_declarator
        ../../gcc-src/gcc/cp/parser.c:19159
0x68796d cp_parser_simple_declaration
        ../../gcc-src/gcc/cp/parser.c:12777
0x688575 cp_parser_block_declaration
        ../../gcc-src/gcc/cp/parser.c:12602
0x666ec4 cp_parser_declaration
        ../../gcc-src/gcc/cp/parser.c:12500
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.

Works fine without std=c++1z, alternatively a workaround is to add a cast in
the second partial specialization.