[Bug c++/96123] New: [10, trunk] segment fault with NTTP fixed_string

[lutztonineubert at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96123

            Bug ID: 96123
           Summary: [10, trunk] segment fault with NTTP fixed_string
           Product: gcc
           Version: 10.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lutztonineubert at gmail dot com
  Target Milestone: ---

The following code produces a segment fault while compiling with std=c++20 on
GCC 10.1 and trunk.

The problem seems to be the deduction of N in fixed_string.


#include <array>

template<size_t N>
struct fixed_string {
public:
    std::array<char, N> content{};

    constexpr fixed_string(const char (&str)[N]) {
        std::copy(str, str + N - 1, std::begin(content));
    }

    constexpr auto str() const {
        return *this;
    }    
};

template<auto String>
struct string {};

template<template<fixed_string> typename Token = string>
struct to_string {
        template<fixed_string S>
        using type = Token<S.str()>;
};

int main() {
    using x = typename to_string<>::type<"abc">;
}