Hi guys,
May I know why the compilation failed for the following code where the
compiler is complaining that `s` is not a constant expression? While
removing the `static_assert`, the compilation passed. Regards.
1 #include <array>
2 #include <string_view>
3 #include <cstddef>
4
5 template<std::size_t N>
6 constexpr std::array<int, N> test(std::string_view s)
7 {
8 static_assert(s.size() > N);
9 return { 0 };
10 }
11
12 int main(int argc, char *argv[])
13 {
14 using namespace std::literals;
15 constexpr auto s = "123"sv;
16 constexpr auto a = test<2>(s);
17 return 0;
18 }
The g++ version being used is g++-14 (Homebrew GCC 14.2.0_1) 14.2.0.
Error messages:
test.cpp: In instantiation of 'constexpr std::array<int, N>
test(std::string_view) [with long unsigned int N = 2; std::string_view
= std::basic_string_view<char>]':
test.cpp:16:29: required from here
16 | constexpr auto a = test<2>(s);
| ~~~~~~~^~~
test.cpp:8:26: error: non-constant condition for static assertion
8 | static_assert(s.size() > N);
| ~~~~~~~~~^~~
In file included from test.cpp:2:
test.cpp:8:23: in 'constexpr' expansion of
's.std::basic_string_view<char>::size()'
/opt/homebrew/Cellar/gcc/14.2.0_1/include/c++/14/string_view:230:22:
error: 's' is not a constant expression
230 | { return this->_M_len; }
| ~~~~~~^~~~~~
