Static members got failed to compile

Asked May 28 '21 at 07:20

Active May 28 '21 at 07:20

Viewed 46 times

I'm trying to understand what the compiler complains and how to follow rules by C++. I very appreciate any help

#include <string>
struct Foo {
  static const char* BAR = "Bar"; // -> Not okay
  static constexpr const char* FOO = "Foo"; // okay
  static std::string s_; //-> okay
  static constexpr std::string s("sss"); // not okay
};

std::string Foo::s_ = "sss";

int main()
{
    return 0;
}

Out:

error: ‘constexpr’ needed for in-class initialization of static data member ‘const char* Foo::BAR’ of non-integral type [-fpermissive]
   static const char* BAR = "Bar"; // -> Not okay
                      ^~~
test.cc:6:40: error: expected identifier before string constant
   static constexpr std::string s("sss"); // not okay
                                        ^~~~~
test.cc:6:40: error: expected ‘,’ or ‘...’ before string constant

asked May 28 '21 at 07:20

nhatnq

1,173
7
16

1

Also the reason why `static constexpr std::string s("sss");` doesn't work is that `std::string` can't be constexpr (prior to C++20). See https://stackoverflow.com/q/27123306/6205379 for more details on that. – Timo May 28 '21 at 07:26
String literal cannot convert to `const char *`. – rawrex May 28 '21 at 07:28
@rawrex Yes, it can. – molbdnilo May 28 '21 at 07:30
@molbdnilo as in the OP code? – rawrex May 28 '21 at 07:33
@molbdnilo yeah, I see. Commented right of the bat, so my bad if I was being misleading. – rawrex May 28 '21 at 07:39
@molbdnilo thought if we'll take away the `s`, it still won't compile, as you know. – rawrex May 28 '21 at 07:41

Static members got failed to compile

0 Answers0