Re: Undefined symbol error for static const char

From:

Michael Doubez <michael.doubez@free.fr>

Newsgroups:

comp.lang.c++

Date:

Thu, 8 Oct 2009 06:12:51 -0700 (PDT)

Message-ID:

<5a5bf446-6102-4fdd-8902-c86b110fef17@g6g2000vbr.googlegroups.com>

On 8 oct, 13:44, p...@informatimago.com (Pascal J. Bourguignon) wrote:

rawhm <simbut...@live.com> writes:

What gives?

$ cat sc.cpp

#include <vector>

class cls {
public:
    static const char foo = 100;
};

int main(int argc, char **argv) {
    std::vector<char> vect;

    vect.resize(10, cls::foo);

    return 0;
}

$ g++ sc.cpp

Undefined symbols:
"cls::foo", referenced from:
__ZN3cls3fooE$non_lazy_ptr in ccB49b7c.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

Anotherway to write it seems to be:

class cls {
public:
static const char foo;};

const char cls::foo = 100;

and both ways are accepted by my compiler (gcc 4.4.1)

This is an error in the OP version, it only declares the static member
but doesn't define it (see =A79.4.2/2 of the standard). vector<>resize()
expect a const reference as it second argument which doesn't exists.

Perhaps a feature of C++0x makes it work with 4.4.1.

--
Michael