My understanding is that C++ allows static const members to be defined inside a class so long as it's an integer type.
Why, then, does the following code give me a linker error?
#include <algorithm>
#include <iostream>
class test
{
public:
static const int N = 10;
};
int main()
{
std::cout << test::N << "\n";
std::min(9, test::N);
}
The error I get is:
test.cpp:(.text+0x130): undefined reference to `test::N'
collect2: ld returned 1 exit status
Interestingly, if I comment out the call to std::min, the code compiles and links just fine (even though test::N is also referenced on the previous line).
Any idea as to what's going on?
My compiler is gcc 4.4 on Linux.
Best Answer
You are sort of correct. You are allowed to initialize static const integrals in the class declaration but that is not a definition.
std::min takes its parameters by const reference. If it took them by value you'd not have this problem but since you need a reference you also need a definition.
Here's chapter/verse:
See Chu's answer for a possible workaround.