static variable initialization problem

[danicpp]

When I try to initialize static variable from within the constructor the compiler exits and return exit status 1,

Can't we initialize static variables from constructors?

#include <iostream>
#include <string.h>
#include <iomanip>

using namespace std;

class nonsta{
	
	public:
		int a;
		int b;
		
		nonsta();
		
		~nonsta();
	
};

nonsta::nonsta(){
	
	cout << "nonsta constructor called";
	a = 5;
	b = 10;
	
}//---------constructor

nonsta::~nonsta(){
	
	cout << "nonsta destructor called";
	
}//--------destructor

class statc{
	
	public:
		static int asta;
		int bnsta;
		
		statc();
		
		~statc();
	
};

statc::statc(){
	
	cout << "statc constructor called";
//	asta = 15;
	bnsta = 20;
	
}//-------constructor

statc::~statc(){
	
	cout << "statc destructor called";
	
}//-------destructor

int main(){
	
	
	
}//--------main() 

When I out comment line 48 then compiler give following error:

C:\Users\Dani\AppData\Local\Temp\ccx4c49w.o temp.cpp:(.text+0x92): undefined reference to `statc::asta'

E:\Education\cpp\temp\collect2.exe [Error] ld returned 1 exit status

[kbw]

Can't we initialize static variables from constructors?

Yes and no.

Static member data will exist before the first instance of a class is created. So there must be a way to initize it seperately, and that's in its definition.

struct A
{
    A();
    static int s_a;
};

int A::s_a = 3;

But a constructor should be able to set the value.

A::A()
{
    ++s_a;
}

[danicpp]

Thankyou kbw, I got it constructor could do with static member too but that static member must be initialized before the constructor