CODEWITHSUNDEEP
c++static
h8n2
h8n2

Reputation: 679

Why can't a static member variable be defined inside main()?

class test 
{
public:
  static int i;

  int func() {
    return i;
  }
};

int main() 
{ 
  test::i = 20;
}

fails to compile with clang: error: linker command failed with exit code 1 (use -v to see invocation).

If I make the static variable inline, I can define it inside main. Or if I don't make it inline, I can define it between the class declaration and main() like so:

class test 
{
public:
  static int i;

  int func() {
    return i;
  }
};

int test::i = 20;

int main() 
{ 

}

Why does this work but the former doesn't? Also, why is an int here needed when it's already been declared as an int inside test?

Upvotes: 0

Views: 141

Answers (1)

Brian Bi
Brian Bi

Reputation: 119184

Inside a function, the statement

test::i = 20;

is an expression (not a definition). It stores the value 20 into test::i. But if test::i was never defined, you cannot store a value into it.

On the other hand, at namespace scope, when you write

int test::i = 20;

this is a definition of test::i.

Upvotes: 2

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