Compiler Warning (level 4) C4218

nonstandard extension used: must specify at least a storage class or a type

With the default Microsoft extensions (/Ze), you can declare a variable without specifying a type or storage class. The default type is int.

Example

// C4218.c
// compile with: /W4
i;  // C4218

int main()
{
}

Such declarations are invalid under ANSI compatibility (/Za).