warning: in-class initialization of non-static data member is a C++11 extension [-Wc++11-extensions]

struct test{
int a=1111111;

}test;

vincentdeMacBook-Air:datasturte vincent$ g++ struct.cpp -o structpp
struct.cpp:4:6: warning: in-class initialization of non-static data member is a
      C++11 extension [-Wc++11-extensions]
int a=11111111;
     ^
1 warning generated.

struct test{
const int a=1111111;

}test;

vincentdeMacBook-Air:datasturte vincent$ g++ struct.cpp -o structpp
struct.cpp:4:12: warning: in-class initialization of non-static data member is a
      C++11 extension [-Wc++11-extensions]
const int a=11111111;
           ^
struct.cpp:29:4: error: cannot assign to non-static data member 'a' with
      const-qualified type 'const int'
q.a=10;
~~~^
struct.cpp:4:11: note: non-static data member 'a' declared const here
const int a=11111111;
~~~~~~~~~~^~~~~~~~~~
1 warning and 1 error generated.
vincentdeMacBook-Air:datasturte vincent$ g++ struct.cpp -o structpp
struct.cpp:29:4: error: cannot assign to static data member 'a' with
      const-qualified type 'const int'
q.a=10;
~~~^

struct test{

static int a=11111111;

}test;

struct.cpp:4:18: note: static data member 'a' declared const here
static const int a=11111111;
~~~~~~~~~~~~~~~~~^~~~~~~~~~
1 error generated.



vincentdeMacBook-Air:datasturte vincent$ g++ struct.cpp -o structpp
struct.cpp:4:12: error: non-const static data member must be initialized out of
      line
static int a=11111111;
           ^ ~~~~~~~~
1 error generated.

　　同样问题：http://stackoverflow.com/questions/13662441/c11-allows-in-class-initialization-of-non-static-and-non-const-members-what-c