C ++：指向int的指针的初始化

Question

Here is the sample code that I ran on Visual Studio 2010:

#include <iostream>

int main()
{
    int **p(NULL);
}

I get this error: error C2059: syntax error : 'constant'

But if I change int **p(NULL); to int **p = NULL; the above code compiles fine.

Checked this on GCC(Version:4.4.2) and both work fine. What am I missing here?

Answer 1

VC++ compiler seems confused about initializations of pointer to pointer ...

This works for example

int (**p)(NULL);

These don't

int *i;
int **p(&i);
int **o(NULL);

This works though

int (**p)(&i);
typedef int* intp;
intp *o(NULL);

etc... the pattern is initialization fails whenever two ** are present! I'd guess a bug! Someone from MSVC team might be able to confirm

Answer 2

That is either a bug in the compiler itself, or possibly you've done something and asked something else.

MSVC10 support few features from C++11, such as the following:

int **p1 = nullptr;
int **p2{}; //initialized to nullptr!

You can try any of these. Both are fine.

Answer 3

Looks like, defect with Visual studio, It works if i use c++ to compile @ http://codepad.org/ and run the following code

int main() 
{     
    int **p(NULL); 
    return 0;
} 

Same works using g++ compiler as well.

Answer 4

You get a syntax error: apparently NULL is not defined. You should include cstdlib.