GCC关于为数组分配指针变量的警告？

Question

code snippet:

int *c[2] = {{1,2,3}, {4,5,6}};

gives warning:

warning: incompatible integer to pointer conversion initializing 'int *' with an expression of type 'int'
      [-Wint-conversion]
    int *c[2] = {{1,2,3}, {4,5,6}};
                  ^
warning: excess elements in scalar initializer
    int *c[2] = {{1,2,3}, {4,5,6}};
                    ^

I suppose array {1,2,3} would decay to pointer so the assignment be legit?

Further more, according to the warning, why does the compiler think i'm trying to assign int to int * ? instead of int array type to int * ? Thanks in advance!

Answer 1

Bracketed initializers are not arrays, and so cannot undergo decay to a pointer type. And because c is an array of int * , each initializer needs to be of that type. Nested initializers only work with actual arrays (not pointers) or structs.

What you can do however is use compound literals in the initializer which do have an array type.

int *c[2] = {(int []){1,2,3}, (int []){4,5,6}};

Answer 2

I suppose array {1,2,3} would decay to pointer so the assignment be legit?

No. {1, 2, 3} is not an array, and no decay applies to it. It is an initializer suitable for initializing an array of three or more elements of arithmetic type, but you are trying to use it to initialize a pointer. You could do something like this, instead:

static int x[] = { 1, 2, 3 };
static int y[] = { 4, 5, 6 };
int *c[] = { x, y };

Or you could use compound literals to avoid declaring variables x and y , as another answer suggests. In either of these cases, the initializer elements are arrays, and they do decay to pointers.