I started studying C++ at university 2 months ago, and I'm trying to figure out how to pass a dynamic 2d array (pointer to pointer) to a function as an input parameter. I have this dynamic 2d array:

我在2个月前开始在大学学习C ++,我试图找出如何将动态2d数组(指针指针)作为输入参数传递给函数。我有这个动态的2d数组:

int **p;
p = new int*[R];
for(i=0; i<R; i++)
    p[i] = new int[C];

Now I want to pass this pointer p to a function as an input parameter, using const. I mean that I want the function not to be able to modify the elements of the matrix.

现在我想使用const将此指针p作为输入参数传递给函数。我的意思是我希望函数不能修改矩阵的元素。

I tried like that:

我试过这样的:

void func(const int **p) {
}

But i get this error:

但我得到这个错误:

main.cpp:19:11: error: invalid conversion from 'int**' to 'const int**' [-fpermissive]

main.cpp:19:11:错误:从'int **'到'const int **'的无效转换[-fpermissive]

main.cpp:9:6: error: initializing argument 1 of 'void func(const int**)' [-fpermissive]

main.cpp:9:6:错误:初始化'void func(const int **)'的参数1 [-fpermissive]

I tryied using typedef and it works, but it's not constant. If i do like that:

我尝试使用typedef并且它可以工作,但它不是恒定的。如果我喜欢这样:

typedef int** abc;

void func(const abc p);

main() {
abc p;
...
func(p);
}

The source compiles but function 'func' is able to modify values of "p matrix"; I want p to be an input parameter, it has to be read-only!

源编译但函数'func'能够修改“p matrix”的值;我希望p是一个输入参数,它必须是只读的!

Please, how can I pass a pointer-to-pointer to a function flagging the elements as read-only?

请问,如何将指向指针的指针传递给将元素标记为只读的函数?

Thank you in advance for you help and sorry for my bad english.

提前谢谢你的帮助,抱歉我的英语不好。

3 个解决方案

const char **cpp;
char *p;
const char c = 'A';

cpp = &p;       // constraint violation
*cpp = &c;      // valid
*p = 0;         // valid

void func(const int * const *p) {
}

typedef const int *cint_ptr_t  ;

void func(const cint_ptr_t  *p) {
}