c++ - 为什么不能将 char** 隐式转换为 const char **

Answer 1

because if it was allowed then you could inadvertently change something that was declared const.

here's a concrete abuse example, if the rules allowed this:

char const* s = "a literal, very const";

bar(const char** pp )
{
    *pp = s;
}

foo(char** arr)
{
  bar(arr);
  char* unconsted_s = *arr;
  unconsted_s[0] = 'X';
}

This is also a FAQ. It’s often a good idea to check the FAQ (or just google) before asking.

Answer 2

It can lead to similar scenario if its allowed.

void foo(int** arr)
{
    /*Can freely modify value at location pointed by a*/
   **arr = 6;
}


int main()
{
 /*Pointer to constant*/
 int i = 5;

 const int* a =&a;

 /*Not a pointer to constant*/
 int** aa= &a;

 foo(aa);

return 0;
}