使用另一个指针C指向地址的指针

Question

I've got a function which receives a pointer to a string. Now I want to duplicate this pointer, so I could run on the string with one pointer, and have another pointer which saves the beginning of the string. I hope my question is clear, I don't want to create a pointer to the pointer (which points to where the first pointer points and changes with it), I want a pointer which will point to the address of which the first pointer points.

I tried many different ways but none of them worked, this is my latest try, I keep getting "initialization makes pointer from integer without a cast"

int move_chars (char *str, int start, int end, int dist){
    int strsize = end - start + 1;
    char *p =  *str;

Answer 1

Since p is of type char * and str is also of type char * , you just need to do:

char *p = str;

To make p point to the same memory location as str .

Your code:

char *p = *str;

Attempts to copy into p the value of the first char at the memory location that str points to, and since p is expecting another memory location and not a char , you get an error.

Your error says that "initialization makes pointer from integer without a cast". This is telling you what's happening: The compiler thinks you are manually pointing p to a specific memory location, using the value of the char *str returns as an integer. This is technically doable, but you are required to manually cast the integer into a pointer, just so it's clear you're doing what you intended, and it's not a bug like in your case.

Answer 2

Use

char *p =  str;

to declare a pointer to a char and initialise it with the value of another char pointer.

Answer 3

char *p = str

这将声明一个指向字符的指针，并使p指向str指向的内存位置