Ytukyg

I have been trying to get the following to work:
My goal is to use pointers in main() to access elements created in a method().

// takes in address of pointer

int method(char** input) {

    char *buffer = malloc(sizeof(char)*10);



    buffer[0] = 0x12;

    buffer[1] = 0x34;

    buffer[2] = 0xab; 



    *input = & buffer;



    printf("%xn", *buffer); // this prints 0x12

    printf("%xn", &buffer); // this prints address of buffer example: 0x7fffbd98bf78

    printf("%xn", *input); // this prints address of buffer



    return 0;

}



int main(){



    char *ptr;

    method(&ptr);



    printf(%pn", ptr); // this prints address of buffer 



    //this does not seem to print out buffer[0]

    printf(%xn", *ptr);



}   

I want to print each element of buffer values, as created by the method() by using ptr. Any suggestions on how I can go about doing this?

I am not sure if I am misunderstanding something, but I thought ptr points to address of buffer. Thus, dereferencing would give me buffer[0]?

Thank you.

This a fixed & commented version of your code. Ask in the comments if there is smth. you don't understand.

#include <stdio.h>

#include <stdlib.h>



// takes in address of pointer



//Hex: 0xab is larger than the max value of a signed char.

//Most comilers default to signed char if you don't specify unsigned.

//So you need to use unsigned for the values you chose



int method(unsigned char** input) { //<<< changed

    unsigned char *buffer = malloc(sizeof(char)*10);



    //Check for malloc success  <<< added

    if(!buffer)

        exit(EXIT_FAILURE);



    buffer[0] = 0x12;

    buffer[1] = 0x34;

    buffer[2] = 0xab;

//I recommend not to mix array notation and pointer notation on the same object.

//Alternatively, you could write:



*buffer = 0x12;

*(buffer + 1) = 0x34;

*(buffer + 2) = 0xab;



    //buffer already contains the address of your "array".

    //You don't want the address of that address

    *input = buffer;  //<<< changed (removed &)



    printf("%xn", *buffer); // this prints 0x12

    //Not casting &buffer will likely work (with compiler warnings

    //But it is better to conform. Either use (char *) or (void *)

     //<<< added the cast for printf()

    printf("%pn", (char *)&buffer); // this prints address of buffer example: 0x7fffbd98bf78

    printf("%pn", *input); // this prints address of buffer



    return 0;

}



int main(){

    unsigned char *ptr;

    method(&ptr);



    printf("%pn", ptr); // this prints address of buffer



    //this does not seem to print out buffer[0]

    for(int i = 0; i < 3; i++){

       //<<< changed to obtain content of buffer via ptr for loop.

        unsigned char buf_elem = *(ptr + i);

        printf("buffer[%d] in hex: %xt in decimal: %dn", i, buf_elem, buf_elem);

}



// Don't forget to free the memory.  //<<< changed

free(ptr);

}