Structures using pointers get wrong

Question

I made code of bob the builder, it's a structure, every bob the builder has name and two more integers (doesn't really matter). there are three functions

1. initialize the struct(with "bob" and 0 and 3)

2. the second function get two structures and it's needs to copy between those structures

3. the third function is to free the names(char*) of every bob.

Firstly, the second function(copy) went wrong in the debugging because it didn't copy the name(Need your help in analyzing why it happened) and secondly, the code crashed in the free function. Can someone tell me how to free names(char*) of structures?

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define LENGTH_OF_BOB 4

typedef struct bobTheBuilder
{
    char* name;
    int fixed;
    int maxFix;
}bob;

//typedef struct bobTHeBuilder bob;

void deleteBob(bob currBob);
void initBob(bob *currBob);
void copyStruct(bob* dst, bob src);
int main(void)
{
    bob currBob = {0,0,0};
    bob secondBob;
    initBob(&currBob);
    copyStruct(&secondBob, currBob);
    deleteBob(currBob);
    deleteBob(secondBob);
    system("PAUSE");    
    return 0;
}
/*
*/
void initBob(bob *currBob)
{
    char* str = (char*)calloc(LENGTH_OF_BOB, sizeof(char));
    char string[] = "bob";
    if (str)
    {
        strcat(string, "\0");
        str = string;

        currBob->name = str;
        currBob->fixed = 0;
        currBob->maxFix = 3;
    }
}
/*
*/
void deleteBob(bob currBob)
{
    free(currBob.name);
}
void copyStruct(bob* dest, bob src)
{
    dest->fixed = src.fixed;
    dest->maxFix = src.maxFix;
    dest->name = (char*)malloc(sizeof(char) *LENGTH_OF_BOB);
    strncpy(dest->name, src.name, LENGTH_OF_BOB);
}

Answer 1

In initBob you have:

char* str = (char*)calloc(LENGTH_OF_BOB, sizeof(char));
char string[] = "bob";
str = string;
currBob->name = str;

That sets currBob->name to point to a local automatic variable. Not to the dynamcically allocated buffer. The automatic variable goes out of scope when the function exits and hence is no longer valid. And of course it cannot be freed as it is not dynamically allocated memory.

I'm not really sure what you are trying to do there. Besides incorrectly setting str to point to a local variable you also have an unnecessary strcat. I'm guessing you are trying to NUL terminate the buffer. But that is unnecessary as initialising an unsized char array with a string literal already guarantees NUL termination.

With these issues in mind, the initBob function should be more like:

void initBob(bob *currBob)
{
    currBob->name = calloc(LENGTH_OF_BOB, sizeof(char));
    if (currBob->name)
    {
        strcpy(currBob->name, "bob");  
        currBob->fixed = 0;
        currBob->maxFix = 3;
    }
}