C在函数中更改指针

Question

I want to write a function that processes a string that looks like this:

|1,2,3,4|(1->2),(2->3),(3->1)|

The result should be a breaking down of the string into these strings:

• 1
• 2
• 3
• 4
• (1->2)
• (2->3)
• (3->2)

This is my code:

int processPart(char*** dest, char* from) //Processes a half at a time
{
    int len = 0;
    char* cutout = strtok(from, ",");
    while(cutout)
    {
        (*dest) = (char**)realloc(dest, (len + 1) * sizeof(char*)); <<<<<<<
        (*dest)[len] = (char*)calloc(strlen(cutout) + 1, sizeof(char));
        memcpy((*dest)[len], cutout, strlen(cutout));
        cutout = strtok(NULL, ",");
        len++;
    }
    return len;
}

void processInput(char*** vertices, char*** edges, char* input, int* sizev, int* sizee)
{
    int vlen = 0, elen = 0;
    char* string = input + 1;
    char* raw_vertices;
    char* raw_edges;
    string[strlen(string)] = '\0';
    raw_vertices = strtok(string, "|");
    raw_edges = strtok(NULL, "|");
    *sizev = processPart(vertices, raw_vertices); //First the vertices
    *sizee = processPart(edges, raw_edges); //Then the edges
}

int main()
{
    char* in = stInput(); //input function
    char** c = NULL, **b = NULL;
    int a, d, i;
    processInput(&c, &b, in, &a, &d);
    for(i = 0; i < a; i++)
    {
        printf("%s\n", c[i]);
    }
    printf("++++++++++++++++");
    for(i = 0; i < d; i++)
    {
        printf("%s\n", b[i]);
    }
    return 0;
}

However, I get a corruption of the heap at the line marked by <<<<<<<

Anyone knows what my mistake is?

Answer 1

In the erroneous line

        (*dest) = (char**)realloc(dest, (len + 1) * sizeof(char*));

a * is missing before the dest argument. You could have spotted this easier if you hadn't cluttered the expression with the useless cast. I'd write

        *dest = realloc(*dest, (len + 1) * sizeof**dest);

- that way we can see better the matching of first argument and left operand of the assignment.