Another memory problem

Ok so occasionally I get a problem and I get a segfault error, and when I check it was with valgrind I get complain how when I strtok in the assignTemps(string, circuit) function, that string is do invalid reads of 1 byte. I've been looking over the code but I can't find anything wrong. Can someone help me? Thanks.

Code:

---

void getTemperature(Circuit* circuit, char* flp, char* ptrace)
{
    int osize = 0;
    int size = 0;
    char* string = 0;
    char* overflow = 0;

    int status;
    int fd[2];
    int pid;
    int chars_read;
    char buffer[BUFFER];

    pipe(fd);

    if((pid = fork()) < 0)
    {
        perror("fork");
        exit(-1);
    }

    else if(pid == 0)
    {//child
        close(fd[0]);
        dup2(fd[1], STDOUT_FILENO);

        execl(hotspotDir, hotspotDir, "-c", "hotspot.config", "-f", flp, "-p", ptrace, (char*)0);
        perror("EXEC!!!!!!!!!!!");
        exit(-1);
    }
    else
    {//parent
        pid = wait(&status);
        close(fd[1]);

        chars_read = read(fd[0], buffer, 20);

        while((chars_read = read(fd[0], buffer, BUFFER-1)) > 0)
        {
              buffer[chars_read] = '\0';
             
              size = (int)rindex(buffer, '\n') - (int)buffer;
              if(overflow == 0)
              {   
                string = malloc(size+1);
                string = strncpy(string, buffer, size);
                size = chars_read - size;
                if(size != 0)
                {
                    overflow = malloc(size+1);
                    overflow = strncpy(overflow, rindex(buffer, '\n') + 1, size);
                }
                else
                    overflow = 0;
                   
                osize = strlen(overflow);
              }
              else
              {
                osize = strlen(overflow);
                overflow = realloc(overflow, osize + size+1);
                overflow = strncat(overflow, buffer, size);
                string = overflow;
                overflow = malloc(chars_read - size+1);
                overflow = strncpy(overflow, buffer + size + 1, chars_read - size);
              }
              assignTemps(string, circuit);

        }
    }

}

---

rindex returns a pointer, which may be NULL

So this makes no sense whatsoever
> size = (int)rindex(buffer, '\n') - (int)buffer;


> chars_read = read(fd[0], buffer, 20);
Why do you junk the first 20 chars?

>rindex returns a pointer, which may be NULL

>So this makes no sense whatsoever
>> size = (int)rindex(buffer, '\n') - (int)buffer;

buffer always has a newline character so i don't have to worry about that.
That line pretty much tells me how big the line read in is.


>> chars_read = read(fd[0], buffer, 20);
>Why do you junk the first 20 chars?
This is just header information that I don't care about.

The weird thing is what that code does works most of the time.