Misspelling problem set: Valgrind reports 'invalid' read in unload function

Question

I've been stuck on a segmentation fault error occurring on my unload() function. Here's the relevant code:

bool unload(void)
{
    if (root != NULL)
    {
        printf("Address: %p\n", (node *)root) ;
        freemem(root) ;
    }
    return true ;
}

void freemem(node *current)
{
    // For each node, check if all children are NULL
    for (int i = 0; i<27; i++)
    {
        if (current->children[i] != NULL)
        {
            freemem(current->children[i]) ; 
        }
    }
    // If all children are pointing to NULL, free current node
    free(current) ;
    return ;
}

At if (current->children[i] != NULL) is where the segmentation fault occurs, and it occurs at the first iteration of the for loop; i.e., at i=0. Valgrind reports the following for that line.

==29979== Invalid read of size 8
==29979==    at 0x401488: freemem (dictionary.c:180)

Also, GDB shows that the address of the variable current doesn't match that of root at the point of the segmentation fault.

Any ideas what I'm doing wrong? Thank you!

Answer 1

Answered in comments. Please accept this answer to remove from unanswered question pool.

The code posted works fine when I plug it into my file. No seg faults, no memory leaks, nothing. Is it possible that you are freeing root elsewhere in the file? If you can't solve it from here, you will need to post the entire dictionary.c file, and any other files that have been changed. – Cliff B 2 days ago

You are right, @Cliff B! What happened was I had the global root node and the local current node for the load and check functions, which I freed before exiting these functions. It was the completely wrong thing to do. Code's working properly now. Thank you! – user571403 6 hours ago