Bad permissions for mapped region at address

Question

I am currently working on CS50x problem set 5, Speller. Using valgrind, i get the following error:

==395== Memcheck, a memory error detector
==395== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==395== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==395== Command: ./speller texts/cat.txt
==395== 
==395== 
==395== Process terminating with default action of signal 11 (SIGSEGV)
==395==  Bad permissions for mapped region at address 0x601DE8
==395==    at 0x401155: add_Node (dictionary.c:75)
==395==    by 0x401239: load (dictionary.c:107)
==395==    by 0x400944: main (speller.c:40)
==395== 
==395== HEAP SUMMARY:
==395==     in use at exit: 5,328,336 bytes in 95,140 blocks
==395==   total heap usage: 95,141 allocs, 1 frees, 5,332,432 bytes allocated
==395== 
==395== 552 bytes in 1 blocks are still reachable in loss record 1 of 2
==395==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==395==    by 0x5258E49: __fopen_internal (iofopen.c:65)
==395==    by 0x5258E49: fopen@@GLIBC_2.2.5 (iofopen.c:89)
==395==    by 0x4011BE: load (dictionary.c:88)
==395==    by 0x400944: main (speller.c:40)
==395== 
==395== 5,327,784 bytes in 95,139 blocks are still reachable in loss record 2 of 2
==395==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==395==    by 0x401118: add_Node (dictionary.c:69)
==395==    by 0x401239: load (dictionary.c:107)
==395==    by 0x400944: main (speller.c:40)
==395== 
==395== LEAK SUMMARY:
==395==    definitely lost: 0 bytes in 0 blocks
==395==    indirectly lost: 0 bytes in 0 blocks
==395==      possibly lost: 0 bytes in 0 blocks
==395==    still reachable: 5,328,336 bytes in 95,140 blocks
==395==         suppressed: 0 bytes in 0 blocks
==395== 
==395== For counts of detected and suppressed errors, rerun with: -v
==395== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
Segmentation fault

This is my code for the functions load and add_Node:

// Loads dictionary into memory, returning true if successful else false
bool load(const char *dictionary)
{
    FILE *file = fopen(dictionary, "r");

    if (file == NULL)
    {
        return false;
    }

    // Set pointers in table to NULL
    for (int i = 0; i < N; i++)
    {
        table[i] = NULL;
    }
    
    char word[LENGTH + 1];  //to hold a word from dictionary
    
    while (fgets(word, LENGTH + 1, file) != NULL)
    {
        int row = hash(word);   // to determine where to store the word

        add_Node(row, word);
    }
    
    fclose(file);

    return true;
}

// Adds new node to a list in dictionary
void add_Node(int row, char word[LENGTH + 1])
{
    node *newNode = malloc(sizeof(node));
    strcpy(newNode->word, word);
    
    if (table[row] == NULL)  //if single linked list is empty
    {
        table[row] = newNode;
    }
    else
    {
        node *tmpHead = table[row];   
        table[row] = newNode;
        newNode->next = tmpHead;
    }
}

Line 89 corresponds to:

add_Node(row, word);

Line 105 corresponds to "table[row] = newNode;" in:

if (table[row] == NULL)  //if single linked list is empty
        {
            table[row] = newNode;
        }

table is a global variable, an array of pointers of type node. I have already verified that row is for sure within the bounds of the array, table. I don't know how to fix this issue. What could the problem be?

Answer 1

First off let use change while (fgets(word, LENGTH + 1, file) != NULL) to while(fscanf(file, "%s", word) != EOF) since you are not reading "\n".

Your add_Node function is missing some line and need some changes:

Old:

// Adds new node to a list in dictionary
void add_Node(int row, char word[LENGTH + 1])
{
    node *newNode = malloc(sizeof(node));
    strcpy(newNode->word, word);
    
    if (table[row] == NULL)  //if single linked list is empty
    {
        table[row] = newNode;
    }
    else
    {
        node *tmpHead = table[row];   
        table[row] = newNode;
        newNode->next = tmpHead;
    }
}

New:

// Adds new node to a list in dictionary

void add_Node(int row, char word[LENGTH + 1])
{
    node *newNode = malloc(sizeof(node));
    //Test if the node is not empty
    if(newNode == NULL){
        return 1;
    }

    strcpy(newNode->word, word);
    newNode->next = NULL;
    
    if (table[row] == NULL)  //if single linked list is empty
    {
        table[row] = newNode;
    }
    else
    {   //Set the newNode to table at row and make table[row]
        //equal to newNode to overwrite the current address at table[row]. 
        //No need for tmp as we are not swapping things.
        newNode -> next = table[row];
        table[row] = newNode;
    }
}

This should solve your valgrind issue. Also you don't need a tmp node as that is not required. I am not sure if you hash function works well or not, but I assume that is fine. Final thing, make to fclose(file) at the end of the load function as that would a "reachable" memory leak according to valgrind.