malloc(): memory corruption on string concatenation - c

Question

Hello i am doing a project where i have to implement a hashTable that stores words based on a hash function. On a stress test i get malloc(): memory corruption
The initial declaration of the hashTable
hashTable = (char**)malloc(hashSize[0] * sizeof(char*));
This is the function i wrote to add word to hashTable of hashSize:
void addWord(char** hashTable, unsigned int hashSize, const char* word) {
int bucketIndex = hash(word, hashSize);
//printf("Word to add = %s, bucket = %d, hashTable size = %d\n", word, bucketIndex, hashSize);
if(hashTable[bucketIndex] == NULL) {
hashTable[bucketIndex] = (char*)malloc(strlen(word) * sizeof(char));
strcpy(hashTable[bucketIndex], word);
return;
}
/* checks for duplicats */
int exists = 0;
char* heyStack = (char*)malloc(strlen(hashTable[bucketIndex]));
memcpy(heyStack, hashTable[bucketIndex], strlen(hashTable[bucketIndex]));
char* token = strtok(heyStack, " ");
while(token) {
if(strcmp(token, word) == 0) {
exists = 1;
break;
}
token = strtok(NULL, " ");
}
/* end check for duplicates */
if(exists == 0) {
size_t bucketSize = strlen(hashTable[bucketIndex]);
hashTable[bucketIndex] = (char*)realloc(hashTable[bucketIndex], bucketSize + strlen(word) + 2);
memcpy(hashTable[bucketIndex] + bucketSize, " ", 1);
memcpy(hashTable[bucketIndex] + bucketSize + 1, word, strlen(word) + 1);
}
}
I have a stress test that adds 20k words to the table and it always breaks on the same word (no 10k something)
Any ideas on what i am doing wrong ?
Tyvm

Answer 1

You have to terminate the "strings" before passing it to functions that deal with strings, such as strlen() and strtok().
Allocate size of the string and one more byte for terminating null-character.
Terminate the "strings" by adding null character.
Notes:
They say you shouldn't cast the result of malloc() in C.
sizeof(char) will always be 1, so you don't need to multiply with it.
Corrected code:
void addWord(char** hashTable, unsigned int hashSize, const char* word) {
int bucketIndex = hash(word, hashSize);
//printf("Word to add = %s, bucket = %d, hashTable size = %d\n", word, bucketIndex, hashSize);
if(hashTable[bucketIndex] == NULL) {
size_t wordSize = strlen(word);
hashTable[bucketIndex] = malloc(wordSize + 1); /* size +1 */
memcpy(hashTable[bucketIndex], word, wordSize + 1); /* why did you use strcpy() only in here? */
return;
}
/* checks for duplicats */
int exists = 0;
size_t dataSize = strlen(hashTable[bucketIndex]);
char* heyStack = malloc(dataSize + 1); /* size +1 */
memcpy(heyStack, hashTable[bucketIndex], dataSize + 1); /* size +1 */
char* token = strtok(heyStack, " ");
while(token) {
if(strcmp(token, word) == 0) {
exists = 1;
break;
}
token = strtok(NULL, " ");
}
/* end check for duplicates */
if(exists == 0) {
size_t bucketSize = strlen(hashTable[bucketIndex]);
size_t wordSize = strlen(word);
hashTable[bucketIndex] = realloc(hashTable[bucketIndex], bucketSize + wordSize + 2);
memcpy(hashTable[bucketIndex] + bucketSize, " ", 1);
memcpy(hashTable[bucketIndex] + bucketSize + 1, word, wordSize + 1);
}
free(heyStack); /* do free what you allocated */
}
This code will be better if you add some code to check if malloc() and realloc() are successful.