Seg Fault when allocating memory and setting values to 3D array

Question

I want to create an array of 26 word arrays (to sort my lists of words by first letter) so I believe I allocated memory accordingly but when I try a test run and attempt to set a random word, "hi", to each spot which must have a word, it only works for the first 5 letters then returns a set fault. Pardon my code or description, I'm quite the beginner. HELP

Note: both my parameters are defined in external functions, wordArray is the array of words in a given text file, numWordsPerLetter is an integer array which holds the number of words that start with each letter of the alphabet.

char*** create_alphabetical_array(char** wordArray, int* numWordsPerLetter){

  char*** alphabeticalArrays;
  int i, j;

  alphabeticalArrays = malloc(sizeof(char**)*26);
  for (i = 0; i < 26; i++){
    printf("%d\n", numWordsPerLetter[i]+1);
    alphabeticalArrays[i] = malloc(sizeof(char*)*numWordsPerLetter[i]+1);
  }

  for (i = 0; i < 26; i++){
    for (j = 0; j < (numWordsPerLetter[i]+1); j++){
      printf("%d %d %d\n", i, j, numWordsPerLetter[i]+1); /* using to help debug */
      strcpy(alphabeticalArrays[i][j], "hi");
    }
  }

  return (alphabeticalArrays);
}

Answer 1

At least these 2 errors:

Wrong element size and wrong n . alphabeticalArrays[i] is a char ** , so sizeof(int) is amiss. element_size * numWordsPerLetter[i]+1 should be element_size * (numWordsPerLetter[i]+1)

Better to use p = malloc(sizeof *p * n) , then p = malloc(sizeof *(type-of p) * n) . Easier to code right, review and maintain.

// alphabeticalArrays[i] = malloc(sizeof(int)*numWordsPerLetter[i]+1);
alphabeticalArrays[i] = malloc(sizeof alphabeticalArrays[i][0] * (numWordsPerLetter[i]+1));
//                             ^---Element size--------------^   ^-------------N--------^    

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strcpy(alphabeticalArrays[i][j], "hi"); fails because alphabeticalArrays[i][j] is not assigned a pointer to allocated memory for the string "hi" . @Zelnes

alphabeticalArrays[i][j] = malloc(strlen("hi") + 1);

Alternative: research strdup() .

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Robust code would also check if the allocations succeeded.

p = malloc(n);
if (p == NULL) Handle_Failure();