Do I need to initialize the values of a structure before I use them?

Question

I need to create a dynamic array of a struct wordStruct that holds a string and the number of times it occurs in a text file:

typedef struct wordStruct{
  char word[50];
  int count = 0;
}wordStruct;

I will get the number I need from reading the number of words in the file, let's call it wordCount.

struct wordStruct *wordList;
wordList = (wordStruct *)malloc(wordCount * sizeof(wordStruct));

Is this the correct way to allocate the memory for struct array? Would calloc() be a better option?

int wordListIndex = 0;
char[50] inWord; // No word will be more than 49 characters + null terminator
for (i = 0; i < wordCount; i++){
  fscanf(data, "%s", inWord);
  for (j = 0; j < wordCount; j++){
    if (strcmp(wordList[j].word, inWord) == 0){
      wordList[j].count++;
      break;
    }
  }
  if (j == wordCount){
  strcpy(wordList[wordListIndex].word, inWord)
  wordListIndex++;
  }

I know that this probably isn't the most efficient code, but do I have the right idea? Can I use the strcmp() method even though there may not be any data in those array locations? I'm new to structs and I'm not sure what I can and cannot do.

Thanks.

Answer 1

If you use malloc, you need to initialize the array (e.g., using memset). If you use calloc, the array is initialized to 0 for you.

Once the array is initialized, you can use strcmp on it, because setting it to 0 makes all the words be zero-length (empty) strings. Before initializing it, you must not use strcmp.

(I'm assuming the weird char[50] varname instead of char varname[50] are typos in your SO question, else this wouldn't compile. I'm also ignoring the buffer overflow in fscanf and strcpy… well, technically, I guess I'm not. And the lack of error handling.)