strdup() is causing memory leaks everytime it's used in readLine() (bc of its auto malloc) bc Im not freeing/deallocating the memory right.

I've tried to get the adress of the word and many other methods for hours now but with no progress.

I'm doing a calloc bc I'll be storing an undetermined #of words.

This has been hardcoded (only 3 words) as to show the working example. If I get a huge amount of words in the file, the memory leak will be too important.

Text: JOHN VELMA ZORRO

#include "stdio.h"
#include <stdlib.h>
#include <string.h>

struct link {
    char *word;
    struct link *next;
};

void readLine(FILE *file, char **words) {
   int i = 0;
   char ligne[80];
   while (fgets(ligne, 80, file)){
      char *word = strtok(ligne, " ,.-\n");
      while (word != NULL) {
         words[(i)  ] = strdup(word);         //<<<<<<<<<<<<<<<<<<<<<<<<<<<     
         word = strtok(NULL, " ,.-\n");
      }
   }
   fclose(file);
}

int main(int argc, char *argv[]) {
   FILE *file = fopen(argv[1], "r");
   char **words = calloc(3, 30 * sizeof(char *)   1);
   readLine(file, words);
   struct link *head = malloc(sizeof(struct link));
   struct link *ptrr = head;
   head->word = words[0];
   head->next = NULL;
   for (int i = 1; i < 4;   i) {
      struct link *ptr, *temp;
      if (words[i] != 0) {
         ptr = head;
         temp = malloc(sizeof(struct link));
         temp->word = words[i];
         temp->next = NULL;
         while (ptr->next != NULL)
            ptr = ptr->next;
         ptr->next = temp;
      }
   }
   int a = 0;
   while (ptrr != NULL) {
      printf("Noeud#%d ->%s\n", a, ptrr->word);
      ptrr = ptrr->next;
      a  ;
   }

//////freeing **words 

 struct link *tmpp;
   while (head != NULL) {
      tmpp = head;
      head = head->next;
      free(tmpp);
   }
   for (int i = 0; i < 4;   i) {
      free(words[i]);
   }
   free(words);
   return 0;
}

CodePudding user response：

no , strdup is not causing a memory leak, you are by not freeing the memory it allocates. I note that you dont free any of your memory (the calloc and mallocs you do explictly)

strdup is this

 char *strdup(const char*s){
       int len = strlen(s)   1;
       char * res = malloc(len);
       if(res != NULL)
          strcpy(res, s);
       return res
 }

there is no magic, its just a nice utility function that encapsulates a common set of operations.

You have to free the memory it returns, just like all the other allocations

CodePudding user response：

THe reason you leak with a bigger file is this

You read the entire file into words (in readline). Note that you only reserve enough spaces for 30 words, so thats a potential error

   while (fgets(ligne, 80, file)) {
        char* word = strtok(ligne, " ,.-\n");
        while (word != NULL) {
            words[(i)  ] = _strdup(word);           
            word = strtok(NULL, " ,.-\n");
        }
    }

so lets say there are 15 words you strdup 15 times

Then you build a list

for (int i = 1; i < 4;   i) {  <<<=======
    struct link* ptr, * temp;
    if (words[i] != 0) {
        ptr = head;
        temp = malloc(sizeof(struct link));
        temp->word = words[i];
        temp->next = NULL;
        while (ptr->next != NULL)
            ptr = ptr->next;
        ptr->next = temp;
    }
}

but you only take the first 4 words.

Then when you free you only free those 4

struct link* tmpp;
while (head != NULL) {
    tmpp = head;
    head = head->next;
    free(tmpp);
}
for (int i = 0; i < 4;   i) { <<<<=============
    free(words[i]);
}
free(words);

the other 11 are leaked