pointers - c - realloc() on tokenized array: signal SIGABRT error -


on line 56, i'm trying resize array:

tokenarray = (char**) realloc(tokenarray, toksize * (sizeof(char)));

i error:

(11972,0x7fff7ca4f300) malloc: * error object 0x100105598: incorrect checksum freed object - object modified after being freed. * set breakpoint in malloc_error_break debug

this programming assignment class, have been instructed dynamically allocated arrays, , expand needed. have searched extensively thread on same isn't advanced me understand, no luck yet... can help. thanks! here code:

#include <stdio.h> #include <stdlib.h> #include <string.h>  #define max_row_size 81  void strinput(char str[], int numelem);   int main(int argc, const char * argv[]) {     printf("enter string of number of integers separated spaces or tabs.\n");     printf("maximum string length 80 characters.\n");     printf("enter empty string conclude input.\n");       int arrsize = 10, toksize = 10, = 0, j = 0;      char** inputarray = malloc(arrsize * (sizeof(char)));     char** tokenarray = malloc(toksize * (sizeof(char)));       {         inputarray[i] = malloc(max_row_size * sizeof(int));          strinput(inputarray[i], arrsize);          if ((inputarray[i][0] != '\0') && (i == (arrsize - 1)))         {             arrsize = arrsize * 2;             inputarray = (char**) realloc(inputarray, arrsize * (sizeof(char)));         }          while (inputarray[i][j] != '\0')         {             printf("%c", inputarray[i][j]);             j++;         }         j = 0;          i++;     } while (inputarray[i-1][0] != '\0');      = 0;      while (inputarray[i][0] != '\0')     {          if ((tokenarray[j] = strtok(inputarray[i], " \t")))             j++;         while ((tokenarray[j] = strtok(null, " \t")))         {             if (j == (toksize - 1))             {                 toksize = 2 * toksize;   //this line error                 tokenarray = (char**) realloc(tokenarray, toksize * (sizeof(char)));             }             j++;         }         i++;     }      printf("printing tokenized arrays: ");     (i = 0; < j; i++)         printf("%s ", tokenarray[i]);      free(inputarray);     free(tokenarray);      return 0; }  void strinput(char str[], int numelem) {       int j, k = 0;      j = k;      while ((str[k] = getchar()) != '\n')     {         k++;     }      if (str[k] == '\n')         str[k] = '\0'; }

1. not cast result of malloc , friends.

it's useless @ best , dangerous @ worst.

2. mind size malloc'ing.

char** inputarray = malloc(arrsize * (sizeof(char)));

this makes no sense, , accidental. rule of thumb, type malloc'ing , pointer you're pointing @ resulting storage should differ 1 indirection. i.e :

char** inputarray = malloc(arrsize * sizeof(char*)); //  ^^ double-pointer     vs     single pointer ^

better rule of thumb yet, let compiler figure out. sizeof can deduce type should measure expression.

char **inputarray = malloc(arrsize * sizeof(*inputarray));

this works because operand of sizeof unevaluated context. pointer won't dereferenced, type deduced.
side note : sizeof's parentheses not needed around expression, i've left them clarity. remove them once you're comfortable it.

3. check allocation successful.

malloc , friends return null in case of trouble. should check that.

4. fix realloc

inputarray = realloc(inputarray, /*...*/);

this wrong. mentioned above, if realloc fails, return null and nothing else. means inputarray still points @ previous storage. is, until trump pointer null realloc returned, , leak said storage. oops.

always store, check, , then assign result of realloc.

char **inputarray_ = realloc(inputarray, /*...*/); if(!inputarray_) {     /* allocation failure, handle , break out */ } inputarray = inputarray_;

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