Issues using realloc (old size) - c

Question

I'm trying to use realloc function in C, to dynamically operate on a char array of strings (char**).
I usually get a realloc():invalid old size error after 41st cicle of the for loop and I really can't understand why.
So, thanks to everyone who will help me ^-^
[EDIT] I'm trying to make the post more clear and following your advices, as a "new active member" of this community, so thank you all!
typedef struct _WordsOfInterest { // this is in an header file containing just
char **saved; // the struct and libraries
int index;
} wordsOfInterest;
int main() {
char *token1, *token2, *save1 = NULL, file[LEN], *temp, *word, **tokenArr;
int n=0, ch,ch2, flag=0, size, init=0,position,currEdit,init2=0,tempEdit,size_arr=LEN,
oldIndex=0,totalIndex=0,*editArr,counterTok=0;
wordsOfInterest toPrint;
char **final;
toPrint.index = 0;
toPrint.saved = malloc(sizeof(char*)*LEN);
editArr = malloc(sizeof(int)*LEN);
tokenArr = malloc(sizeof(char*)*LEN);
final = malloc(sizeof(char*)*1);
// external for loop
for(...) {
tokenArr[counterTok] = token1;
// internal while loop
while(...) {
// some code here surely not involved in the issue
} else {
if(init2 == 0) {
currEdit = config(token1,token2);
toPrint.saved[toPrint.index] = token2;
toPrint.index++;
init2 = 1;
} else {
if((abs((int)strlen(token1)-(int)strlen(token2)))<=currEdit) {
if((tempEdit = config(token1,token2)) == currEdit) {
toPrint.saved[toPrint.index] = token2;
toPrint.index++;
if(toPrint.index == size_arr-1) {
size_arr = size_arr*2;
toPrint.saved = realloc(toPrint.saved, size_arr);
}
} else if((tempEdit = config(token1,token2))<currEdit) {
freeArr(toPrint, size_arr);
toPrint.saved[toPrint.index] = token2;
toPrint.index++;
currEdit = tempEdit;
}
}
}
flag = 0;
word = NULL;
temp = NULL;
freeArr(toPrint, size_arr);
}
}
editArr[counterTok] = currEdit;
init2 = 0;
totalIndex = totalIndex + toPrint.index + 1;
final = realloc(final, (sizeof(char*)*totalIndex));
uniteArr(toPrint, final, oldIndex);
oldIndex = toPrint.index;
freeArr(toPrint,size_arr);
fseek(fp2,0,SEEK_SET);
counterTok++;
}

Answer 1

You start with final uninitialized.
char **final;
change it to:
char **final = NULL;
Even if you are starting with no allocation, it needs a valid value (e.g. NULL) because if you don't initialize a local variable to NULL, it gets garbage, and realloc() will think it is reallocating a valid chunk of memory and will fail into Undefined Behaviour. This is probably your problem, but as you have eliminated a lot of code in between the declaration and the first usage of realloc, whe cannot guess what is happening here.
Anyway, if you have indeed initialized it, I cannot say, as you have hidden part of the code, unlistening the recommendation of How to create a Minimal, Reproducible Example
.
There are several reasons (mostly explained there) to provide a full but m inimal, out of the box, failing code. This allows us to test that code without having to provide (and probably solving, all or part) the neccesary code to make it run. If you only post a concept, you cannot expect from us complete, full running, and tested code, degrading strongly the quality of SO answers.
This means you have work to do before posting, not just eliminating what you think is not worth mentioning.
You need to build a sample that, with minimum code, shows the actual behaviour you see (a nonworking complete program) This means eliminating everything that is not related to the problem.
You need (and this is by far more important) to, before sending the code, to test it at your site, and see that it behaves as you see at home. There are many examples that, when eliminated the unrelated code, don't show the commented behaviour.
...and then, without touching anymore the code, send it as is. Many times we see code that has been touched before sending, and the problem dissapeared.
If we need to build a program, we will probably do it with many other mistakes, but not yours, and this desvirtuates the purpose of this forum.
Finally, sorry for the flame.... but it is necessary to make people read the rules.