Error when realloc in c (exception trown (ucrtbased.dll))

Question

the function get a sentnce and need to replace between the 'n' first words. when it's come to the first realloc the program stop and the error shown up. I try a lot of combination of sentences, the new memmory i ask for is bigger then the exists memory.

my function:

void Reverse(char **sentence, int n)
{
    int m;
    char *temp;
    for (m = 0; m < n; m++, n--)
    {
        temp = (char*)malloc(strlen(sentence[m]) * sizeof(char));
        temp = sentence[m];
        sentence[m] = (char*)realloc(sentence[m], strlen(sentence[n]) * sizeof(char));
        sentence[m] = sentence[n];
        sentence[n] = (char*)realloc(sentence[n], strlen(temp) * sizeof(char));
        sentence[n] = temp;
        free(temp);
        printf("%s ", sentence[m]);
    }
}

Error

Answer 1

Take a closer look at these two lines:

temp = (char*)malloc(strlen(sentence[m]) * sizeof(char));
temp = sentence[m];

In the first you allocate memory and make temp point to that memory. In the next line you reassign temp to point somewhere else.

You do this for your reallocations as well.

Also note that by doing e.g.

sentence[m] = sentence[n];

you copy a pointer and not the contents of the memory the pointer is pointing to. It is a shallow copy. If you fix this to copy the actual contents (and have a deep copy) then you must remember that strings in C are terminated by an extra character not counted by strlen. For example the string "hello" is actually six characters long with the terminator. You must allocate space for this terminator as well.