Runtime Error "heap-buffer-overflow" when returning string

I have to admit, I had some fun debugging this code and refactoring bits of the program to derive a function that I believe meets the spirit of your project.

Regarding the error messages, I couldn't put my finger on the exact point, but I believe with the incrementing of both the "i" and "j" counters in your for loop, you probably were going out of bounds on the the string processing.

Regardless, following is a refactored version of your code with the main function performing a call to the function.

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

char * reverseWords(char * s)
{
    int n = strlen(s);
    char * res = (char *)malloc(n * sizeof(char) + 1);
    char temp[100];
    int i = 0;
    int j = 0;
    int k = 0;                              /* Work variable for adjusting counter variable "i" */

    for (j = 0; j < 100; j++)               /* Initialize the work arrays */
    {
        temp[j] = '\0';
    }

    for (j = 0; j <= n; j++)                /* Initialize the work arrays */
    {
        res[j] = '\0';
    }

    for (i = 0; i < n; i++)                 /* Just parsing through the character array passed in from the function */
    {
        for (j = 0; j < n; j++)
        {
            if (s[i + j] == ' ' || s[i + j] == '\0') break;     /* Added the test for the null terminator */
            temp[j] = s[i + j];
        }
        k = j;
        while (j > 0)
        {
            j--;
            res[i + k - j - 1] = temp[j];   /* Reversing the word that was found */
        }
        for (j = 0; j < 100; j++)
        {
            temp[j] = '\0';                 /* As a bit of caution, the work array is reinitialized */
        }

        i = i + k;                          /* Used to adjust the counter variable and also set the location */
        res[i] = s[i];                      /* This should store either a space or the null terminator       */
    }

    return res;
}

int main()
{
    char sentence[200];

    strcpy(sentence, reverseWords("Hello there my love - how are you?"));

    printf("%s\n", sentence);

    return 0;
}

Some points to note.

• In the function, the character array referenced in the function call is used directly for the character and space testing, and then the reversed word(s) are copied into the work array.
• Testing for the null terminator is also included when coming to the end of a word.
• Using an abundance of caution, once the temporary character array had been parsed for copying the reversed word into the sentence array, it is reinitialized.

With that, following is the terminal output from the program test.

@Vera:~/C_Programs/Console/ReverseWord/bin/Release$ ./ReverseWord 
olleH ereht ym evol - woh era ?uoy

Give that a try to see if this meets the spirit of your project.