Find an replace multiple word in a string

Hi Experts,

I have a string replacing function that needs to find and replace multiple words in a string.
I use the following function and it seems to be fine sometimes, but at times it is core dumping.  I can't seemed to understand why.  The memory allocation seems to be fine.  It core dumps little after calling this function.

For example, I want to replace all the %s with "one" in the following functions.  It is initially plan to be used with sprintf, but I don't know the number of % appear in the string so I decided do replace this using the function.

string1 = "This is string %. Plus this % too"
string2 = "This another %s is different"

bool replace_multi_words(const char *str, const char *orig, const char *rep, char* buffer)
{
    char *p = NULL;
    unsigned count = 0;
    unsigned offset = 0;
    int len = 0;
    int needed = 0;
    char *temp = malloc(strlen(str)+ 2*strlen(rep)+1);
    needed = strlen(str)+ 2*strlen(rep)+1;
    strlcpy(temp, str, strlen(str) + 1);

    while ((p = strstr(temp + offset, orig))) {
        offset = p - temp;
        strlcpy(buffer, temp, offset+1);
        buffer[offset] = '\0';
        len = strlen(rep) + strlen(p + strlen(orig)) + 1;
        snprintf(buffer + offset, len, "%s%s", rep, p + strlen(orig));
        offset += strlen(rep);
        strlcpy(temp, buffer, strlen(buffer)+1);
        count++;
    }
    free(temp);
    return count ? true : false;
}

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It is called by the following code... where id is an int like 123 and which is changed to a string "123"

replace_multi_words(pattern, "%s", itoa(id, strid, 10), buffer );

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