Thread: String Reverse in C

The first char you are copying is the '\0' that terminates stringt (i.e., stringt[len] is '\0'). Then you copy all the other characters (and forget to put a '\0' at the end). So with the '\0' at the beginning, the result is interpretted as an empty string and nothing gets printed.

You also don't malloc enough space. It needs to be len + 1 to include the terminating '\0' char (which is not counted by strlen). And you need to add the '\0' after the loop.

BTW, your free() call will never happen since the return before it will tranfer control back to main. The free() needs to be in main anyway.

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
 
char *reversestring(const char *str){
    int len = strlen(str);
    char *ret = malloc(len + 1);
    int i = 0;
    for(int j = len; j-- > 0; )
        ret[i++] = str[j];
    ret[i] = '\0';
    return ret;
}
 
int main(){
    char *s = reversestring("teste");
    printf("%s\n", s);
    free(s);
}