c - Returning a character array from a function prints garbage values but prints fine in the function? -

#include<stdio.h> #include <string.h> char *generate(char a[],int s,int e,char r[]) {     if(s>e){         printf("%s\n ",r); //prints correct value "rempd" here         return r;     }     int i,asci[128]={0};     for(i=s;i<=e;i++)         if(asci[a[i]]==1)             break;         else             asci[a[i]]=1;     char t[i-s];     t[i-s]='\0';     for(i=i-1;i>=s;i--)         t[i-s]=a[i];     if(r==0||strlen(t)>strlen(r))         return generate(a,s+1,e,t);     else         return generate(a,s+1,e,r);  } int main() {     char a[]="prrempd";     printf("largest unique string:\n%s",generate(a,0,strlen(a)-1,null)); // prints garbage value here } 

this function used return largest unique substring within string. when character array returned, returns garbage value.

char t[i-s]; allocated on stack , gets deallocated when return generate().

if want live beyond call generate() must use heap or other allocation method.