c++ - My C program is crashing when I call a method from a class instance here is the code -

here class using.

#include<stdio.h> #include <string.h> class ende{      private:         int *k;         char *temp;      public:          char * encryptstring(char *str);                                  char * decryptstring(char *str);                 ende(int *key);};  ende::ende(int *key){      k=key; }  char * ende::encryptstring(char *str){      int t=2;     t=(int)k[1]*(int)2;     (int i=0;i<strlen(str);i++){         temp[i]=str[i]+k[0]-k[2]+2-k[1]+k[3]+t;            }     char alp=k[0]*57;     (int y=strlen(str);y<strlen(str)+9;y++){    //--*         temp[y]=alp+y;                  //--*     }     temp[(strlen(str)+9)]='\0';     //--*     return temp;  }  char * ende::decryptstring(char *str){      int t=2;     t=k[1]*2;      (int i=0;i<strlen(str);i++){          temp[i]=str[i]-t-k[3]+k[1]-2+k[2]-k[0];        }          temp[(strlen(str)-9)]='\0';     return temp;  } 

and here main program.

#include <stdio.h> #include "ende.h"  int main(void){      char *enc;      char op;      printf("\ne encrypt , d decrypt");      int opi[4]={1,2,9,1};         ende en(opi);      strcpy(enc,en.encryptstring("it c's lounge!! "));      printf("encrypted :  %s",enc);      return 0; } 

something wrong en.encryptstring function

when run program stops working giving error , on removing strcpy(enc,en.encryptstring("it c's lounge!! ")); runs. want problem resolved.

 char *enc;     strcpy(enc,en.encryptstring("it c's lounge!! ")); 

you don't provide space copy - enc doesn't point anywhere.