Why Garbage value is getting printed???

I have written a simple RPC program for a simple increment operation on an integer using RPCGEN.

Code is getting compiled fine without any errors, when i call the client after starting the server, the method which i wrote for server is not getting called even after writing a small print statement to check whether the remote method is being called or not, i have no idea where i am going wrong

Here are the codes which i wrote

incapp_clnt.c

Code:

 
int main(int argc,char* argv[])
 {
 
     CLIENT *cl;
     int a= 9;
     int *num,*res;
     num = &a;
 
     if (argc != 2) {
         printf("Usage: firstmain hostname\n");
         exit(1);
     }
 
     cl = clnt_create(argv[1], ADDAPP, ADDAPP_V1,"tcp");
 
     if (cl == NULL) 
     {
             printf("error: could not connect to server.\n");
             return 1;
         }
 
     printf("The value of num is:%d\n",*num);
     res = add_1(num,cl);
 
     printf("Back from firsttry\n");
     if (res == NULL) {
         clnt_perror(cl,argv[1]);
         exit(1);
     }
 
     printf("After addition=%d\n",*res);
 
     return 0;
 }

incapp_svr.c

Code:

   

int* add_1_svc(int* num, struct svc_req* cli)
 {
     printf("The server is getting called"); //For checking whether server is being called or not
     int b;
     int *res;
     b = *num++;
     res = &b;
     return res;
 }

Please tell me where i am going wrong
Thanks a lot in advance

Siddarth777

You're returning the address of an local variable from add_1_svc.

Presumably *num++ is enough to increment num in the caller.

For a quick test, try changing your final printf to:

Code:

printf("After addition=%d\n",*num);

Why all the pointless layers here? You could do this I guess.

Code:

int add_1_svc(int* num, struct svc_req* cli)
 {
     printf("The server is getting called"); //For checking whether server is being called or not
     return *num += 1;
 }

What you were doing in this function before is undefined behavior: b was a local variable, a copy of the num pointee. You cannot return a pointer to the local variable. After the function ends the local variable gets destroyed and any pointers to it will dangle. My guess was that showed up as a garbage variable in the program.

Originally Posted by oogabooga

You're returning the address of an local variable from add_1_svc.

Presumably *num++ is enough to increment num in the caller.

For a quick test, try changing your final printf to:

Code:

printf("After addition=%d\n",*num);

Oops.
*num++ is NOT going to increment num in the caller. It just increments the POINTER num.
It should be ++*num.