Thread: Why is `rpcb_getaddr' failing?

Why is my linker warning me "C:/cygwin/home/eb/rap00/main.c:94: warning: passing arg 4 of `rpcb_getaddr' from incompatible pointer type"?


And yes, rpcb_getaddr() fails.

Code:

/*
 * The netbuf structure is used for transport-independent address storage.
 */
struct netbuf {
  unsigned int maxlen;
  unsigned int len;
  void *buf;
};




struct netbuf svcaddr;


  struct netconfig *nconf;
  char host[255] ; /* The remote host name */


  svcaddr.len = 0;
  svcaddr.maxlen = ADDRBUFSIZE;
  svcaddr.buf = addrbuf;


  /* Get pointer to struct netconfig for tcp transport */
  nconf = getnetconfigent("tcp");
  if (nconf == (struct netconfig *) NULL) {
    printf("getnetconfigent() failed\n");
    exit(1);
  }


  /* Get the address of remote service */
  if (!rpcb_getaddr(300456, 1, nconf, &svcaddr, host)) {
    printf("rpcb_getaddr() failed\n");
    exit(1);
  }

Well, it would seem that there is something wrong with how you are passing the fourth argument (&scvaddress) of 'rcbp_getaddr'. In more detail, it's probably something to do with the pointer type (struct netbuf*) being incompatible (with the function declaration).

I can't find any documentation for rpcb_getaddress but I find it hard to believe that you need to define one of the structures that it takes yourself.

According to this I'm doing it right:Help - AIX 6.1 Information Center


I think I'm structuring netbuf wrong.
Should I have mentioned that this is in Cygwin? Probably huh?
Perhaps the Cygwin struct is different from the IBM struct? I doubt it but it's all I have for now.

fyi - my Build Log:



-------------- Clean: Release in rap00 ---------------


Cleaned "rap00 - Release"


-------------- Build: Release in rap00 ---------------


gcc-3.exe -Wall -O2 -IC:/cygwin/usr/include/tirpc -IC:/cygwin/usr/include -c C:/cygwin/home/eb/rap00/main.c -o obj/Release/main.o
C:/cygwin/home/eb/rap00/main.c: In function `rapvar_read_name_1':
C:/cygwin/home/eb/rap00/main.c:41: warning: function returns address of local variable
C:/cygwin/home/eb/rap00/main.c: In function `main':
C:/cygwin/home/eb/rap00/main.c:95: warning: passing arg 4 of `rpcb_getaddr' from incompatible pointer type
g++-3.exe -o bin/Release/rap00.exe obj/Release/main.o C:/cygwin/lib/libtirpc.a
Output size is 113.62 KB
Process terminated with status 0 (0 minutes, 1 seconds)
0 errors, 2 warnings

OH! Here's the code:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <memory.h> /* for memset */
#include "rap.h"
#include <rpc/rpc.h>


/* Default timeout can be changed using clnt_control() */
static struct timeval TIMEOUT = { 25, 0 };


RAPVAR_READ_NAME_RESP_TYPE *rapvar_read_name_1(RAPVAR_READ_NAME_REQ_TYPE *argp, CLIENT *clnt)
{
    RAPVAR_READ_NAME_REQ_TYPE *inproc = NULL;
    RAPVAR_READ_NAME_RESP_TYPE *outproc = NULL;
    RAPVAR_READ_NAME_RESP_TYPE clnt_res;


    memset((char *)&clnt_res, 0, sizeof(clnt_res));


    if (clnt_call (clnt, 1001, (xdrproc_t) inproc, (caddr_t) argp,              /*---CRASH--- */
                   (xdrproc_t) outproc, (caddr_t) &clnt_res, TIMEOUT) != RPC_SUCCESS)
    {
        return (NULL);
        printf("clnt_call FAILED!\n");
    }
    printf("Hello world!\n");
    return (&clnt_res);
}


int main()
{
    int pstat=0;
    RAPVAR_READ_NAME_RESP_TYPE *result = NULL;
    RAPVAR_READ_NAME_REQ_TYPE request;


    CLIENT *clnt = NULL;
    clnt = clnt_create("s4c",300456,1,"tcp");
    if(clnt==NULL) printf("Client is\tNULL\n");
    if(clnt!=NULL) printf("Client is\tCREATED\n");


    CLIENT *clnt2 = NULL;
    clnt2 = clnt_create("192.168.1.2",300456,1,"tcp");
    if(clnt2==NULL) printf("Client2 is\tNULL\n");
    if(clnt2!=NULL) printf("Client is\tCREATED\n");


#define ADDRBUFSIZE 255


  CLIENT *clnt3;
  int sock = RPC_ANYSOCK;
  unsigned int sendsz=0, recvsz=0;
  struct sockaddr_in addr;
  char addrbuf[ADDRBUFSIZE];
  struct netbuf {
  unsigned int maxlen;
  unsigned int len;
  void *buf;
};


  struct netbuf svcaddr;
  struct netconfig *nconf;
  char host[255] ; /* The remote host name */


  svcaddr.len = 0;
  svcaddr.maxlen = ADDRBUFSIZE;
  svcaddr.buf = addrbuf;


  /* Get pointer to struct netconfig for tcp transport */
  nconf = getnetconfigent("tcp");
  if (nconf == (struct netconfig *) NULL) {
    printf("getnetconfigent() failed\n");
    exit(1);
  }


  /* Get the address of remote service */
  if (!rpcb_getaddr(300456, 1, nconf, &svcaddr, host)) {
    printf("rpcb_getaddr() failed\n");
    exit(1);
  }
  memcpy(&addr, svcaddr.buf, sizeof(struct sockaddr_in));


  clnt3 = (CLIENT *) clnttcp_create(&addr, 300456, 1, &sock, sendsz, recvsz);


  /* Destroy the client handle in the end */
  clnt_destroy(clnt3);


    char string [256];
    printf ("Hit [Enter] to exit (irony):");
    gets (string);


    request.head.userdef=1;
    request.var.name="name";
    request.var.type="robposdata";
    request.var.domain=1;
    request.var.number1=0;
    request.var.number2=26;			                    /*ROBTARGET_TRANSFER_TYPE */


    result = rapvar_read_name_1(&request, clnt);		/*Call the RPC function */


    if (result == (RAPVAR_READ_NAME_RESP_TYPE *) NULL)
    {
        printf("'result' is NULL\n");
        pstat = -1;
        return(0);
    }
    return 0;
}

DANG! I don't know how I missed that duplicate struct.
Problem solved.
Thanks again Tim!

Originally Posted by [email protected]

C:/cygwin/home/eb/rap00/main.c: In function `rapvar_read_name_1':
C:/cygwin/home/eb/rap00/main.c:41: warning: function returns address of local variable

This will likely be a major problem. The minute the function returns, that variable (clnt_res) goes out of scope, thus returning it's address results in undefined behavior. Never return the address of a local variable (including returning arrays). You can only return a pointer to memory that is valid after the function call is done, like memory you malloc, static locals, globals (ick) or variables in a "higher" scope (belonging to a function that directly or indirectly called this one) that you passed in.

Thanks for the heads up. I'll make it global.

Originally Posted by [email protected]

Thanks for the heads up. I'll make it global.

You pick the one alternative that I put an "ick" next to. Why? Read this: Global Variables Are Bad. I would suggest passing in a pointer to an object that you can populate:

Code:

RAPVAR_READ_NAME_RESP_TYPE *rapvar_read_name_1(RAPVAR_READ_NAME_REQ_TYPE *argp, CLIENT *clnt, RAPVAR_READ_NAME_RESP_TYPE *clnt_res)
{
    clnt_call (..., (caddr_t) clnt_res, TIMEOUT)  // note no & in front of clnt_res, it's already a pointer

    return clnt_res;  // this is safe, because the address was passed in, so it must be valid in the outer context
}
...
// in the calling context
RAPVAR_READ_NAME_RESP_TYPE clnt_res;
rapvar_read_name_1(argp, clnt, &clnt_res);