Question

assignment makes pointer from integer without a cast

Asked by: TwentyFourSeven

Hi,

Have been trying to get to grips with both C and BerkeleyDB recently, being a newbie to both.

Wrote my first callback today (below), but during compiling I get the following

 error warning: assignment makes pointer from integer without a cast

The line in question is   skey->data = edata1->val1;.

val1 is a long.

The solution is probably obvious, but I could do with an expert to help me figure it out quicker !

//CREATE CALLBACKS
int   
val1callback(DB *dbp, const DBT *key, const DBT *data, DBT *skey)
{
        Comparex        *edata1;
        edata1 = data->data;
        memset(skey, 0, sizeof(DBT));
        skey->data = edata1->val1;
        skey->size = sizeof((edata1->val1));
        return (0);
}

                                  
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:

Select allOpen in new window

This Question has been solved and asker verified All Experts Exchange premium technology solutions are available to subscription members.

Subscribe now for full access to Experts Exchange and get

Instant Access to this Solution

  • Plus...
  • 30 Day FREE access, no risk, no obligation
  • Collaborate with the world's top tech experts
  • Unlimited access to our exclusive solution database
  • Never be left without tech help again

Subscribe Now

Asked On
2009-09-20 at 14:08:28ID24747067
Topic

C Programming Language

Participating Experts
2
Points
125
Comments
9

Trusted by hundreds of thousands everyday for fast, accurate and reliable tech support.

  • "The time we save is the biggest benefit of Experts Exchange to Warner Bros. What could take multiple guys 2 hours or more each to find is accessed in around 15 minutes on Experts Exchange." Mike Kapnisakis, Warner Bros.
  • "Our team likes having a resource that is more secure than just using Google and most experts using this service really know their stuff. It's nice to look here first versus using Google." Dayna Sellner, Lockheed Martin
  • "Anytime that I've been stumped with a problem, 9 out of 10 times Experts Exchange has either the accepted solution or an open discussion of the potential solution to the problem." Kenny Red, eBay Inc.

See what Experts Exchange can do for you.

Got a question?

We've got the answer.

Experts Exchange has been collecting answers to technology questions since 1996…3 million and counting! If you have a question, chances are we already have your answer.

Screenshot of Experts Exchange Knowledgebase

Need individual assistance?

Our experts are ready to help.

If you can't find the exact answer you're looking for, ask our exclusive community of 50,000 experts. You’ll get a personalized answer from a trusted professional.

Screenshot of Experts Exchange Knowledgebase

Want to learn from the best?

Read articles from industry experts.

Thousands of free tech tips, tricks, how-to’s and tutorials are available in our peer reviewed articles section. See for yourself how smart our experts are, no login required.

Screenshot of an Article

Working on a long term project?

Store your work and research.

Save solutions to your questions, answers you’ve discovered through searching plus helpful articles in your personal knowledgebase for easy future access.

Screenshot of Experts Exchange Knowledgebase

Access the answers to your technology questions today.

Subscribe Now

30-day free trial. Register in 60 seconds.

What Makes Experts Exchange Unique?

Members of the expert community talk about why the experience at Experts Exchange is different than what you will find anywhere else.

Trusted by the world's most respected brands.

image of each brand's logo

Faithfully serving IT professionals since 1996.

Experts Exchange Logo

Try it out and discover for yourself.

Subscribe Now

30-day free trial. Register in 60 seconds.

Related Solutions

  1. (int) Integer Cast
    How do I cast to an integer in JavaScript ? var i; .. ii = (int) i*0.5 .. I don't want it to be a float, but an integer, how is that done ??
  2. Type Cast
    Hi: Does anyone know where I can find a good tutorial on type casting objects?
  3. cast null to integer
    I get a integer valuea from SQL Sever stored procedure OUTPUT parameter. The value is casted into integer and pass to a variable. The problem is the value in the database can be null. How should I handle it? var1 = (int) parameterInteger1.Value
  4. Casting
    Hi all I would like to prepare some generic code but I hit problem in casting. In the 4th statement, the "(java.lang.Integer)" is hardcoded to achieve casting. Is there any means for dynamic casting? >>>>>>>>>>>>>> Class...

Free Tech Articles

  1. WARNING: 5 Reasons why you should NEVER fix a computer for free.
    It is in our nature to love the puzzle. We are obsessed. The lot of us. We love puzzles. We love the challenge. We thrive on finding the answer. We hate disarray. It bothers us deep in our soul. W...
  2. SCCM OSD Basic troubleshooting
    SCCM 2007 OSD is a fantastic way to deploy operating systems, however, like most things SCCM issues can sometimes be difficult to resolve due to the sheer volume of logs to sift through and the dispe...
  3. Migrate Small Business Server 2003 to Exchange 2010 and Windows 2008 R2
    This guide is intended to provide step by step instructions on how to migrate from Small Business Server 2003 to Windows 2008 R2 with Exchange 2010. For this migration to work you will need the fo...
  4. Create a Win7 Gadget
    This article shows you how to create a simple "Gadget" -- a sort of mini-application supported by Windows 7 and Vista. Gadgets can be dropped anywhere on the desktop to provide instant information, ...
  5. Outlook continually prompting for username and password
    There have been a lot of questions recently regarding Outlook prompting for a username and password whilst using Exchange 2007. There are a few reasons why this would happen and I will try to cover t...
  6. Backup Exchange 2010 Information Store using Windows Backup
    There seems to be quite a lot of confusion around the ability to backup Exchange 2010 using the built in Windows Backup feature. This stems from the omission of this feature prior to Exchange 2007 s...

Cloud Class Webinars

  1. Avoiding Bugs in Microsoft Access
    Alison Balter takes and in-depth look at avoiding bugs in Access. In this webinar you will learn about using the immediate window to debug your applications, invoking the debugger, using breakpoints to troubleshoot, stepping through code, setting the next statement to execute, ...
  2. Top 10 Best New Features in Visio 2010
    Scott Helmers gives live demonstrations of the top 10 new features in Visio 2010. This webinar will teach you how to create compelling diagrams by adding shapes to the page with a single click, linking the shapes in a diagram to data in Excel (or SQL Server, or SharePoint), ...
  3. IT Consultant Business Secrets Revealed
    Michael Munger, Experts Exchange tech pro and IT consultant, pulls back the curtain on his very successful businesses and answers question on every IT consultant and business owner should know about. He shares secrets on what he did to solve the 5 most common problems in IT, ...
  4. Disaster Recovery and Business Continuity
    Quest CTO, Mike Billon, gives an overview of the steps involved in building a dunamic disaster recovery plan. Through case studies and an examination of software/hardware tooles for monitoring and testing, you'll gain a better understandin of where you are, where you want ...
  5. Organize Your Visio Diagrams with Containers and Lists
    Scott Helmers uses cross functional flowcharts, wireframe diagrams, data graphic legends and seating charts to teach you: how to ustilize all three new structured diagram components in Visio 2010, the best practices for organizeing shapes in previous version of Visio, how to organize ...
  6. How to Us Objects, Properties, Events and Methods in Microsoft Access
    Alison Dalter gives an in-depbth look at objects, properties, events and methods in Microsoft Access. In this webinar you will learn about using the object browser, referring to objects, working with properties and methods, working with object variables, understanding the ...

Join the Community

Give a Little. Get a Lot.

Join the community of experts here and help other tech pros by answering question in your area of expertise. You can earn FREE access to all Experts Exchange's premium features and resources.

Join the Community

Answers

 

by: annebPosted on 2009-09-20 at 14:47:55ID: 25379127

skey is of type DBT. DBT apparently has a member 'data'. The example does not include a declaration of DBT, so the data type of member "data" is not clear. edata is of undeclared type "Comparex" and has a member "val1". According to the question val1 is of type long.

Looking at the error message it is seems  that:

- data is a pointer to some data type (char* (?), long* (?))
- val1 is of type integer

You should normally not assign a pointer to some data to an integer value.

if data is of type long* you should rewrite the line to:

*(skey->data) = edata1->val1;





 

by: TwentyFourSevenPosted on 2009-09-20 at 14:53:21ID: 25379153

This is Berkely DB, so  const DBT *data refers to the primary db record's data.

The data field in my primary db is being inserted as type Comparex.

typedef struct
{
long    id;
long    val1;
long    val2;
long    val3;
long    val4;
} Comparex;

 

by: Infinity08Posted on 2009-09-20 at 15:44:41ID: 25379335

The point is that you're trying to assign a long value to a pointer type. The compiler doesn't allow that (for obvious reasons). It indicates that you likely made a mistake that needs fixing.

What's the exact type of skey->data ?

 

by: TwentyFourSevenPosted on 2009-09-20 at 16:01:40ID: 25379396

Probably easiest if I show the example I was trying to work from...

http://www.oracle.com/technology/pub/articles/seltzer-berkeleydb-sql.html

To save you reading through....

"The callback function takes a key/data pair and returns a DBT that references the value to be used as a secondary key.
So, in order to create the secondary index on last_name, you must write a callback function that takes a key/data pair and returns a DBT referencing the last_name field of that data item. ".

The example they give is below.

int
lname_callback(DB *dbp, const DBT *key, const DBT *data, DBT *skey)
{
	emp_data	*edata;
	
	/*
	 * We know that the opaque byte-string represented by the data DBT
	 * represents one of our emp_data structures, so let's cast it
	 * to one of those so that we can manipulate it.
	 */
	
	edata = data->data;
	
	skey->data = edata->lname;
	skey->size = strlen((edata->lname);
	
	return (0);
}
                                              
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:

Select allOpen in new window

 

by: TwentyFourSevenPosted on 2009-09-20 at 16:03:43ID: 25379400

So the answer to the question you're probably looking for is that skey is a DBT and a DBT is a structure  used by Berkeley DB when manipulating keys or data.

 

by: TwentyFourSevenPosted on 2009-09-20 at 16:05:20ID: 25379406

BTW, my use of memset comes from the actual docs example, below....

http://www.oracle.com/technology/documentation/berkeley-db/db/gsg/C/keyCreator.html

#include <db.h>
 
...
 
int
get_sales_rep(DB *sdbp,          /* secondary db handle */
              const DBT *pkey,   /* primary db record's key */
              const DBT *pdata,  /* primary db record's data */
              DBT *skey)         /* secondary db record's key */
{
    VENDOR *vendor;
 
    /* First, extract the structure contained in the primary's data */
    vendor = pdata->data;
 
    /* Now set the secondary key's data to be the representative's name */
    memset(skey, 0, sizeof(DBT));
    skey->data = vendor->sales_rep;
    skey->size = strlen(vendor->sales_rep) + 1;
 
    /* Return 0 to indicate that the record can be created/updated. */
    return (0);
} 

                                              
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:

Select allOpen in new window

 

by: annebPosted on 2009-09-20 at 16:07:02ID: 25379409

According to the documentation a DBT struct has a member

void* data;

Your assignment should then be:

skey->data = &(edata1->val1);.

after this, pointer skey->data points to the address of edata1->val1

 

by: TwentyFourSevenPosted on 2009-09-20 at 16:15:08ID: 31631232

Just when I thought I was getting to understand all this stuff about pointers, references  etc. !

I'm starting to see the power of C ... but it's unfortunately hidden behind much complexity !

Thank you anneb !

 

by: annebPosted on 2009-09-20 at 16:23:13ID: 25379450

hmm, it seems that skey->data should always contain a string value.
So you need to convert the long value to a string.

You could do something like this:
// create a temporary buffer that remains available after the function returns
static char temp[100];
// convert edata1 to string
sprintf (temp, "%ld", edata1->val1);

// assign to DBT struct
skey->data = temp;
skey->size = strlen(temp) + 1;

20120131-EE-VQP-002

3 Ways to Join

30-Day Free Trial

The Experts

98% positive feedback on 31,087 answers since March 2000. angeliii is a Microsoft Most Valuable Professional for his work with MS SQL Server & Develoment.

He has also proven his knowledge of Visual Basic Programming, PHP Scripting and Oracle Databases.

The Experts

97% positive feedback on 10,752 answers since July 2000. lrmoore has more than 18 years experience in the networking industry.

The six-time Mircosoft MVPs specialties include firewalls, virtual private networking, and network management.

Testimonials

"...and excellent source for support... Kind of like having your very own IT dept." Electriciansnet

Testimonials

"I was apprehensive at signing up at first. However... it has already made my life as an IT administrator much easier." JaCrews

Testimonials

"WOW! You guys have great, active, and knowledgeable people on here." moore50

Business Clients

Business Clients

In the Press

"If you’ve got a question... Experts Exchange can supply an answer.”

In the Press

"...an invaluable aid for both IT professionals and those who require tech support."

In the Press

"where IT professionals provide quick answers on just about any topic"

Business Account Plans

Loading Advertisement...