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Views: 3955 | Replies: 7
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Join Date: Jul 2007
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Newbie Poster
I keep getting this warning every time I compile the following code.
Can anyone please tell me what I am doing wrong.
Also, the printf(head->data) keeps saying that printf's argument is invalid. How do I print head's data?
Any help is appreciated.
Thanks,
Can anyone please tell me what I am doing wrong.
Also, the printf(head->data) keeps saying that printf's argument is invalid. How do I print head's data?
Any help is appreciated.
Thanks,
#include<stdio.h>
#include<malloc.h>
typedef struct
{
int data;
struct element *next;
}node;
main()
{
node *head;
insert(&head);
printf(head->data);
}
insert(node **head)
{
node *newElem;
newElem= (node *)malloc (sizeof(node));
if(!newElem)
{
return 0;
}
newElem->next=head;
head=newElem;
head->data=45;
return 1;
}
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Join Date: Oct 2007
Posts: 62
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Junior Poster in Training
>printf(head->data);
printf takes a string as the first argument, not an integer. You probably just forgot to add the format string, which would make the line look like this:
If you don't mind, I'll make a few unrelated comments:
>#include<malloc.h>
malloc.h isn't a standard header, and it's certainly not the one you should be including for malloc. Include stdlib.h instead.
>main()
The best definition of main is:
This guarantees that you'll be able to compile now and in the forseeable future. Also, when you omit the return type, it's int. Just because you didn't say int explicitly doesn't mean you can omit the actual return value too.
>insert(node **head)
Once again, be sure to be explicit about your return types.
>newElem= (node *)malloc (sizeof(node));
This isn't built for maintenance. If you decide to change the name of the structure ("node" is surprisingly popular, and C doesn't handle naming conflicts very well), you have to change each and every occurrence of it in your code. You can get rid of the specific type entirely by doing this:
The cast isn't required in C, and because sizeof doesn't evaluate the operand, you can dereference the pointer all you want and nothing bad will happen. The plus side is that this trick is an easy way of getting the size of the thing a pointer points to without knowing ahead of time. 
printf takes a string as the first argument, not an integer. You probably just forgot to add the format string, which would make the line look like this:
c Syntax (Toggle Plain Text)
If you don't mind, I'll make a few unrelated comments:
>#include<malloc.h>
malloc.h isn't a standard header, and it's certainly not the one you should be including for malloc. Include stdlib.h instead.
>main()
The best definition of main is:
c Syntax (Toggle Plain Text)
>insert(node **head)
Once again, be sure to be explicit about your return types.
>newElem= (node *)malloc (sizeof(node));
This isn't built for maintenance. If you decide to change the name of the structure ("node" is surprisingly popular, and C doesn't handle naming conflicts very well), you have to change each and every occurrence of it in your code. You can get rid of the specific type entirely by doing this:
c Syntax (Toggle Plain Text)
Last edited by Ptolemy : Oct 31st, 2007 at 5:13 pm.
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Join Date: Jul 2007
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Newbie Poster
Thank u so much, I feel like a dumbass for writing such bad code 
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Join Date: Oct 2007
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Junior Poster in Training
>I feel like a dumbass for writing such bad code
It's not that bad...
It's not that bad...
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Join Date: Oct 2007
Location: Cherry Hill, NJ
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I hope that your struct was just missing the element part:
You aren't likely to compile properly if you use struct element without first tagging it...
Hope this helps.
typedef struct element
{
int data;
struct element *next;
} node;You aren't likely to compile properly if you use struct element without first tagging it...
Hope this helps.
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Join Date: Jul 2007
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Newbie Poster
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Originally Posted by Duoas 
I hope that your struct was just missing the element part:
typedef struct element { int data; struct element *next; } node;
You aren't likely to compile properly if you use struct element without first tagging it...
Hope this helps.
That's weird because my program is working even without doing it.
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Join Date: Dec 2005
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> That's weird because my program is working even without doing it
Seems to me that you're compiling your C code with a C++ compiler then.
Try renaming your prog.cpp file to be prog.c then see what happens.
Seems to me that you're compiling your C code with a C++ compiler then.
Try renaming your prog.cpp file to be prog.c then see what happens.
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Join Date: Jul 2007
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Newbie Poster
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Originally Posted by Salem
> That's weird because my program is working even without doing it
Seems to me that you're compiling your C code with a C++ compiler then.
Try renaming your prog.cpp file to be prog.c then see what happens.
My bad, I guess when I copy pasted the code it somehow got lost.
I have it in my program. Thanks guys!!
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