Re: C Question: TypeDefing a structure ?

From:

=?Utf-8?B?Um9iYnk=?= <Robby@discussions.microsoft.com>

Newsgroups:

microsoft.public.vc.language

Date:

Mon, 25 Aug 2008 21:04:01 -0700

Message-ID:

<D7A6022C-7056-4149-9032-26E96C5BF9F7@microsoft.com>

Hello Vladimir:

It is better to declare the function DDLB* ULC_DDLB_LIB_config_DDLB as
DDLB* ULC_DDLB_LIB_config_DDLB
( enum OBJECTTASK OBJECT_CONTROL,
long CURR_ICON_NUM);

As simple as this may be, it is important to me because I have developped a
habit in enumerating many things in my code. I appreciate your recomendation,
I think I will do it as you say!

===================================xxx.c
/* many enumerations here */
enum OBJECTTASK {e_CREATE=1, e_MODIFY, e_FREE};
enum SCREEN {e_FIRST=1, e_SECOND, e_THIRD};
enum BUTTONTYPE {e_SMALL=1, e_MEDIUM, e_LARGE};

yyy(enum OBJECTTASK OT, enum SCREEN SCRN, enum BUTTONTYPE BTT)
{
//Does stuff based on the passed in parameters!
}

int main( void )
{
yyy(e_MODIFY, e_SECOND, e_LARGE);
}
============================================

Instead of:
===================================xxx.c
/* many enumerations here */
enum OBJECTTASK {e_CREATE=1, e_MODIFY, e_FREE};
enum SCREEN {e_FIRST=1, e_SECOND, e_THIRD};
enum BUTTONTYPE {e_SMALL=1, e_MEDIUM, e_LARGE};

yyy(int OT, int SCRN, int BTT)
{
//Does stuff based on the passed in parameters!
}

int main( void )
{
yyy(e_MODIFY, e_SECOND, e_LARGE);
}
============================================

This way I can clearly see where my function parameters come from and their
type!
Thankyou Vladimir!

--
Best regards
Robert

"Vladimir Grigoriev" wrote:

Of course you may include a c file inside another c file if you want that
the compilation unit contains all your files together. However it will
confuse other programmers who will deal with your project as the discusiion
has showed

Also you need not to specify extern for the obj_DDLB if it is used inside
one compilation unit. However in this case it is better to declare obj_DDLB
as static. In ttis case it will be a module-wide global variable.

According to the C-standard it is better to declare the main function as

int main( void )

It is better to declare the function DDLB* ULC_DDLB_LIB_config_DDLB as
DDLB* ULC_DDLB_LIB_config_DDLB
( enum OBJECTTASK OBJECT_CONTROL,
  long CURR_ICON_NUM);

Inside the function DDLB* ULC_DDLB_LIB_config_DDLB instead of

obj_DDBL = (DDLB*) malloc (sizeof (struct ddListBox));

it is better to write

obj_DDLB = (DDLB*) malloc (sizeof (DDLB ));

The identifier obj_DDBL is undefined!

The same is valid for the statements below i.e. the identifier obj__DDBL is
undefined.

   case e_MODIFY:
      obj_DDBL->CURR_ICON_NUM= CURR_ICON_NUM;
      return obj_DDBL;
   break;
   case e_FREE:
      free(obj_DDBL);
   break;
   }

Also in the case of e_FREE you did not return a DDLB *.

In the statement

void ULC_DDLB_LIB_do_DDLB( DDLB *obj_DDLB)
{//NO CODE }

youi will get a compilation error because you commented the lines '//NO
CODE }' in whole. You should use C comment symbols

{ /* NO CODE */ }

Vladimir Grigoriev

"Robby" <Robby@discussions.microsoft.com> wrote in message
news:8FD11D01-4D18-476F-81AC-CFF86AE07F26@microsoft.com...

Hello,

I have recently created my own way of manipulating the informations in a
structure and has worked very well.... until today! I am sure many
individuals had this idea and at one point or another tried this or even
adopted it.. it really is a no brainer.

I don't know... perhaps this is not the way to do things, however, it did
work for several structures in my project but this last structure has
generated errors. I have tried dozens of tests, but can't seem to find the
source of the errors. The other four structures in my project (not shown
here, however are an exact carbon copy only different names) are
manipulated
this way and are flawless in terms of functionality, errors or warning
messages.

Basically, I typedef a structure and create a global pointer of the that
type (which is of the structure's type) and then when I want to create an
object of that structure, I fecth a function which creates the object on
the
heap using malloc. The function accepts an object command parameter which
tells how the logic in the function is to be executed. Basically the
function
either creates, modifies or frees the object's data.

The errors that are generated are:
Line 10 (16,24) Unidefined identifier obj_DDLB
Line 13 ( 7,15) Unidefined identifier obj_DDLB
Line 14 (14,22) Unidefined identifier obj_DDLB
Line 18 (12,20) Unidefined identifier obj_DDLB

How can this be when "obj_DDLB" is declared globally?????

These are the errors that my MCU's compiler generates.
Thanking everyone in advance as all feedback and help is very, very
appreciated!

Here is the sample code:

==============================================ACM152.h
enum OBJECTTASK {e_CREATE=1, e_MODIFY, e_FREE};

==============================================ACM152.c
#include <ACM152.h>
#include <API_DDLB_LIB.h>
#include <API_DDLB_LIB.c>

void main()
{
obj_DDLB = ULC_DDLB_LIB_config_DDLB (e_CREATE, 0);
ULC_DDLB_LIB_do_DDLB(obj_DDLB);
ULC_DDLB_LIB_config_DDLB (e_FREE, 0);
}

==========================================API_DDLB_LIB.h
typedef struct ddListBox{
long CURR_ICON_NUM;
} DDLB;

DDLB *obj_DDLB;

DDLB* ULC_DDLB_LIB_config_DDLB
( int OBJECT_CONTROL,
long CURR_ICON_NUM);

void ULC_DDLB_LIB_do_DDLB (DDLB *obj_DDLB);

==========================================API_DDLB_LIB.c
DDLB* ULC_DDLB_LIB_config_DDLB(
int OBJECT_CONTROL,
long CURR_ICON_NUM)
{
switch (OBJECT_CONTROL)
  {
  case e_CREATE:
     obj_DDBL = (DDLB*) malloc (sizeof (struct ddListBox));
  case e_MODIFY:
     obj_DDBL->CURR_ICON_NUM= CURR_ICON_NUM;
     return obj_DDBL;
  break;
  case e_FREE:
     free(obj_DDBL);
  break;
  }
}

void ULC_DDLB_LIB_do_DDLB( DDLB *obj_DDLB)
{//NO CODE }
===================================================

--
Best regards
Robert