structure pointers

**Richard Heathfield** · Oct 30 '06, 07:05 AM

Re: structure pointers

raghu said:

Hello
>
This is Raghu. I have a problem in the pointers.
The code is
typedef struct Tlv{
/*type Length value for each
message */
unsigned char ucType; /*Type varies from message to
message */
unsigned short usLength;/*Length */
unsigned int ucValue;/*Value*/
}tlv;
>
>
typedef struct te{
char d;
int e;
}Q;
struct temp{
int a;
unsigned int c;
Q *q;
tlv *T;
};
struct temp t;
t.a = 4;

Here's your problem. You can't have executable code except inside a
function.

t.c = 31;

This breaks for the same reason.

t.q[0].d =21;

This breaks for the same reason, but also because t.q doesn't point anywhere
useful (or if it was statically initialised, it has the value NULL). Either
way, t.q[0] is an illegal memory access.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)

**raghu** · Oct 30 '06, 07:25 AM

Re: structure pointers

Richard Heathfield wrote:

raghu said:
>

Hello

This is Raghu. I have a problem in the pointers.
The code is
typedef struct Tlv{
/*type Length value for each
message */
unsigned char ucType; /*Type varies from message to
message */
unsigned short usLength;/*Length */
unsigned int ucValue;/*Value*/
}tlv;

typedef struct te{
char d;
int e;
}Q;
struct temp{
int a;
unsigned int c;
Q *q;
tlv *T;
};
struct temp t;
t.a = 4;

>
Here's your problem. You can't have executable code except inside a
function.
>

t.c = 31;

>
This breaks for the same reason.
>

t.q[0].d =21;

>
This breaks for the same reason, but also because t.q doesn't point anywhere
useful (or if it was statically initialised, it has the value NULL). Either
way, t.q[0] is an illegal memory access.
>
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)

But even I modified the code as follows the error is repeting.
the code is
main(){
struct temp t;
t.a = 4;
t.c = 31;

t.T -ucType = 1;
t.T -usLength = 11;
t.T -ucValue = 21;
printf("The entered values are %d\n ", sizeof(t));
printf("%d\n%d\ n", t.a, t.c);
printf(" %d \n",t.T->ucType);
return 0;

}
the structure defination is same as above. By the by I am using gcc
compiler.

**Steven Kirby** · Oct 30 '06, 07:55 AM

Re: structure pointers

raghu wrote:

Richard Heathfield wrote:

>raghu said:
>>

>>Hello
>>>
>>This is Raghu. I have a problem in the pointers.
>>The code is
>>typedef struct Tlv{
>> /*type Length value for each
>>message */
>> unsigned char ucType; /*Type varies from message to
>>message */
>> unsigned short usLength;/*Length */
>> unsigned int ucValue;/*Value*/
>>}tlv;
>>>
>>>
>>typedef struct te{
>>char d;
>>int e;
>>}Q;
>>struct temp{
>>int a;
>>unsigned int c;
>>Q *q;
>>tlv *T;
>>};
>> struct temp t;
>> t.a = 4;

>Here's your problem. You can't have executable code except inside a
>function.
>>

>> t.c = 31;

>This breaks for the same reason.
>>

>> t.q[0].d =21;

>This breaks for the same reason, but also because t.q doesn't point anywhere
>useful (or if it was statically initialised, it has the value NULL). Either
>way, t.q[0] is an illegal memory access.
>>
>--
>Richard Heathfield
>"Usenet is a strange place" - dmr 29/7/1999
>http://www.cpax.org.uk
>email: rjh at above domain (but drop the www, obviously)

>
But even I modified the code as follows the error is repeting.
the code is
main(){
struct temp t;
t.a = 4;
t.c = 31;
>
>
t.T -ucType = 1;
t.T -usLength = 11;
t.T -ucValue = 21;
printf("The entered values are %d\n ", sizeof(t));
printf("%d\n%d\ n", t.a, t.c);
printf(" %d \n",t.T->ucType);
return 0;
>
>
}
the structure defination is same as above. By the by I am using gcc
compiler.
>

In the temp struct definition, you define T as a pointer to a tlv
structure, but you never actually assign it to one. You're trying to use
an undefined pointer, which is most likely why it's crashing. Either you
need to assign the T pointer to a tlv struct, or just declare T as a tlv
struct variable, not a pointer.

**raghu** · Oct 30 '06, 08:15 AM

Re: structure pointers

Steven Kirby wrote:

raghu wrote:

Richard Heathfield wrote:

raghu said:
>
>Hello
>>
>This is Raghu. I have a problem in the pointers.
>The code is
>typedef struct Tlv{
> /*type Length value for each
>message */
> unsigned char ucType; /*Type varies from message to
>message */
> unsigned short usLength;/*Length */
> unsigned int ucValue;/*Value*/
>}tlv;
>>
>>
>typedef struct te{
>char d;
>int e;
>}Q;
>struct temp{
>int a;
>unsigned int c;
>Q *q;
>tlv *T;
>};
> struct temp t;
> t.a = 4;
Here's your problem. You can't have executable code except inside a
function.
>
> t.c = 31;
This breaks for the same reason.
>
> t.q[0].d =21;
This breaks for the same reason, but also because t.q doesn't point anywhere
useful (or if it was statically initialised, it has the value NULL). Either
way, t.q[0] is an illegal memory access.
>
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)

But even I modified the code as follows the error is repeting.
the code is
main(){
struct temp t;
t.a = 4;
t.c = 31;

t.T -ucType = 1;
t.T -usLength = 11;
t.T -ucValue = 21;
printf("The entered values are %d\n ", sizeof(t));
printf("%d\n%d\ n", t.a, t.c);
printf(" %d \n",t.T->ucType);
return 0;

}
the structure defination is same as above. By the by I am using gcc
compiler.

>
In the temp struct definition, you define T as a pointer to a tlv
structure, but you never actually assign it to one. You're trying to use
an undefined pointer, which is most likely why it's crashing. Either you
need to assign the T pointer to a tlv struct, or just declare T as a tlv
struct variable, not a pointer.

Hello,

Thank Q very much. Your idea worked. I want to know which C
compiler is the best one.
please inform me.
once again Thank Q
Bye
Raghu

**Richard Heathfield** · Oct 30 '06, 08:25 AM

Re: structure pointers

raghu said:

>
I want to know which C
compiler is the best one.

Define "best".

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)

**Steven Kirby** · Oct 30 '06, 08:25 AM

Re: structure pointers

raghu wrote:

Steven Kirby wrote:

>raghu wrote:

>>Richard Heathfield wrote:
>>>raghu said:
>>>>
>>>>Hello
>>>>>
>>>>This is Raghu. I have a problem in the pointers.
>>>>The code is
>>>>typedef struct Tlv{
>>>> /*type Length value for each
>>>>message */
>>>> unsigned char ucType; /*Type varies from message to
>>>>message */
>>>> unsigned short usLength;/*Length */
>>>> unsigned int ucValue;/*Value*/
>>>>}tlv;
>>>>>
>>>>>
>>>>typedef struct te{
>>>>char d;
>>>>int e;
>>>>}Q;
>>>>struct temp{
>>>>int a;
>>>>unsigned int c;
>>>>Q *q;
>>>>tlv *T;
>>>>};
>>>> struct temp t;
>>>> t.a = 4;
>>>Here's your problem. You can't have executable code except inside a
>>>function.
>>>>
>>>> t.c = 31;
>>>This breaks for the same reason.
>>>>
>>>> t.q[0].d =21;
>>>This breaks for the same reason, but also because t.q doesn't point anywhere
>>>useful (or if it was statically initialised, it has the value NULL). Either
>>>way, t.q[0] is an illegal memory access.
>>>>
>>>--
>>>Richard Heathfield
>>>"Usenet is a strange place" - dmr 29/7/1999
>>>http://www.cpax.org.uk
>>>email: rjh at above domain (but drop the www, obviously)
>>But even I modified the code as follows the error is repeting.
>>the code is
>>main(){
>> struct temp t;
>> t.a = 4;
>> t.c = 31;
>>>
>>>
>> t.T -ucType = 1;
>> t.T -usLength = 11;
>> t.T -ucValue = 21;
>> printf("The entered values are %d\n ", sizeof(t));
>> printf("%d\n%d\ n", t.a, t.c);
>> printf(" %d \n",t.T->ucType);
>> return 0;
>>>
>>>
>>}
>> the structure defination is same as above. By the by I am using gcc
>>compiler.
>>>

>In the temp struct definition, you define T as a pointer to a tlv
>structure, but you never actually assign it to one. You're trying to use
>an undefined pointer, which is most likely why it's crashing. Either you
>need to assign the T pointer to a tlv struct, or just declare T as a tlv
>struct variable, not a pointer.

>
Hello,
>
Thank Q very much. Your idea worked. I want to know which C
compiler is the best one.
please inform me.
once again Thank Q
Bye
Raghu
>

That's pretty much a matter of opinion. Personally, I use MinGW (a
Windows port of the GCC compiler, and some other tools) for console and
SDL programming, but I find Visual C++ to be much handier for Windows
programming.

I'm not sure what you're using at the moment, but Dev-C++ is a simple
and practical environment for Windows which comes bundled with MinGW.
You can get it from http://www.bloodshed.net/devcpp.html

**Fred Kleinschmidt** · Oct 30 '06, 04:05 PM

Re: structure pointers

"raghu" <ragavakumar@gm ail.comwrote in message
news:1162192614 .605043.263510@ m7g2000cwm.goog legroups.com...

Hello
>
This is Raghu. I have a problem in the pointers.
The code is
typedef struct Tlv{
/*type Length value for each
message */
unsigned char ucType; /*Type varies from message to
message */
unsigned short usLength;/*Length */
unsigned int ucValue;/*Value*/
}tlv;
>
>
typedef struct te{
char d;
int e;
}Q;

struct temp{
int a;
unsigned int c;
Q *q;
tlv *T;
};

struct temp t;
t.a = 4;
t.c = 31;
t.q[0].d =21;
t.q[0].e = 23;
t.q[1].d = 11;
t.q[1].e = 4;
>

Another problem here. What is t.q?
You have not assigned q to point anywhere

>
t.T -ucType = 1;
t.T -usLength = 11;
t.T -ucValue = 21;
printf("The entered values are ");
printf("%d\n%d\ n", t.a, t.c);
printf(" %d \n", t.q[0].d);
printf(" %d \n",t.T->ucType);
return 0;
}
when I run this program some error is generating that is Segmentation
fault.
Can you please help me.
Thanks in advance.
>
-Bye
Raghu
>

--
Fred L. Kleinschmidt
Boeing Associate Technical Fellow
Technical Architect, Software Reuse Project

structure pointers

structure pointers

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