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C--Structures(inside structure declaration of variable of same type is not allowed)
#1
Sep 6th, 2006
It is not allowed to declare a variable of same structure type but it is allowed to declare a pointer. For example,
My question is when we can declare a pointer of same type why not a variable of same type.
I will be exremely grateful if somebody answers my question.
Thanks
Iqbal
struct node {
int a;
struct node x; //not allowed
struct node *pnext; //allowed
};My question is when we can declare a pointer of same type why not a variable of same type.
I will be exremely grateful if somebody answers my question.
Thanks
Iqbal
Last edited by WolfPack : Sep 6th, 2006 at 5:02 am. Reason: Moved the question to outside code tags.
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Re: C--Structures(inside structure declaration of variable of same type is not allowed)
#2
Sep 6th, 2006
Because if you are allowed to do so, creating one variable of that type will go on creating nested variables inside it and eat all available memory.
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Re: C--Structures(inside structure declaration of variable of same type is not allowe
#3
Sep 6th, 2006
You've basically written this
You can't infinitely expand copies of yourself when declaring a structure.
The way the cycle is broken is by having a pointer, which is always a fixed size regardless of the amount of data being pointed at.
struct node {
int a;
struct node {
int a;
struct node {
int a;
struct node {
int a;
struct node {
int a;
struct node x; // and so on....
struct node *pnext;
}x;
struct node *pnext;
}x;
struct node *pnext;
}x;
struct node *pnext;
}x;
struct node *pnext;
};The way the cycle is broken is by having a pointer, which is always a fixed size regardless of the amount of data being pointed at.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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Do not PM me for help; You'll be ignored, or told to learn to read.
Do not ask me if I'm muslim - I'm not. Nor do I care about yours or anyone else's mysticism. Religion is a matrix, take the RED PILL.
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Join Date: Aug 2006
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Re: C--Structures(inside structure declaration of variable of same type is not allowe
#4
Sep 7th, 2006
Thank you very much for the kind reply.
Last edited by WolfPack : Sep 7th, 2006 at 1:20 am. Reason: Removed the code tags from the answer. Use code tags only when you are posting code.
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