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From:	Martin Ambuhl <mambuhl AT earthlink DOT net>
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Subject:	Re: pointers in Strucrure assignment problem
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Date:	Thu, 07 Jul 2005 07:18:11 GMT
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aveo wrote:
> Hi all,
> Output of following program is unexpected.
> It affecting all elements of LD insted of 0th element
> Plz help me out.
[...]
> typedef struct LineDate
> {
> 	unsigned char *LinePtr;
> 	int LineCount;
> }LD1;
> 
> LD1 LD[100];
> 
> void main(void)

main returns an int in a hosted environment for either C or C++.

> {
> 	int i;
> 	//Intitialize LineData Structure---->>>>>
> 	for(i=0;i<=99;i++)
> 	{


> 		LD[i].LinePtr = (char *)calloc( 100, sizeof(char) );

sizeof(char) is 1 by definition, and, if this is C, the cast serves only 
to mask the error of not #including <stdlib.h>.  You should also test 
for the success of calloc.

> 		LD[i].LinePtr="";

The second of these causes you to
1) lose the value returned by calloc
2) create a memory leak
3) assign LD[i].LinePtr to point to the string literal "",

Further, since you used calloc, the strings are set to be empty anyway, 
so the seconde line is pointless.

A more efficient approach is

#define STRSIZE 100

    if (!(LD[i].LinePtr = malloc(STRSIZE))) { /* handle error */ }
    *LD[i].LinePtr = 0;

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