convert from data structure to array of strings & sort

[ronenk]

I have data struct of Citizens I need to transfer them to array of string, then sort that array.
This is what I wrote:

ConSort(PERSON arr[TOT])
{
	int i=0, j;
	char *temp=NULL, **Lname[TOT];
	while (arr[i].Lname)
		strcpy (*Lname[i],arr[i].Lname);

	for (i=0;i<TOT;i++)
		for (j=0;j<TOT;j++)
			if (strcmp(*Lname[j], *Lname[i])>0);
			 {
				temp=*Lname[j];
				*Lname[j]=*Lname[j+1];
				*Lname[j+1]=temp;
			 };
}

In debbuger I get :
Unhandled exception in "filename" access violation
right in the begining of the function
TIA,

Ronen

[quzah]

	char *temp=NULL, **Lname[TOT];
	while (arr[i].Lname)
		strcpy (*Lname[i],arr[i].Lname);

You don't have any space allocated, you just blindly start copying strings into wherever those pointers happen to point. This accesses random locations in memory, giving you an access violation.

Try allocating space for the string before you copy to it.

while( arr[i].Lname )
{
    *Lname[i] = malloc( strlen( arr[i].Lname ) + 1 );
    strcpy( *Lname[i], arr[i].Lname );
}

Furthermore, in your loop (and the one I have above), you never actually increment i, so it's going to hang on an infinite loop. Be sure you free everything you allocate.

Also, know that as soon as this function ends, everything you've allocated is going to be lost, because it's in a global variable and you're not returning a pointer to it anywhere.

Quzah.

[ronenk]

fixed the things Quzah wrote & others. The new version:

char *ConSort(PERSON arr[TOT])
{
	int i=0, j;
	char *temp=NULL, **Lname[TOT];

	while( i<TOT )
		{
			*Lname[i] = (char*) malloc( strlen( arr[i].Lname ) + 1 );
			strcpy( *Lname[i], arr[i].Lname );
			i++;
		}

	for (i=0;i<TOT;i++)
		for (j=0;j<TOT;j++)
			if (strcmp(*Lname[j], *Lname[j+1])>0);
			 {
				temp=*Lname[j];
				*Lname[j]=*Lname[j+1];
				*Lname[j+1]=temp;
			 };
			 return **Lname;
			 free(Lname);
}

still same old error in the begining of the first while loop.

Ronen