Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!udel!brahms.udel.edu!stas
From: stas@brahms.udel.edu (Stanislaus Pietrucha)
Newsgroups: comp.sys.mac.programmer
Subject: Think C bug
Message-ID: <21514@brahms.udel.edu>
Date: 19 May 91 20:42:08 GMT
Distribution: usa
Organization: University of Delaware
Lines: 92

This is the weirdest I've ever seen, and I know it is a compiler error.
First of all I compiled the code in Think C and, what you see here works.
The problem is the field in the record struct, int dummy.  

If i try to run this code without the dummy field, it will crash whenever
I reference char last[24] (as i do in fgets(...p_current->last)).

If this isn't weird enough, if I switch the order of the fields in the record,
the error (bad field) is always the same. i.e. if i moved first where last is
then i could access last, but not first.  It's like a black hole.  Without
the dummy variable exactly where it is, whatever item (it seems) that is in
the 5th position is inaccessable.  What the heck is going on????

Take a look at the code:  
 
Here is the record structure:
struct customer_record
	{
	struct customer_record *prev;
	struct customer_record *next;
	char number[8];
	char first[20];
	int dummy;
	char last[24];
	char position[8];
	char team[40];
	char rookie[8];
	char sale[8];
	int quantity;
	};
 
here is the function in which the program blows up (when dummy not used) 
 
int file_to_list(FILE *datafile,struct customer_record *llist)
{
	char last[24],file_header[40];
	struct customer_record *p_current;
	int c, x, done, length = 0;
	int quantity;
	p_current = (struct customer_record *) malloc(sizeof
				(struct customer_record));
	llist = p_current; 
	p_current->prev = llist;
	fgets(file_header,40,datafile);
	printf("%s\n",file_header);
	while((c=getc(datafile)) != EOF)
	{
		ungetc(c,datafile);
		fgets(p_current->number,8,datafile);
		fgets(p_current->first,20,datafile);
		fgets(p_current->last,24,datafile);
		fgets(p_current->position,8,datafile);
		fgets(p_current->team,40,datafile);
		fgets(p_current->rookie,8,datafile);
		fgets(p_current->sale,8,datafile);
		fscanf(datafile,"%d\n",p_current->quantity);
		p_current->next = (struct customer_record *) malloc(sizeof
					(struct customer_record));
		p_current->next->prev = p_current;
		p_current = p_current->next;
	} 
	fclose(datafile);
	load_flag = 1;
}
 
 
--------------------And here is the data file:
Stan's Client List			/*file_header*/
1					/*number*/
Terri					/*first*/
Wache					/*last*/
HM					/*postition*/
Nashua Hornets				/*team*/
Y					/*rookie*/
N					/*sale*/
5					/*quantity*/
2				
Carol
Veach
MG
Philadelphia Waxers
N
N
6
-------------That's it
(The comments are for you, i.e. they are not actually in the data file)
 
Don't try to make sense of the data, it's personal.
 
Thanks for any help/input you can give me.
 
Stas