🚀 go-pugleaf

Last week we finally received the Apollo version of Objective-C 4.0.

A bug in the expand method of the Set class is still not solved, despite
several bug reports since August 1988 ( Objective-C version 3.3 ).
I know that the expand method is private but this method is used
by the add: and find: methods, which are public and frequently used.

In method expand the variable 'limit' is set to a value that is 1 to
high, This can cause writing above the array bound of the contents.
An example is:

=========================================================================

#import "String.h"
#import "Set.h"

main()
{
   id aString, seq;
   id x = [String str:"1"];
   id y = [String str:"1"];
   id s = [Set new:2];       // capacity of set is 4

   [x charAt:0 put:'G'];     // hash number 71, 71 % 8 == 7
   [y charAt:0 put:'O'];     // hash number 79, 79 % 8 == 7

   [s add:x];                // s has at slot 0: y
   [s add:y];                //   and at slot 3: x

   printf( "contents of s before expansion:\n" );
   seq = [s eachElement];
   while ( aString = [seq next] ) {
      printf( "%s\n", [aString str] );
   }
   [seq free];

   [s expand];

   // during expansion first y will be placed at slot 7, because the
   // capacity of s is now 7; then x will be hashed to slot 7 also, but
   // will be positioned to slot number 8 (Which does not exist), if 
   // this 'slot' contains a zero.

   printf( "\ncontents of s after expansion:\n" );
   seq = [s eachElement];
   while ( aString = [seq next] ) {
      printf( "%s\n", [aString str] );
   }
   [seq free];
}
	
=========================================================================
The result:
=========================================================================
contents of s before expansion:
O
G

contents of s after expansion:
O

+++++++++++++++++++++++++++++++++++++++
Rinie van Haperen
Philips Research Laboratories Eindhoven