[gobo-eiffel-develop] Bug in class READABLE_STRING_8

[Wolfgang J. <wo....@ka...>]

Hi Eric,

I found an fatal error in routine READABLE_STRING_8.copy if the argument 
is a non-void but empty string. The origin text is as follows:

     copy (other: like Current)
             -- Reinitialize by copying the characters of `other'.
             -- (This is also used by `twin'.)
         local
             old_area: like area
         do
             if other /= Current then
                 old_area := area
                 standard_copy (other)
                     -- Note: <= is needed as all Eiffel string should 
have an
                     -- extra character to insert null character at the end.
                 if old_area = Void or else old_area = other.area or 
else old_area.count <= count then
                         -- Prevent copying of large `area' if only a 
few characters are actually used.
                     area := area.resized_area (count + 1)
                 else
                     old_area.copy_data (area, 0, 0, count)
                     area := old_area
                 end
                 internal_hash_code := 0
             end
         ensure then
             new_result_count: count = other.count
             -- same_characters: For every `i' in 1..`count', `item' 
(`i') = `other'.`item' (`i')
         end


If the string to copy is empty, i.e. `old_area=Void' then `area' is 
void, too,
after `standard_copy'. Then branch `if old_area=Void or else ...' leads 
to instruction `area := area.resized_area (count + 1)' that must crash. 
I propose the following modification (it works fine for me):


     copy (other: like Current)
             -- Reinitialize by copying the characters of `other'.
             -- (This is also used by `twin'.)
         local
             old_area: like area
         do
             if other /= Current then
                 old_area := area
                 standard_copy (other)
                     -- Note: <= is needed as all Eiffel string should 
have an
                     -- extra character to insert null character at the end.
                 if old_area = Void then
                 elseif old_area = other.area or else old_area.count <= 
count then
                         -- Prevent copying of large `area' if only a 
few characters are actually used.
                     area := area.resized_area (count + 1)
                 else
                     old_area.copy_data (area, 0, 0, count)
                     area := old_area
                 end
                 internal_hash_code := 0
             end
         ensure then
             new_result_count: count = other.count
             -- same_characters: For every `i' in 1..`count', `item' 
(`i') = `other'.`item' (`i')
         end


I do not know whether the bug is already in ISE's distribution of the 
class.

Best regards
Wolfgang

-- 
Dr. Wolfgang Jansen
Lauenburger Straße 40
D-12169 Berlin

Tel: (+49) 0172 40 86 916
e-mail: wo....@ka...