Re: Ada.Strings.Fixed.Count raises Storage_Error

[Victor Porton <porton@narod.ru>]

GNAT 6.1.1 on Debian Linux "testing":

$ ./test_count 
          0          1

raised STORAGE_ERROR : stack overflow or erroneous memory access

Let's decide who of us will report the bug, so that the report won't happen 
to be duplicate?

Georg Bauhaus wrote:
> On 12.05.16 13:36, Xavier Petit wrote:
> 
>> with Ada.Strings.Fixed, Ada.Integer_Text_IO;
>> use  Ada.Strings.Fixed, Ada.Integer_Text_IO;
>>
>> procedure Test_Count is
>>     S : constant String (Positive'Last - 2 .. Positive'Last) := "Ada";
>> begin
>>     Put (Count (Source => S,                         Pattern => "AA"));
>>     Put (Count (Source => S (S'First .. S'Last - 1), Pattern => "A"));
>>     Put (Count (Source => S,                         Pattern => "A"));
>> end;
>>
>> Output on gnat-gcc 5.3.1 :
>>
>>            0          1
>>
>> raised STORAGE_ERROR : stack overflow or erroneous memory access
> 
> Compiling such that the RTS is recompiled will result in
> 
> raised CONSTRAINT_ERROR : a-strsea.adb:102 overflow check failed
> 
> The message points at a line in the implementation of
> Ada.Strings.Search.Count, for the third of the calls. It reads
> 
>       Ind := Ind + 1;
> 
> where Ind looks seems to be go along with the Index of your S,
> IINM. Effectively (PL1 = Pattern'Length - 1 being 0), then loop
> there boils down to this:
> 
>     while Ind <= Source'Last loop
>        if Pattern = Source (Ind .. Ind) then
>           ...
>        else
>           Ind := Ind + 1;
>        end if;
>     end loop;
> 
> And this would explains the overflow.
> 
> Just the slip-up that Ada subtypes were designed to help prevent?
> 
> 
-- 
Victor Porton - http://portonvictor.org