Hello,

Just try it:

var
  list: TDictionary<string, string>;
begin
  list := TDictionary<string, string>.Create(TIStringComparer.Ordinal);

Error:

An unhandled exception occurred at $000000000043A2F8: EAccessViolation: Access violation
$000000000043A2F8
$00000000004084B3 DOADD, line 277 of inc/generics.dictionaries.inc $00000000004099AB main, line 14 of project1.lpr

---

Trace:

#0
GENERICS.DEFAULTS$_$TGORDINALISTRINGCOMPARER$2$CRC09680922_$__$$_GETHASHCODE$ANSISTRING$$LONGWORD at :0
#1 ?? at :0

2016-08-17 7:05 GMT+02:00 silvioprog :

Just try it:

related to

http://bugs.freepascal.org/view.php?id=28911

Sven comment: "I won't change the current implementation for now, because once I'm going to fix this I'm going to fix this correctly for all cases, including packages, everything else is merely a workaround. But for that I first need to finish my work on packages."

btw, already reported: http://bugs.freepascal.org/view.php?id=30433

Indeed. After some debug I found where the exception is raised:

...
function TOpenAddressingLP<OPEN_ADDRESSING_CONSTRAINTS>.FindBucketIndex(constref
AItems: TArray<TItem>;
  constref AKey: TKey; out AHash: UInt32): SizeInt;
var
  LItem: {TOpenAddressing<OPEN_ADDRESSING_CONSTRAINTS>.}_TItem; // for
workaround Lazarus bug #25613
  LLengthMask: SizeInt;
  i, m: SizeInt;
  LHash: UInt32;
begin
  m := Length(AItems);
  LLengthMask := m - 1;
  LHash := FEqualityComparer.GetHashCode(AKey); // << here
...

but I can't step into FEqualityComparer.GetHashCode to check why it happens, so I'll wait for Sven too. ^^

I need to find the values using case-insensitive keys (I'm using it in a class registry of my app), so unfortunately this bug doesn't let me to use TDictionary on FPC yet. :-(

once I'm going to fix this I'm going to fix this correctly for all cases, including packages, everything else is merely a workaround. But for that I first need to finish my work on packages."

btw, already reported: http://bugs.freepascal.org/view.php?id=30433

Couldn't you work around for now by using instance instead of class variables? At least then the classes would work instead of everyone asking every second week why they don't...

Regards,
Sven

2016-08-17 16:05 GMT+02:00 silvioprog :

I need to find the values using case-insensitive keys (I'm using it in a class registry of my app), so unfortunately this bug doesn't let me to use TDictionary on FPC yet. :-(

There is simple workaround:

=== begin code ===

function EqualityComparison(constref ALeft, ARight: string): Boolean;
begin
  Result := LowerCase(ALeft) = LowerCase(ARight);
end;
procedure ExtendedHasher(constref AValue: string; AHashList: PUInt32);
begin
  TDefaultHashFactory.GetHashList(Pointer(AValue), Length(AValue) *
SizeOf(Char), AHashList);
end;
var
  list: TDictionary<string, string>;
begin
  list := TDictionary<string,
string>.Create(TEqualityComparer<string>.Construct(EqualityComparison,
ExtendedHasher));

=== end code ===

2016-08-17 17:20 GMT+02:00 Maciej Izak :

there is bug, correct version:

procedure ExtendedHasher(constref AValue: string; AHashList: PUInt32);
var
  temp: string;
begin
  temp := LowerCase(AValue);
  TDefaultHashFactory.GetHashList(Pointer(temp), Length(temp) *
SizeOf(Char), AHashList);
end;

2016-08-17 17:15 GMT+02:00 Sven Barth :

Couldn't you work around for now by using instance instead of class variables? At least then the classes would work instead of everyone asking every second week why they don't...

Yes I think that is possible :P Note: #28911 bug is most annoying ever (for generic programmers ;) )

I changed it to a function:

  function ExtendedHasher(constref AValue: string): UInt32;
  begin
    TDefaultHashFactory.GetHashList(Pointer(AValue),
      Length(AValue) * SizeOf(Char), @Result);
  end;

because the "Error: Incompatible type for arg no. 2: Got "ExtendedHasher(constref AnsiString;PDWord);", expected "<procedure variable type of function(constref AnsiString):DWord;Register>"".

Anyway, thanks for the workaround, it can fix the FPC version of my tests. :-)

2016-08-17 18:45 GMT+02:00 silvioprog :

Still bad implementation (see my previous message). Is highly probable to obtain different hashes for 'foo' and 'Foo'. Usage of GetHashList in that context is also improper, GetHashList is generally dedicated for more complicated structures (for example for cuckoo hashing). The proper code is:

  function MyHasher(constref AValue: string): UInt32;
  var
    temp: string;
  begin
    temp := LowerCase(AValue);
    Result := TDefaultHashFactory.GetHashCode(Pointer(temp), Length(temp) *
SizeOf(Char), 0);
  end;

Point for you, that was code from my memory, sorry ;) ExtendedHasher in presented form is dedicated for TExtendedEqualityComparer<T>.Construct(...) which is used for THashMap<K,V> (THashMap is much faster than TDictionary for big data)

variables? At least then the classes would work instead of everyone asking every second week why they don't...

Yes I think that is possible :P Note: #28911 bug is most annoying ever

(for generic programmers ;) )

It's also very annoying to fix correctly (for compiler developers :P )

Regards,
Sven