#32 Crash while gif loading

[Anonymous]

Error in BGRAGifFormat while loading attached file. "RunError(204)". Application crashed. LazPaint also crash while loading this file. Other viewers show this file correctly. I can give more gif-files that do this crash.
Sorry for bad english.

[Yuri]

Solution found!
GIFCodeTableSize increased from 4096 to 32768. Line 104 in BGRAGifFormat.pas. Works fine.
Thank you all for a wonderful project :-)

[circular]

Thank you! I have applied the change (32768 when loading, but still 4096 when writing to maximize compatibility)

[Yuri]

I found a way is better.
The data from the table with an index greater than 4096 are not used. You just need to add a check for overflow. That is now AddStr2Tab function (line 242) will record and further the index 4096, as variable stridx not limited. To avoid recording in a memory cell outside the table (which leads to a crash), I propose to add a function AddStr2Tab first line this condition:

if stridx >= GIFCodeTableSize then exit;

Works good. A GIFCodeTableSize size in 4096 - it is right, because it is no longer necessary.
The result AddStr2Tab:

  procedure AddStr2Tab(prefix: Pstr; suffix: longint);
  begin
    if stridx >= GIFCodeTableSize then exit;
    strtab^[stridx].prefix := prefix;
    strtab^[stridx].suffix := suffix;
    Inc(stridx);
    case stridx of
      0..1: codelen      := 1;
      2..3: codelen      := 2;
      4..7: codelen      := 3;
      8..15: codelen     := 4;
      16..31: codelen    := 5;
      32..63: codelen    := 6;
      64..127: codelen   := 7;
      128..255: codelen  := 8;
      256..511: codelen  := 9;
      512..1023: codelen := 10;
      1024..2047: codelen := 11;
      2048..4096: codelen := 12;
    end;
    codemask := (1 shl codelen) - 1;
  end;

[circular]

Indeed, it works fine. I have applied this on SVN.

[Yuri]

I am happy to contribute to this wonderful project. :-)