Possible issue with Parallel.BrackgroundWorker in Delphi 13.1 and 64bit.

[MShark67]

The issue can be reproduced by running the OTL example StringListParser application in 64bit. For me it crashes on startup with
Project StringListParser.exe raised exception class $C0000005 with message 'c0000005 ACCESS_VIOLATION'.

Breaking at the exception puts you in the TOmniTaskExecutor.GetMethodAddrAndSignature procedure at the folowing place:

// Loop over the parameters
while (cardinal(params) < headerEnd) do begin
{$IFDEF OTL_KnowsParamCount}
-> if paramNum >= returnInfo.ParamCount then
break; //while

I hit that in my own applications that create similar background workers. Let me know if I can supply any more info.

[sebomozd]

The problem is in TOmniTaskExecutor.GetMethodAddrAndSignature in OtlTaskControl.pas.

This code walks RTTI using cardinal casts on pointers:

headerEnd := cardinal(methodInfoHeader) + methodInfoHeader^.Len;
returnInfo := PReturnInfo(cardinal(methodInfoHeader) + SizeOf(methodInfoHeader^) - CShortLen + Length(methodInfoHeader^.Name));
params := PParamInfo(cardinal(returnInfo) + SizeOf(TReturnInfo));
while (cardinal(params) < headerEnd) do begin

That works in 32-bit, but in 64-bit it truncates the pointer value and corrupts the RTTI traversal. As a result, returnInfo or params becomes invalid and the code crashes at:

if paramNum >= returnInfo.ParamCount then

It should be changed to pointer-sized arithmetic:

var
  headerEnd: NativeUInt;

...

headerEnd := NativeUInt(methodInfoHeader) + methodInfoHeader^.Len;
returnInfo := PReturnInfo(NativeUInt(methodInfoHeader) + SizeOf(methodInfoHeader^) - CShortLen + Length(methodInfoHeader^.Name));
params := PParamInfo(NativeUInt(returnInfo) + SizeOf(TReturnInfo));
while (NativeUInt(params) < headerEnd) do begin

So the fix is simply: replace the cardinal pointer arithmetic in that routine with NativeUInt.

[MShark67]

I can confirm that fix. Nicely done!

[TommiPrami]

Made a pull request.

Weirdly this code has been working for a long time without issue.

Maybe something changed via Windows update and/or Delphi 13.1.

#220

[gabr42]

Yes, something has changed in 13.1. And it is good that is had changed so this (last?) 64-bit compatibility bug was finally found. I fixed it over the weekend; will commit changes now.