delphi dll最终化：如何调试

Question

I have a problem in a dll (including a COM object): when the dll is unloaded some finalization sections are executed and some are not.

in the debugger I could manage to locate the problem in System FinalizeUnits(). pseudo code of this function - for your convenience:

procedure FinalizeUnits;
var
  Count: Integer;
  Table: PUnitEntryTable;
  P: Pointer;
begin
  if InitContext.InitTable = nil then
    exit;
  Count := InitContext.InitCount;
  Table := InitContext.InitTable^.UnitInfo;
  try
    while Count > 0 do
    begin
      Dec(Count);
      InitContext.InitCount := Count;
      P := Table^[Count].FInit;
      if Assigned(P) and Assigned(Pointer(P^)) then
      begin
        // ISSUE: when this is called for item x the debugging just stops
        // breakpoints in the except block or at the end of the function are not reached!
        TProc(P)(); 
      end;
    end;
  except
    FinalizeUnits;  { try to finalize the others }
    raise;
  end;
end;

there is one specific finalization call that causes the problem:
ie the InitContext.InitCount is about 400 and when item x (eg 363) is executed, the debugger just stops: it does not proceed to the except block and also not to the end of the FinalizeUnits() function (where I have set breakpoints).
BTW: how is that possible? I thought the except block (or the line after it) must be called in any case.

notes:

• when I manually avoid this special call, all other functions are executed normally.
• when I step into the problematic TProc I end up in TCriticalSection.Enter (then Acquire - FSection.Enter - EnterCriticalSection - WSACleanup )

some more info to the WSACleanup call: I use a 3rd party library UniDAC that opens a TCP/IP connection to a database - I think this library calls WSACleanup in one of it's finalization sections (but I don't have this source code). The strange thing is, that when the debugger is on the WSACleanup line:

function WSACleanup;        external     winsocket name 'WSACleanup';

and I want to step over it (ie F8), the debugger just stops (as if the application had exited normally) - but it should continue the loop in FinalizeUnits : how is this possible? ie if it were a deadlock it would not stop, but hang forever, right?

The question is: how can I debug this issue? is it possible that a deadlock causes this problem (ie that the debugger just stops)?

Answer 1

Try switching to CPU view before stepping into the problematic TProc using F7. Sometimes this can give you a good hint.

You could also try looking up the address of "P" in the map file.