Hi All,

I encountered a strange SIGSEGV with the attached program. To reproduce the problem:

1) compile and run it.
2) select "Node #2"
3) click "Test" button, it will insert a node before the selected Node
4) close the program

There will be a SIGSEGV at the end of OnDestroy method.

This problem is reproducible under Linux amd64 and Wine and Win7 (32bit). A strange thing is that on Linux or Wine, this error only occur on Node #1 and Node #2, but on Windows, it only occur on Node #2 and Node #3.

Also, if you swap either of the 2 commented statements, this error is gone.

I suspect this is caused by the AnsiString manager. Could anyone explain why, or is this a bug?

Thanks a lot.
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Only had a quick look, please veryfy....

  Move(tv.Selected.Data^, p^, SizeOf(TNode));
   tv.Items.InsertObject(tv.Selected, 'New Node', p);

Move makes a copy of the node, including a copy of the ansistring (that is the pointer-part) in the node.
so now you have 2 strings, referring the same string data, but you never increased the ref count.

Ok, that's reasonable, however:

1) If I use Move() is there a "manual" way to increate the string ref count?

2) why the error is gone if I change this line:

    prev := tv.Items.InsertObjectBehind(prev, p^.title, p);

to this:

    prev := tv.Items.InsertObjectBehind(prev, 'Node #' + IntToStr(i), p);

3) Why this error does not happen on node #0 and #3, but only node #1 and #2?

4) Why it behaves different on Windows and Linux?

Thanks!

2013/8/24 Martin

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Ok, that's reasonable, however: 1) If I use Move() is there a "manual" way to increate the string ref count?

Yes, but it is better to let the compiler do the work:
p^:=PNode(tv.Selected.Data)^;

All this has the same answer:
When you mess up the heap you get results depending on the current memory, which depends on lots of stuff. The results can vary from host to host and might not even be the same on each run. In other words: random.
Windows and Linux have different approaches how to initialize memory, so you see differences more likely.

Mattias