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From: Jonathan de Boyne Pollard on 5 Apr 2010 19:45
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<p wrap="">I am facing a weird issue here.<br>
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<p>A quick review indicates that this is little more than a simple
variation on <a
href="http://homepage.ntlworld.com./jonathan.deboynepollard/FGA/dll-design-mistakes-to-avoid.html">one
of the commonplace DLL design mistakes to avoid</a>.� You're mixing and
matching heaps.� You're getting heap corruption, manifesting itself as
odd behaviour of your string class.� Just as the Frequently Given
Answer told you that you would.<br>
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From: David Schwartz on 5 Apr 2010 23:04
On Apr 5, 4:45 pm, Jonathan de Boyne Pollard <J.deBoynePollard-
newsgro...(a)NTLWorld.COM> wrote:

> A quick review indicates that this is little more than a simple variation on
> one of the commonplace DLL design mistakes to avoid.  You're mixing and
> matching heaps.  You're getting heap corruption, manifesting itself as odd
> behaviour of your string class.  Just as the Frequently Given Answer told you
> that you would.

Bingo! If X allocates the memory, X should free the memory.

So when an application calls into a DLL, one of three things should
happen:

1) The application allocates the memory before calling the DLL. The
application can free the memory at its leisure using a free function
compatible with however it allocated the memory.

2) The application provides the DLL with hooks it should use to
allocate any memory it needs to hand over to the application. The
application then frees that memory (with a method compatible with the
hooks it provided the DLL) at its leisure.

3) The DLL provides the application with a "free object" call. The DLL
returns an object to the application that the application can free by
calling the DLL's "free object" function. The DLL uses a a freeing
method that is compatible with how it allocates the objects.

But what the OP did is had the DLL allocate the memory however it
wanted to and then had the application free the memory however it
wanted to. There is no guarantee these two methods will be at all
compatible. This is a big no-no.

If X allocates the memory, X should free the memory.

DS
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