What happens to memory declared by a DLL between calls to the DLL's
routines?
Here's what I've got now, and it works just peachy in a single-user
basic app. But it crashes badly when used in a complex application.
Do you see anything wrong with this (stripped to the basics):
-- A host Delphi program calls a DLL which returns a "ref":
StartMeUp(ref);
-- The DLL reserves some memory using HeapAlloc
and returns a "reference" to the host, like this:
procedure StartMeUp(var ref: longint);
...
begin
c := HeapAlloc(GetProcessHeap, HEAP_ZERO_MEMORY, 1000);
ref := LONGINT(c);
end;
-- Then periodically, the host makes additional
calls, using that "reference", which lets the
DLL access that memory again:
DoSomething(ref, other_args);
-- Eventually, the host cleans up with a third
call to the DLL:
CleanUp(ref);
-- The DLL then disposes of this memory:
procedure CleanUp(var ref: longint);
begin
HeapFree(GetProcessHeap, 0, ref);
ref := 0;
end;
Note that the DLL does not itself maintain that "reference," not even in
a global somewhere. It's up to the host to receive it, and pass it back.
As I said, it works fine now in a straightforward app, but I'm wondering
if there is anything evil here when the thing is used in a complex
situation.
THANKS!!!!!
Kevin Killion
