Reinier Olislagers wrote:
If the custom library never made any attempt to access Pascal-type
(long) strings, dynamic arrays, or anything else on the heap which might
be reallocated or extended when referenced (i.e. not just at creation),
then you'd not need to do anything special. But as soon as the custom
library tries to e.g. change the length of a string or dynamic array it
makes a call to the memory manager, and if it's not sharing the same
memory manager as the main app used to allocate the string/array that's
a recipe for disaster.
Yes. 3 things:
1. I hopefully fixed memory allocation issues between application<>my
dll in the previous thread. Of course if you mean my dll modifying
strings etc in the firebird .so/.dll yes of course but why don't these
problems then occur with the simpler application<>Firebird .dll/.so?
But when your code modifies strings in the context of the database
library they're preallocated C-type strings, i.e. can't be extended or
shrunk so don't make unexpected reference to any memory manager.
2. Corruption does not occur when I compile my dll with database layer
code that does not call the Firebird sqldb layer i.e. the Firebird .so/.dll
Interesting. So if I understand you correctly it's only when you've got
two levels of dynamically-loaded library, i.e. one DLL is responsible
for loading another.
Now would probably be a good time to try Postgres as an alternative.
3. I've tried both with and without cmem in both application and my dll
so they are definitely sharing the same memory manager. What the fb .so
uses... well... who knows, probably libc?!?!
Probably libc, but not really relevant since all the allocate/free
operations are done in the same context: the lib giveth, and the lib
taketh away :-)
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
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