Gabor,
I can't duplicate your problem which probably implies that we are
looking at some weird race condition during the program tidy up phase. I
did see occasionally something like this before with Lazarus 1.6.4 on
Windows with heaptrc - but I never saw it without heaptrc and it cleared
up with Lazarus 1.8 and hence I never bothered to pursue it assuming
that it was a Lazarus bug that got fixed.
You are seeing this problem not so much with IBX, but with the Firebird
Pascal API. Your example program has excluded the IBX part and focused
purely on the API.
What might be an issue here is that the FirebirdAPI is accessed via a
COM interface and the IFirebirdAPI interface is not explicitly released.
The software just relies upon the system to clean it up at the end.
There may be a race condition here between the clear up of the interface
and the dynamic library manager. This is because when the interface is
released, it then unloads the Firebird DLL/SO. Try adding a finalization
clause to IB.pas setting "FFirebirdAPI := nil" and see if that clears it
up - or whether the exception occurs before this point.
It is not obvious if there is a real issue with cthreads. The library
should only create multiple threads when handling asynchronous Firebird
events and your program is not using this capability.
Otherwise, yes, it would be really useful to be able to find where this
exception is being raised.
Tony Whyman
MWA
On 09/03/18 09:14, Gabor Boros via Lazarus wrote:
Hi All,
The result of the attached example (which use MWA's Firebird Pascal
API) for me is an exception:
Gstat execution time Fri Mar 9 09:29:18 2018
Database header page information:
Flags 0
Generation 173
System Change Number 0
Page size 8192
ODS version 12.0
Oldest transaction 161
Oldest active 162
Oldest snapshot 162
Next transaction 164
Sequence number 0
Next attachment ID 27
Implementation HW=AMD/Intel/x64 little-endian
OS=Linux CC=gcc
Shadow count 0
Page buffers 0
Next header page 0
Database dialect 3
Creation date Feb 2, 2018 14:07:24
Attributes force write
Variable header data:
*END*
Gstat completion time Fri Mar 9 09:29:18 2018
Heap dump by heaptrc unit
355 memory blocks allocated : 948252/948432
355 memory blocks freed : 948252/948432
0 unfreed memory blocks : 0
True heap size : 131072
True free heap : 131072
An unhandled exception occurred at $00007FF97F0A3147:
EAccessViolation:
$00007FF97F0A3147
If comment out cthreads from the uses the exception is:
An unhandled exception occurred at $00007F21B71F5147:
EAccessViolation:
$00007F21B71F5147
$00007F21B71F751B
$00007F21B71F769C
$00007F21B746BFFF
If run with gdb (and cthreads):
Heap dump by heaptrc unit
355 memory blocks allocated : 948252/948432
355 memory blocks freed : 948252/948432
0 unfreed memory blocks : 0
True heap size : 131072
True free heap : 131072
[Thread 0x7ffff5991700 (LWP 2874) exited]
[Thread 0x7ffff6192700 (LWP 2873) exited]
[Thread 0x7ffff7fe3740 (LWP 2869) exited]
Cannot find user-level thread for LWP 2875: generic error
Any idea how to detect what/where is the source of the exception?
I use Linux 64bit, FPC 3.0.4 and Lazarus fixes_1_8.
Gabor
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