[Lazarus] Synchronize problem in linux

[michael.vancanneyt at wisa.be]

On Wed, 25 May 2011, Mattias Gaertner wrote:

> On Wed, 25 May 2011 12:22:53 +0200 (CEST)
> michael.vancanneyt at wisa.be wrote:
>
>>
>>
>> On Wed, 25 May 2011, Giuliano Colla wrote:
>>
>>> Mattias Gaertner ha scritto:
>>>> This might help:
>>>> http://wiki.lazarus.freepascal.org/Multithreaded_Application_Tutorial
>>>>
>>>> Mattias
>>>>
>>>>
>>> I have a question related to this subject. Working with Borland's stuff
>>> (Kylix) I stumbled into a problem, and I'd like to know if the same applies
>>> also to Lazarus.
>>>
>>> I had a multithread application with a thread which receives data through a
>>> communication line. I thought it safe to use a TStringList, which AFAIK is
>>> not a visual object. The main thread would create the StringList, the other
>>> thread would append strings to the list, and when it was done, the main
>>> thread would perform the required processing. The logic of the application
>>> itself made it sure that there was no conflict whatsoever. It turned out that
>>> it didn't work at all, silently filling with garbage the List, and I was
>>> forced to move all code related to the StringList in the main thread, with a
>>> slight overhead which, IMO should not have been necessary. I couldn't
>>> understand if it was a Kylix bug or a feature.
>>>
>>> How would Lazarus behave with respect to this scenario? The scheme I
>>> described is expected to work?
>>
>> No. You should use a TMultiReadExclusiveWriteSynchronizer object to
>> synchronize access to your object, or use a critical section.
>
> Ehm, he made sure that only one thread accesses the TStringList at a
> time.

To me, this is not obvious from his mail ?

If the main thread only starts work after the secondary thread is done,
there should be no problem.

Michael.