Re: [fpc-devel] FCL Thread-safety
In our previous episode, Burkhard Carstens said: (implemented as TThread descendants if it matters) with no syncronization/serialization whatsoever. Can I be sure that such components will not interfere each other implicitely (somewhere deep inside the FCL)? No, you can't be sure. E.g. the fcl-xml stuff in latest released fpc-2.4.0 is *not* thread-safe, because it uses avl-tree which is not thread-safe. See http://mantis.freepascal.org/view.php?id=12984 and note: This bug is marked as fixed in 2.4.0 which is (partly) wrong. Avltree is fixed in 2.4.0 (you can set an own manager), and that is what the report is about (see title: Patch : thread safe/non-safe avl_tree implementation ) XML is not fixed. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] FCL Thread-safety
Am Mittwoch, 27. Januar 2010 09:17 schrieb Marco van de Voort: In our previous episode, Burkhard Carstens said: (implemented as TThread descendants if it matters) with no syncronization/serialization whatsoever. Can I be sure that such components will not interfere each other implicitely (somewhere deep inside the FCL)? No, you can't be sure. E.g. the fcl-xml stuff in latest released fpc-2.4.0 is *not* thread-safe, because it uses avl-tree which is not thread-safe. See http://mantis.freepascal.org/view.php?id=12984 and note: This bug is marked as fixed in 2.4.0 which is (partly) wrong. Avltree is fixed in 2.4.0 (you can set an own manager), and that is what the report is about (see title: Patch : thread safe/non-safe avl_tree implementation ) XML is not fixed. Right, that's why I wrote (partly) wrong .. relation to xml was the main point in that bug report and your final note Solved now DOM no longer depends on avltree. together with fixed in 2.4.0 might give the impression, XML is fixed in 2.4.0 .. regards Burkhard ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re[2]: [fpc-devel] FCL Thread-safety
Hello Nikolai, Wednesday, January 27, 2010, 8:36:53 AM, you wrote: NZ Luckily, I will not use any xml stuff yet. NZ However, verifying all of the components that my program might (also NZ implicitely) link to is quite a hard task... And it is very possible to NZ make a mistake, thinking that the code is thread-safe while in fact it NZ is not. Obviuosly this will lead to a total nightmare then. I was hoping NZ someone can give an idea about thread-safety in FCL (other than xml) in NZ general. Which is the meaning of Thread Safe for you ? Same object in two threads or same object instance in two threads ? For the second one, most objects are NOT thread safe, but for the first one most objects are thread safe as far as I know. -- Best regards, JoshyFun ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] FCL Thread-safety
I can confirm FCL-XML is thread safe, at least in FPC 2.5.1, also Zeos as far as you create a new connection to the database inside each thread. I'm using both libraries in a multithreaded daemon that receives an XML file via socket, then connects to a Postgres database using Zeos. While developing this, the first issue was many database deadlocks, and transaction problems caused because I was sharing a global database connection, the solution was creating an instance of the database connector in the Thread constructor, and destroy it in the Thread destructror. Regarding the FCL-XML, I was using an old version based on AVLTree, and found it have many problems when working within threads, all of them solved after upgrading to the latest version. Leonardo M. Ramé http://leonardorame.blogspot.com --- On Tue, 1/26/10, Nikolai Zhubr zh...@mail.ru wrote: From: Nikolai Zhubr zh...@mail.ru Subject: [fpc-devel] FCL Thread-safety To: fpc-devel@lists.freepascal.org Date: Tuesday, January 26, 2010, 11:08 PM Hello people, Is FCL thread-safe? To be more precise, what I mean is the following. I'm going to create 2 (or more) components so that they are completely unrelated to each other in _my_ code and use them separately within different threads (implemented as TThread descendants if it matters) with no syncronization/serialization whatsoever. Can I be sure that such components will not interfere each other implicitely (somewhere deep inside the FCL)? And just in case someone knows, will zeoslib components be thread-safe in the same sense? From a brief look, zeoslib doesn't use global variables too much, so I suppose zeoslib thread-safety mostly depends on the FCL thread-safety. (Except that zeoslib's internal library loader seems definitely not thread-safe, but this is no problem because normally it should only be used once at the very beginning) Thank you! Nikolai ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] FCL Thread-safety
27.01.2010 13:59, JoshyFun пишет: Hello Nikolai, Wednesday, January 27, 2010, 8:36:53 AM, you wrote: NZ Luckily, I will not use any xml stuff yet. NZ However, verifying all of the components that my program might (also NZ implicitely) link to is quite a hard task... And it is very possible to NZ make a mistake, thinking that the code is thread-safe while in fact it NZ is not. Obviuosly this will lead to a total nightmare then. I was hoping NZ someone can give an idea about thread-safety in FCL (other than xml) in NZ general. Which is the meaning of Thread Safe for you ? Same object in two threads or same object instance in two threads ? The first one. (I described my scenario a bit more specifically in my initial post of this thread) Nikolai For the second one, most objects are NOT thread safe, but for the first one most objects are thread safe as far as I know. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] FCL Thread-safety
27.01.2010 15:30, Leonardo M. Ramé: I can confirm FCL-XML is thread safe, at least in FPC 2.5.1, also Zeos as far as you create a new connection to the database inside each thread. I'm using both libraries in a multithreaded daemon that receives an XML file via socket, then connects to a Postgres database using Zeos. Thank you very much! That is very similar to what I'll be doing, except that I just dont use XML. Yes, I'll create 1 connector per thread of course. The only concern then is how to ensure that thread-safety is not (ocasionally) destroyed with some future FCL and/or zeoslib versions. It somehow seems quite uneasy to design a simple and yet reliable regression-test for automated testing. On the other hand, verifying it all by hand is also not what I'd be dreaming of. Thank you! Nikolai While developing this, the first issue was many database deadlocks, and transaction problems caused because I was sharing a global database connection, the solution was creating an instance of the database connector in the Thread constructor, and destroy it in the Thread destructror. Regarding the FCL-XML, I was using an old version based on AVLTree, and found it have many problems when working within threads, all of them solved after upgrading to the latest version. Leonardo M. Ramé http://leonardorame.blogspot.com ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] FCL Thread-safety
Well, I had to create a simple testing application that generates random XML messages and stress-test the daemon. About Zeos, my app does not compiles against the svn version, but a copy of an approved (by me!) version. Every couple of months, I get the latest version, then compile and test, if this works ok, I copy the whole directory of Zeos and place it in my app's dir tree, this tree is a frozen version of Zeos. This way, I'm not concerned about changes in the libraries. Leonardo M. Ramé http://leonardorame.blogspot.com --- On Wed, 1/27/10, Nikolai Zhubr zh...@mail.ru wrote: From: Nikolai Zhubr zh...@mail.ru Subject: Re: [fpc-devel] FCL Thread-safety To: fpc-devel@lists.freepascal.org Date: Wednesday, January 27, 2010, 12:27 PM 27.01.2010 15:30, Leonardo M. Ramé: I can confirm FCL-XML is thread safe, at least in FPC 2.5.1, also Zeos as far as you create a new connection to the database inside each thread. I'm using both libraries in a multithreaded daemon that receives an XML file via socket, then connects to a Postgres database using Zeos. Thank you very much! That is very similar to what I'll be doing, except that I just dont use XML. Yes, I'll create 1 connector per thread of course. The only concern then is how to ensure that thread-safety is not (ocasionally) destroyed with some future FCL and/or zeoslib versions. It somehow seems quite uneasy to design a simple and yet reliable regression-test for automated testing. On the other hand, verifying it all by hand is also not what I'd be dreaming of. Thank you! Nikolai While developing this, the first issue was many database deadlocks, and transaction problems caused because I was sharing a global database connection, the solution was creating an instance of the database connector in the Thread constructor, and destroy it in the Thread destructror. Regarding the FCL-XML, I was using an old version based on AVLTree, and found it have many problems when working within threads, all of them solved after upgrading to the latest version. Leonardo M. Ramé http://leonardorame.blogspot.com ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] FCL Thread-safety
27.01.2010 17:49, Leonardo M. Ramé: Well, I had to create a simple testing application that generates random XML messages and stress-test the daemon. About Zeos, my app does not compiles against the svn version, but a copy of an approved (by me!) version. Every couple of months, I get the latest version, then compile and test, if this works ok, I copy the whole directory of Zeos and place it in my app's dir tree, this tree is a frozen version of Zeos. This way, I'm not concerned about changes in the libraries. Yeah, I see. I'll probably have to work out some similar approach. Nikolai Leonardo M. Ramé http://leonardorame.blogspot.com ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Semicolon before else
On Tue, Jan 26, 2010 at 07:42, Graeme Geldenhuys graemeg.li...@gmail.com wrote: As for the 'otherwise' syntax. You are correct, I have never heard or seen it before. :-) But it is documented in the FPC Language Reference section 10.2.2. On more probably less known reserved identifier is FAIL. You can use it only inside constructor to indicate that object creation should actually fail and retur nil - meaning that you don't need some factory or creation helper function for those situations. Pretty useful, isn't it? :-) ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
