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[serialization] warnings while building Boost.Serialization
by Christoph Ludwig 19 Oct '04

19 Oct '04

Hi, when building Boost.Serialization my compiler (gcc 3.4.2 on i686-pc-linux-gnu) issues some warnings. They are no big deal for me, but I think they can (and should) easiliy be avoided. * In wchar_from_mb.hpp, line 107, we have for(int i = 0; i++ < MB_CUR_MAX;){ //... On my system, MB_CUR_MAX evaluates to an expression of type size_t, whence the compiler warns about a comparison between signed and unsigned. I don't know which type MB_CUR_MAX is supposed to have according to the relevant standards, but I think it is safe to assume that the value of MB_CUR_MAX will always fit into a signed int. I therefore propose to change above line into: for(int i = 0; i++ < int(MB_CUR_MAX);){ //... * In basic_xml_archive, line 38, I get a warning about a potentially uninitialized variable msg: virtual const char *what( ) const throw( ) { const char *msg; switch(code){ case xml_archive_parsing_error: msg = "unrecognized XML syntax"; break; case xml_archive_tag_mismatch: msg = "XML start/end tag mismatch"; break; default: archive_exception::what(); // (*) } return msg; } I think the compiler caught a genuine mistake and the line marked (*) should read msg = archive_exception::what(); Regards Christoph -- http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/cludwig.html LiDIA: http://www.informatik.tu-darmstadt.de/TI/LiDIA/Welcome.html

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[signals]
by Roland Schwarz 19 Oct '04

19 Oct '04

I wonder if it is possible to use the signal library to do interprocess/(synchronized)interthread calls. Would it be easily possible to extend it into this aerea if not already possible? Am I considering the wrong library? If yes, could anyone please suggest a better approach? Thanks, Roland

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RE: [boost] Re: Library Proposal: database (boost::db)
by Brian Braatz 19 Oct '04

19 Oct '04

> On Behalf Of Michael van der Westhuizen > >> > >>Can you compae it with Database Template Library > >>http://dtemplatelib.sourceforge.net/index.htm > >>? > > > > > > Just an FYI here- I recently evaluated the DTL and it uses RTTI > > internally- > > Thoughts on OTL? > > http://otl.sourceforge.net/ > > I've used it a few times, and it's extremely capable. > > Michael Thanks for the link- that is very interesting. It looks like I can get what I need from it. IN rough comparison, it looks like the MYSQL++ library may be a bit more "normal" looking to DB developers who are used to disconnected recordsets, but it looks like the OTL libraries have far greater power. At the end of the day- I believe that a balance between "recordset"-ish model of MYSQL++ and the power of OTL would be a good combination. A library is not useful if it is too hard to get up to speed on OR too terribly different from what people are used to.

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Serialization - building shared libs
by Neal Becker 19 Oct '04

19 Oct '04

I brought up the topic that int the current cvs serialization libs are only built static, not shared. The reason for this is that the library uses this construct: ,----[ /home/nbecker/stuff/A.hpp ] | // {{{ struct A | | struct A { | int i; | A() { i = 1; } | static const A instance; | }; | | // }}} | | extern const A A::instance = A(); `---- If this is included into 2 shared libraries, will A::instance be shared? I have tested this on Linux. If you dlopen 2 different shared libs, it will work correctly, if you set the flags RTLD_NOW|RTLD_GLOBAL. Since this will work correctly on some systems, I would like to see this supported. It is impossible to use serialization with boost::python without shared libs.

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RE: [boost] Object Pool
by Abdullah Sowayan 18 Oct '04

18 Oct '04

Please ignore my prior question. I finally understood the whole process. Abdul -----Original Message----- From: Abdullah Sowayan Sent: Monday, October 18, 2004 11:53 AM To: boost(a)lists.boost.org Subject: [boost] Object Pool I am trying to use the Object Pool library. In the documentation I came across the following (html table): t.construct(???) ElementType * ElementType must have a constructor matching ???; the number of parameters given must not exceed what is supported through pool_construct <http://www.boost.org/libs/pool/doc/implementation/pool_construct.html> Allocates and initializes an object of type ElementType. If out of memory, returns 0. Amortized O(1). 1) What is "???" referring to? 2) What is I have the following class class A { public: A(int i, std::string s); ... }; How can I create a pool of As? Note that there isn't a constructor A::A( ) that takes nothing. How can I say that the pool for instance would initialize all objects to A::A(1, "Howdy") Thanks, Abdul _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

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Re:Re: [boost] Sprit-1.6 and latest boost
by Robert Ramey 18 Oct '04

18 Oct '04

Joel de Guzman wrote: > And thank you too for fixing all apply_if's and stuff in all spirit > related libraries in the boost CVS. And thanks for doing the same for the serialization library! Robert Ramey

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Object Pool
by Abdullah Sowayan 18 Oct '04

18 Oct '04

I am trying to use the Object Pool library. In the documentation I came across the following (html table): t.construct(???) ElementType * ElementType must have a constructor matching ???; the number of parameters given must not exceed what is supported through pool_construct <http://www.boost.org/libs/pool/doc/implementation/pool_construct.html> Allocates and initializes an object of type ElementType. If out of memory, returns 0. Amortized O(1). 1) What is "???" referring to? 2) What is I have the following class class A { public: A(int i, std::string s); ... }; How can I create a pool of As? Note that there isn't a constructor A::A( ) that takes nothing. How can I say that the pool for instance would initialize all objects to A::A(1, "Howdy") Thanks, Abdul

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boost::shared_ptr interface
by David M. Jones 18 Oct '04

18 Oct '04

I ran into a situation (see my "smart list" post on the boost users group) where I wanted to create a custom allocator whose pointer typedef is boost::shared_ptr. In other words, the code would look something like: template <typename T> class my_allocator { public: typedef boost::shared_ptr<T> pointer; }; The problem with doing this is that boost::shared_ptr<T> does not have the same "interface" as the equalivalent raw pointer type T*. (I use the term interface in the generic programming/template sense; not in the object oriented sense.) One example is that there is no operator= on boost::shared_ptr that takes a raw pointer; instead reset() must be used. Here are my questions: (1) What advantage does this change of interface serve that makes it worth breaking potential operations such as that above? (2) Does anyone have ideas on how to get around this problem? I toyed with the idea of writing a class that derives from boost::shared_ptr and has the interface that I desire -- anybody have thoughts on this? Thanks, David M. Jones

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explicit shared_ptr(weak_ptr<Y> const & r);
by John Torjo 18 Oct '04

18 Oct '04

Hi Peter, Just a thought: perhaps this constructor: explicit shared_ptr(weak_ptr<Y> const & r); should be private, and the only way to create a shared_ptr from a weak_ptr is: shared_ptr<T> val = weak->lock(); This way, the shared_ptr public constructors will never throw. Users will not make mistakes like this: shared_ptr<T> val = weak; I'm saying this, because I just made this mistake a few hours ago... After a while, the shared_ptr<> constructor started to throw at me ;) Best, John -- John Torjo, Contributing editor, C/C++ Users Journal -- "Win32 GUI Generics" -- generics & GUI do mix, after all -- http://www.torjo.com/win32gui/ -- v1.5 - tooltips at your fingertips (work for menus too!) + bitmap buttons (work for MessageBox too!) + tab dialogs, hyper links, lite html

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Re:[boost] Re: Re: Re: RTL status -"help wanted".
by Robert Ramey 18 Oct '04

18 Oct '04

FWIW - I love this idea !!!! I had forgotten about but when back and refreshed my memory. 1) its got nothing to do with being a wrapper to access a traditional database. That might be worthy project but this project isn't it. c) its all compile time. That means the the schemas can't be changed dynamically. This is inherent in the design. So its not a universal replacement for anything. However, I believe the time is now for such a library. Let me explain. Commmon use case. I am a freelance software developer. It often occurs that a customer has a situation which maps directly to a set of database schemas. The easiest way I've found to accomplish ths is (please - don't laugh) is to make a database in MS Access and write a VB program which peeks and pokes at it via ADO or something similar. This approach has the following features. a) Its simple to build and prototype the database. b) Its simple to fixit up when something changes. c) It eliminates a whole bunch of programming required to maintain data d) it eliminates a whole bunch of programming to query data. Just insert and test the query in Access. When it works, invoke the name of the query from VB - very easy. e) It depends on MS implementation of ADO which is very quirky in my opinion. f) It uses VB which will drive a real programmer crazy. g) Its all run time - no compile time optimization. h) Its all run time - no compile time checking. VB delays checking everything to the last possible moment - like when I'm home in bed. i) Its easy to make a nice UI that customer's love j) one doesn't have to worry about the size of things like history logs etc as its all handled by the DB. k) the data is accessible by other tools - basically and SQL query. So there is a class of applications which a) don't require that the schema changes after compilation b) need fast response c) use datasets of bounded size. Examples might be: a) address/contact manager for a palm computer/cell phone b) web database to support sales of tickets to grateful dead concerts as soon as they are announced. c) many small business databases - a years accounting. So I think this is interesting for what it is. I'm concerned that it might get bogged down by concerns that it isn't something else. In my view this sometimes occurs to boost proposals. I just looked over the documentation and I like what I see. Its no clear what's missing - of course I didn't try to use it. I think you might get more response to your request for help if. a) the directory structure and documentation looked more like a boost library so that one could just paste it into his boost tree. b) it was clear what's working and what's not. Maybe this should be reflected in the directory structure. c) If it was divided into working / not working. d) if the working subset was immediately useful. E.g. transactions could be postponed. It looks like you've focused on adding all the features before finishing off the basics ( documentation, examples, tests, etc.) This makes it hard for users to become addicted to your library which is what you need to get more help. The best way to get help is to get people using (part of) your library. When they need some feature, you can pressure them to create it and add a test. Machines and applications are now being made that can really benefit from the RTL library. Robert Ramey

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