September 2004 - Boost-users

Comiling Boost with VC++.net
by Andreas Kempf 08 Sep '04

08 Sep '04

My IDE for C++ is VC++.net I heard that it is impossible to compile Boost with its compiler. I replaced the compiler with the VC++.net 2003 Toolkit Compiler, but it still doesn't work. Can anyone help me compiling with the VC++.net 2003 Toolkit?

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RE: [Boost-users] signal slot flexibility
by Frank Maddin 08 Sep '04

08 Sep '04

Ahh, so now I'm able to do such things as this. Hello* h_ptr = new Hello(); World* w_ptr = new World(); typedef boost::signal< int (int, float) > IntFloatSignal; IntFloatSignal sig; sig.connect(boost::bind(&Hello::alternate_int_float, h_ptr, _1, _2)); sig.connect(boost::bind(&World::alternate_int_float, w_ptr, _1, _2)); float temp = 0.0f; sig(1, temp); > I don't see much benefit to extra (explicit) level of indirection here. > Most slots are short bind expressions that don't ever need to be > revisited, so it seems that it could be a bit challenging to determine > where some slots should reside: always in the class containing the > member function that is called (assuming one only uses member > functions!)? I guess I was thinking that since nothing is done with inheritance, it provides less opportunity to do things that might get you into trouble. If I've a hierarchy that looks something like this: BaseObject SimpleObject : BaseObject, signals::trackable ComplexObject : SimpleObject ReallyComplexObject : ComplexObject, signals::trackable where a SimpleObject can get a signal of one type and a ReallyComplexObject object can get another, is trackable inheritance ok with this or is there some other recommended method? Thanks again, Frank -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Doug Gregor Sent: Tuesday, September 07, 2004 2:38 PM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] signal slot flexibility On Sep 7, 2004, at 1:36 PM, Frank Maddin wrote: > If I add a function to both Hello and World, from the "Hello World" > example, called alternate() and set up signals like so: > > > > boost::signal<void (Hello*) > sig_h; > > boost::signal< void (World*) > sig_w; > > > > sig_h.connect(boost::mem_fn(&Hello::alternate)); > > sig_w.connect(boost::mem_fn(&World::alternate)); > > > > I have to define two different signals since the object type is part > of the signal definition. Is there an easy way to get a single signal > to call the alternate() function of both Hello and World? Without Hello and World being related (e.g., sharing a base class declaring a virtual "alternate" function), I don't see a way. Still, when you call these signals you have to know whether you have a "Hello" in hand or a "World"; perhaps you wanted to store the "Hello" and "World" objects within the signal, and pass it no arguments? For instance, boost::signal<void()> sig; sig.connect(boost::bind(&Hello::alternate, &my_hello)); sig.connect(boost::bind(&World::alternate, &my_world)); > I recently found this signal slot solution. > http://www.codeproject.com/cpp/ElmueSignalsandSlots.asp > > There is an extra level of indirection here, in that you define a slot > that points to the function. I'd be interested to see what people on > this forum think about this solution. If I understand things > correctly, this solution doesn't seem to fit into the categories > listed in the "Choice of Slot Definitions" docs. I don't see much benefit to extra (explicit) level of indirection here. Most slots are short bind expressions that don't ever need to be revisited, so it seems that it could be a bit challenging to determine where some slots should reside: always in the class containing the member function that is called (assuming one only uses member functions!)? > Also a general signal slot question. What are the main reasons why > developers don't use an inherited pure interface for every callback > type? A signal would be a template class with a list of pointers to > the interface and some methods to operate on the list. Not flexible > enough? You often want only one event out of five, so it's a pain to drop in all of the stubs needed to ignore the other events. Also, you don't get a choice of names to use: if the writer of the interface says it's "on_click", you must write a function named "on_click" even though you'd rather write something like "submit_current_query" that describes the action taken when the event fires, not the event itself (which is essentially irrelevant). > Doesn't scale well to larger uses? Time spent calling virtual > functions? I saw this in the boost signal docs that might apply - > "the use of a large number of small adaptor classes containing virtual > functions has been found to cause an unacceptable increase in the size > of executables (polymorphic class types require more code than > non-polymorphic types)". This is more of an implementation detail; using function pointers instead of virtual functions tends to reduce the amount of code generated for libraries such as Boost.Signals or Boost.Function. Doug _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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signal slot flexibility
by Frank Maddin 07 Sep '04

07 Sep '04

Hi, I have some questions about signals. If I add a function to both Hello and World, from the "Hello World" example, called alternate() and set up signals like so: boost::signal<void (Hello*) > sig_h; boost::signal< void (World*) > sig_w; sig_h.connect(boost::mem_fn(&Hello::alternate)); sig_w.connect(boost::mem_fn(&World::alternate)); I have to define two different signals since the object type is part of the signal definition. Is there an easy way to get a single signal to call the alternate() function of both Hello and World? I recently found this signal slot solution. http://www.codeproject.com/cpp/ElmueSignalsandSlots.asp There is an extra level of indirection here, in that you define a slot that points to the function. I'd be interested to see what people on this forum think about this solution. If I understand things correctly, this solution doesn't seem to fit into the categories listed in the "Choice of Slot Definitions" docs. Also a general signal slot question. What are the main reasons why developers don't use an inherited pure interface for every callback type? A signal would be a template class with a list of pointers to the interface and some methods to operate on the list. Not flexible enough? Doesn't scale well to larger uses? Time spent calling virtual functions? I saw this in the boost signal docs that might apply - "the use of a large number of small adaptor classes containing virtual functions has been found to cause an unacceptable increase in the size of executables (polymorphic class types require more code than non-polymorphic types)". Thanks Frank

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Re: [Boost-users] bjam with mingw
by Brewer, Christopher 07 Sep '04

07 Sep '04

Angus- I had similar problems with bjam under MinGW. By experimentation, I discovered that I could make bjam work under MinGW by moving it from it's previous location at 'c:/msys/1.0/bin' to 'c:/msys/1.0/mingw/bin'. FYI, you can find this thread starting at Boost-users Digest, Vol 250, Issue 1, and ending (successully :) at Boost-users Digest, Vol 253, Issue 1. HTH, Chris Brewer

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bjam with mingw
by Angus Leeming 07 Sep '04

07 Sep '04

Please forgive the newbie questions, but I am trying and failing to build boost with MinGW. I've grabbed the CVS sources of boost from the sourceforge anonymous mirror. I've installed MinGW and MinSYS. The MinGW tools are in my path. From the MinSYS console: $ cd ~/boostcvs $ which which c++ /mingw/bin/c++ $ c++ --version c++.exe (GCC) 3.2.3 (mingw special 20030504-1) Just to check that the tools are working: $ cd libs/spirit/phoenix/test $ c++ -I$HOME/boostcvs -o new_test new_test.cpp $ ./new_test /////////////////////////////////////////////////////////////////////////////// Tests concluded SUCCESS!!! /////////////////////////////////////////////////////////////////////////////// Now trying to do something similar using bjam: $ cd ~/boostcvs/libs/test/build $ bjam '-sTOOLS=mgw' CALL "C:\Program Files\Microsoft Visual Studio .NET 2003\VC7\bin\VCVARS32.BAT" >nul "C:\Program Files\Microsoft Visual Studio .NET 2003\VC7\bin\cl" /Zm800 -nologo /EHsc -c -DBOOST_TEST_NO_AUTO_LINK=1 /Z7 /Od /Ob0 /EHsc /GR /MTd /Op /Zc:forScope /Zc:wchar_t -I"..\..\..\bin\boost\libs\test\build" -I"d:\MinSYS\1.0\home\Angus\boost_cvs" -Fo"..\..\..\bin\boost\libs\test\build\libboost_unit_test_framework.lib\vc7.1\debug\runtime-link-static\threading-multi\unit_test_main.obj" -Tp"d:\MinSYS\1.0\home\Angus\boost_cvs\libs\test\build\../src/unit_test_main.cpp" ...failed vc-C++ ..\..\..\bin\boost\libs\test\build\libboost_unit_test_framework.lib\vc7.1\debug\runtime-link-static\threading-multi\unit_test_main.obj... vc-C++ ..\..\..\bin\boost\libs\test\build\libboost_unit_test_framework.lib\vc7.1\debug\runtime-link-static\threading-multi\supplied_log_formatters.obj The system cannot find the path specified. The system cannot find the path specified. [ snip all other, similar messages ] For the life of me I can't see why bjam is trying to build the VC++ target. I can't even run $ bjam --help because it just does the same thing, trying and failing to build stuff with VC++. I have also tried running from the top level boost directory and with the '-sMINGW_ROOT_DIRECTORY=/d/mingw' command line option to bjam, all to no avail. (From my understanding of the docs at http://www.boost.org/tools/build/v1/mingw-tools.html, that shouldn't be necessary.) I have changed the TOOLS name to 'mingw' rather than 'mgw'. Again , no dice. Finally, in desperation, opening up a DOS prompt and repeating the exercise. Nope. Same result. Can anyone help me out? Regards, Angus

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RE: [Boost-users] output stream cloning?
by Ben Hutchings 07 Sep '04

07 Sep '04

Jon Biggar <jon(a)levanta.com> wrote: > Is there any package in Boost (or upcoming in the Boost review queue) > that would let me create an output stream that clones its output to > one or more underlying output streams? Jonathan Turkanis's Iostream library, which is currently under review and has been mostly positively received, seems to make it pretty trivial to write such a thing - see <http://lists.boost.org/MailArchives/boost/msg69799.php> and <http://lists.boost.org/MailArchives/boost/msg69827.php>.

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problem with CVS Boost.Python with MSVC
by Stephen D Evans 07 Sep '04

07 Sep '04

The CVS change to boost/boost/python/detail/prefix.hpp from revision 1.3 to 1.4 has obviated the effect of boost/boost/python/detail/wrap_python.hpp in _DEBUG when compiling with MSVC. Python now forces the debug library as if BOOST_DEBUG_PYTHON is permanently in effect. Revision 1.3 does not exhibit this problem. The added #include <pyconfig.h> is the cause. Stephen D Evans

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dangerous use of boost::bind
by Gast 128 07 Sep '04

07 Sep '04

Dear all, In my work I use the boost libraries quite frequently, especially boost::bind to create function objects. However its use is not as transparent as I hoped for. Especially using functions in boost bind with signatures returning const& can give unpredictable results. For example: struct KX { KX (int i); //etc. }; typedef std::pair<int, KX> pair_t; pair_t do_kx_pair(int i) { return std::make_pair(i, KX(i)); } //following will go wrong: KX x = boost::bind(&pair_t::second, boost::bind(&do_kx_pair, i))(); The last line compiles on Visual .NET 2003 without any warning (even on level 4). However after spending two days in boost bind source code, I could see that it actually returns const& to a temporary created by boost bind. The reason for this is that arguments are copied by value, and thus functions with const & (or in this case pointer to member) can return then const & from temporaries. Is there no way that at least boost::bind could issue a compiler warning? Because now I have to think deep before I create a nested boost bind construction. For example the following construction is not wrong; the const & is again taken from a temporary which boost::bind holds, but this is destroyed after the expression: KX x = boost::bind(&pair_t::second, do_kx_pair(i))(); If this is not solvable, perhaps it's a good idea to include this case in the documentation. Wkr, me (btw boost::bind is a great improvement over the std::mem_fun and std::bind1st etc.)

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Problems with boost::format and Visual C++ 7.0
by Tom Quarendon 07 Sep '04

07 Sep '04

I have trouble compiling code that makes use of the boost::format library. In particular I get compile errors from basic_format::operator= method (line 90 format_implementation.hpp). If I change the body to look like if(this == &x) return *this; basic_format<Ch, Tr> x1(x); // These 2 lines used x1.swap(*this); // to be 1 return *this; It compiles. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com) Version: 6.0.737 / Virus Database: 491 - Release Date: 11/08/2004

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output stream cloning?
by Jon Biggar 07 Sep '04

07 Sep '04

Is there any package in Boost (or upcoming in the Boost review queue) that would let me create an output stream that clones its output to one or more underlying output streams? -- Jon Biggar Levanta Inc jon(a)levanta.com

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