March 2006 - Boost-users - lists.preview.boost.org

Re: [Boost-users] enable_shared_from_this - or an alternative..
by Nat Goodspeed 21 Mar '06

21 Mar '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of James Hughes > Sent: Monday, March 20, 2006 11:29 AM > To: 'boost-users(a)lists.boost.org' > Subject: Re: [Boost-users] enable_shared_from_this - or an alternative.. > > > >I have a couple of classes that I want to self register > > themselves with a > > >monitoring class. To do this they must pass a shared_ptr of > > themselves to > > >the monitor register function. > > > > > >Therefore I need to make a shared_ptr form the this pointer, in the > > >constructor. [Nat] We have a similar need: the base class registers in a central registry; we have many subclasses of the base class. We use dumb base* pointers for this purpose. We can get away with that because, just as the base-class constructor registers each instance, so the base-class virtual destructor unregisters the instance. Indeed, for our purposes, we don't WANT smart pointers in the registry. If the last smart-pointer reference to a heap object goes away, we don't want the reference in the registry to make the instance immortal. In that case, the smart pointer to the heap object decrements the count to 0, the object is destroyed, and its destructor unregisters the instance. A side benefit is that we don't have to care whether the instance is static, auto or heap. Nor do we need factory functions.

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Support for Thread lib on MinGW?
by Matt England 20 Mar '06

20 Mar '06

Will Boost ever support the Thread library for mingw? As per http://boost.org/more/getting_started.html#auto-link : " <libthread>: For technical reasons static linking is supported on only one Windows compiler (Visual C++). " -Matt

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System call to get current process memory usage?
by Matt England 20 Mar '06

20 Mar '06

What if any system calls exist to get the current process' system memory usage (including all of the current process' threads)? I'm trying to write unit tests to make sure that my memory allocation processes (for Boost "smart pointers) are actually deallocating correctly after thousands of dynamic allocations...and my presumption is that a process-memory "self check" thoughout this process will be very useful for my self-running unit test. I'd prefer cross-platform calls (be it POSIX, unix/linux, Boost C++, etc...preferably not win32-specific if I can avoid it, but if I must I will) if I can get them, but I'll take a system specific all (for my testing prototype) if I must. Thanks for any help, -Matt

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how to use shared_ptr to wrap std::vector and return from function?
by kdsfinger＠gmail.com 20 Mar '06

20 Mar '06

hi, Boost users Suppose I created a large data in a function and want to return it back to where the function was called. I want to return the pointer so that the deep copy of the large data is not needed and memory leak is nicely handled. Can someone let me know how to do it? Here is something come up in my mind: boost::shared_ptr< std::vector<int> > getV(){ boost::shared_ptr< std::vector<int> > v; v->push_back(1); v->push_back(2); // bla bla bla return v; } int main(){ boost::shared_ptr< std::vector<int> > v = getV(); std::cout << v->at(0); return 0; } I got the following message when run the program: /usr/include/boost/shared_ptr.hpp:253: T* boost::shared_ptr<T>::operator->() const [with T = std::vector<int, std::allocator<int> >]: Assertion `px != 0' failed. Aborted How can I get it correct? Is there any deep copy when the getV() return the shared_ptr? Thanks a lot. zl2k

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Re: [Boost-users] enable_shared_from_this - or an alternative..
by James Hughes 20 Mar '06

20 Mar '06

> -----Original Message----- > From: Alan M. Carroll [mailto:amc@network-geographics.com] > Sent: 20 March 2006 13:44 > To: boost-users(a)lists.boost.org > Cc: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] enable_shared_from_this - or an > alternative.. > > > At 04:13 AM 3/20/2006, James Hughes wrote: > >Hello All, > > > >I have a couple of classes that I want to self register > themselves with a > >monitoring class. To do this they must pass a shared_ptr of > themselves to > >the monitor register function. > > > >Therefore I need to make a shared_ptr form the this pointer, in the > >constructor. > > Why not use intrusive_ptr? Way back when, I wrote my own > equivalent of that instead of using Boost.shared_ptr partly > for this very reason (i.e., having to use smart pointers in > constructors). > Ah, just read my Boost book on intrusive pointers and I think they would work. Not sure I will use for current issues, as have now written code for a factory mechanism (which appears to work!), but certainly worth knowing for the future. Thanks Rgds James

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Unicode support
by Calderon Hector 20 Mar '06

20 Mar '06

Is there any rationale for not supporting Unicode in some boost libraries (e.g. filesystem, program_options)? ++Hector C. ---------------------------------- --------------------------------- Yahoo! Mail Use Photomail to share photos without annoying attachments.

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Re: [Boost-users] enable_shared_from_this - or an alternative..
by James Hughes 20 Mar '06

20 Mar '06

> > > >> > > _______________________________________________ > > Boost-users mailing list > > Boost-users(a)lists.boost.org > > http://lists.boost.org/mailman/listinfo.cgi/boost-users > > > is the following snipped what you have in mind? > > struct base {}; > struct derived1 : public base {}; > struct derived2 : public derived1 {}; > > typedef boost::shared_ptr<base> base_ptr; > > struct monitor > { > void > add( const base_ptr & _ptr) > { > // ... > } > }; > > struct factory > { > factory( monitor & _monitor ) : > monitor_(_monitor) > { > } > > template<typename T> > boost::shared_ptr<T> > create( void ) > { > boost::shared_ptr<T> tmp(new T); > monitor_.add(tmp); > return tmp; > } > > private: > monitor & monitor_; > }; > > void > foo( void ) > { > monitor m; > factory f(m); > f.create<derived1>(); > f.create<derived2>(); > } > > -- dave > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users > Hi Dave, Yes, I think that pretty much does exactly what I require. And gives me a (almost comnpletely) generic factory class to boot! Thanks very much! James

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bjam and Intel 8 on windows
by Andreas Fabri 20 Mar '06

20 Mar '06

Hello, I just tried to install boost for the Intel 8 Compiler. bjam.exe "-sTOOLS=intel-win32" install failed updating 948 targets... skipped 412 targets... updated 3323 targets... Didn't I choose the right toolset? If I only want to create program_options, is this the right command: bjam.exe "-sTOOLS=intel-win32 --with-program_options" install thanks in advance, andreas

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Re: [Boost-users] enable_shared_from_this - or an alternative..
by Alan M. Carroll 20 Mar '06

20 Mar '06

At 04:13 AM 3/20/2006, James Hughes wrote: >Hello All, > >I have a couple of classes that I want to self register themselves with a >monitoring class. To do this they must pass a shared_ptr of themselves to >the monitor register function. > >Therefore I need to make a shared_ptr form the this pointer, in the >constructor. Why not use intrusive_ptr? Way back when, I wrote my own equivalent of that instead of using Boost.shared_ptr partly for this very reason (i.e., having to use smart pointers in constructors).

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Re: [Boost-users] enable_shared_from_this - or an alternative..
by David Klein 20 Mar '06

20 Mar '06

boost-users-bounces(a)lists.boost.org wrote: >> -----Original Message----- >> From: David Klein [mailto:d.klein@ascaron.com] >> Sent: 20 March 2006 10:27 >> To: boost-users(a)lists.boost.org >> Subject: Re: [Boost-users] enable_shared_from_this - or an >> alternative.. >>> [snip] > > Thanks Dave, that does cover the problem well. > > However, I cannot use the null deleter mechanism suggested as the > shared_ptr is passed on to monitor and is used there. The second > scheme, using a factory fucntion, would seem to be approriate, > however, how to I handle creation when the CSource1 class is actually > to be used as a base class? If the factory function is in CSource1, > it doesnt know about any derived classes. I don't want to have to > write factory functions in every dervied class - that seems a waste. > Is there a correct technique for getting around this issue? I am > assuming a template of some description, but now sure what that > entails. > > > > > James > >> > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users is the following snipped what you have in mind? struct base {}; struct derived1 : public base {}; struct derived2 : public derived1 {}; typedef boost::shared_ptr<base> base_ptr; struct monitor { void add( const base_ptr & _ptr) { // ... } }; struct factory { factory( monitor & _monitor ) : monitor_(_monitor) { } template<typename T> boost::shared_ptr<T> create( void ) { boost::shared_ptr<T> tmp(new T); monitor_.add(tmp); return tmp; } private: monitor & monitor_; }; void foo( void ) { monitor m; factory f(m); f.create<derived1>(); f.create<derived2>(); } -- dave

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