April 2009 - Boost-users - lists.preview.boost.org

[mpl] register types in a mpl sequence type
by Thomas Lemm 09 Apr '09

09 Apr '09

All, I am trying to accomplish a compile time type registry by trying to register a specific subset of my classes into an mpl sequence type. So during compilation that sequence type should hold a sequence of my classes for subsequent processing (e.g. by mpl::for_each). An example: --- code start -------------- class Super { tyedef mpl::list<> SubTypesList; // usage of SubTypesList: printSubtypes() { mpl::for_each< SubTypesList >( ... )}; }; class A : public RegisterWith< A, Super > {}; class B : public RegisterWith< B, Super > {}; --- code end -------------- now Super::SubTypesList should be equivalent to mpl::list< A, B >. I have the feeling that this approach is not achievable with templates alone due to the C++ template mechanism not being able to redefine a type. Still I would be happy being proven wrong. Any pointers to similiar problems and solutions, alternative approaches (maybe using the boost_pp?) are welcome, too. Kind regards Thomas Lemm

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Re: [Boost-users] Linking with dynamic boost thread library
by John Wilkinson 09 Apr '09

09 Apr '09

> If the program compiles and runs the same only based on whether boost*.lib > is there, what function does the boost*.dll serve The boost*.lib files, as I think someone said earlier, are the import libraries for the boost*.dll run-time libraries. These are what you link to, in order to use boost*.dll at run time. The DLL files do not need to be in the link path, only in the executable path when your program is run. The boost*.lib files need to be in the link path when you build your program. John

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[lambda] how to get rid of the reference argument in lambda functor?
by Pobinger Gerhard Stefan 09 Apr '09

09 Apr '09

Hi *, I was desparately trying to compile something like this (VS2008), always getting the error that it cannot convert from int* to int*&. :boost::shared_ptr<int> c; ::boost::lambda::var(c) =::boost::lambda::constructor <::boost::shared_ptr<int>>() (::boost::lambda::new_ptr<int>()() ) [This is "short form" for the conventional code ::boost::shared_ptr<int>c=::boost::shared_ptr<int>(new int());] (1) The reason is that all lambda functors take arguments by reference. In this case, make_const in front of shared_ptr did not solve the problem, it causes immediate evaluation of the new_ptr functor... Is there any way to rewrite this (1) short line of code in boost-lambda? /Gerhard Pobinger

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Re: [Boost-users] Linking with dynamic boost thread library
by Steven Watanabe 09 Apr '09

09 Apr '09

AMDG Green, Jason M NSWCDL, W33 wrote: > I have a directory in my project call Boost. I added the directory to the > library files list. > In this directory I have the libboost*.lib files and the boost*.dll files. > I am able to get it working with no problem if I only have the libboost*.lib > files in there. If I rename them, and add the dll into the directory, it > will not build. That is where it will give me the error saying that it is > looking for libboost*.lib > Whoa. I'm confused. Is the linker complaining about libboost*.lib or boost*.lib? If you define BOOST_ALL_DYN_LINK or BOOST_<library name>_DYN_LINK the compiler will look for the import libraries for the dlls. > Green, Jason M NSWCDL, W33 wrote: > >> the compile warns me that it "cannot open file >> 'boost_regex-vc80-mt-gd-1_38.lib'" >> >> In Christ, Steven Watanabe

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[interprocess] warning C4251: need dll-interface
by Brent Arias 09 Apr '09

09 Apr '09

I've defined a class to use within shared memory, and I've decorated it with a Windows _declspec(export) to expose it from a DLL. When I compiled with VC 2008, I got this warning: Warning C4251: class 'boost::interprocess::vector<T,A>' needs to have dll-interface to be used by clients of 'MyClass' I searched boost user archives for any discussion of this, and in the context of boost.signals I've seen someone comment to simply disable the warning with: #pragma warning (disable: 4251) Std::list<OtherClass*> talkers; #pragma warning (default: 4151) Does this also apply to boost.interprocess? Is it really safe to ignore this warning and continue to use the interprocess code from within a DLL? Brent Arias

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Concept DefaultConstructible vs type traits has_trivial_constructor
by Hicham Mouline 09 Apr '09

09 Apr '09

Hi, What is the difference between the 2? For a type T, can it be DefaultConstructible and has_trivial_constructor<T> is false? Rds,

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Re: [Boost-users] boost build interface
by Rudolf Leitgeb 09 Apr '09

09 Apr '09

FWIW this doesn't have to be a windows only GUI. We could use the QT widget set and make this portable to most platforms supported by boost. Note, that Qt is LGPL now, so you could even include this into commercial distributions if needed. Am 08.04.2009 um 16:10 schrieb Green, Jason M NSWCDL, W33: > Not that I am volunteering, but it isn't that hard to come up with a > simple > dialog based mfc project that would set up the commands to properly > run the > boost build.

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[interprocess] placement new allocator for vector
by Brent Arias 09 Apr '09

09 Apr '09

I'd like to have a user type that contains a vector and yet is still binary serializable, *AND* that can be used entirely inside or outside of shared memory. My idea is to give the vector a placement new allocator, it goes like this: class MyBinarySerialType { struct SomeItem { char first[10]; char second[10]; }; SomeItem m_Items[16]; //The placement new allocator points with an offset_ptr<SomeItem> //to the location &m_Items[0] boost::interprocess::vector<SomeItem, /*placement new allocator*/> m_vItems; public: MyBinarySerialType(const /*placement new allocator*/ &alloc); } I'd like to know if interprocess allocators can already do this for me (via template params, etc) or if I need to write my own allocator. If this is done correctly, I think it means I can "new" MyBinarySerialType from the regular heap and it will work entirely outside of shared memory. Likewise if I use segment.construct<MyBinarySerialType>()(...), then the whole thing should be created inside of shared memory. Either way, the vector will allocate strictly to a piece of memory inside the size of the class. Brent Arias

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[date_time] Time duration parsing
by Konstantin Litvinenko 09 Apr '09

09 Apr '09

Hi All! I have a string "14:34" and want to parse it into boost::posix_time::time_duration. How can I do that?

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[serialization] Export question
by Tom Aylesworth 09 Apr '09

09 Apr '09

I just want to make sure that I understand the use of the Serialization library's EXPORT macros. On the "Serializable Concepts" page of the documentation, it states: -- The macro BOOST_CLASS_EXPORT_GUID associates a string literal with a class. ... This permits each class to be in a separate header file along with its string identifier. -- However, on the "Special Considerations" page, I find: -- Note that the implementation of this functionality requires that the BOOST_CLASS_EXPORT macro appear after and the inclusion of any archive class headers for which code is to be instantiated. ... Note that including BOOST_CLASS_EXPORT in the "a.hpp" header itself as one would do with other serialization traits will make it difficult or impossible to follow the rule above regarding inclusion of archive headers before BOOST_CLASS_EXPORT is invoked. This is different than other serialization traits which would normally be included in same file as the class declaration. -- The associated example shows the EXPORT macro following the #include of the header defining the class to be exported. I would certainly much rather have the EXPORT macros appear in the header with the class that defines them. I take it that means I have to guarantee that the file actually responsible for operating on an archive includes my headers with the class definitions and EXPORT macros *after* including the appropriate archive headers (e.g., "boost/archive/xml_oarchive.hpp"). Is that correct? Are there any other gotchas I should be aware of if I place the EXPORT macros in the headers with the classes to be exported? Thanks, Thomas Aylesworth Senior Software Engineer Reality Mobile

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