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[python] converting C++ object to PyObject
by Johan Råde 05 Dec '11

05 Dec '11

I have three C++ classes X, Y and Z that I have exported from C++ to Python using python::class_. Now I want to write a factory function like PyObject* f(char c) { if(c == 'x') return new X; else if(c == 'y') return new Y; else if(c == 'z') return new Z; else PyErr_SetString(PyExc_ValueError, "Bad function argument"); } and export that function to Python. What is missing here is code that converts X*, Y* and Z* to PyObject*. How do I write that? Thank you, Johan

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[units] EE Acceleration, Velocity, Displacement in terms of decibels
by Michael Powell 04 Dec '11

04 Dec '11

Boost Units, Has anyone done any work, conversions, etc, with Acceleration, Velocity, Displacement (Length) in terms of decibels? dB, dBA, dBV, etc, and conversions to/from more "conventional" units like meters, meters per second, meters per second per second? I am learning, for example, that it is possibly to integrate across the Time dimension in order to yield Velocity from Acceleration, or similarly, Displacement (Length) from Velocity. I am doing a job with these type conversions going on across a spectrum analysis and would be interested in hooking up the calculations using boost::units to help enforce dimensional / unit integrity. Thanks... Best regards, Michael

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BOOST_THROW_EXCEPTION causing Abort Trap
by Kieran Simpson 04 Dec '11

04 Dec '11

I'm trying to use `boost::exception` and have condensed my prototype code down to the example in the Boost exception tutorial (http://www.boost.org/doc/libs/1_47_0/libs/exception/doc/tutorial_transporti…) however when running the code with the `BOOST_THROW_EXCEPTION` macro I get an abort from the program. #include <iostream> #include <boost/exception/all.hpp> typedef boost::error_info<struct tag_my_info,int> my_info; struct my_error: virtual boost::exception, virtual std::exception { }; void f() { BOOST_THROW_EXCEPTION(my_error() << my_info(42)); // Uncomment the below (and comment the above) for the program to work //throw my_error() << my_info(42); } int main(int argc, char** argv) { try { f(); } catch(my_error& x) { if(int const* mi = boost::get_error_info<my_info>(x)) { std::cout << "My info: " << *mi << std::endl; } } return 0; } Running the code with the BOOST_THROW_EXCEPTION macro: $ ./a.out Abort trap If as the comment says, I swap the code, all is well $ ./a.out My info: 42 Below is the output from the g++ preprocessor for f() void f() { ::boost::exception_detail::throw_exception_(my_error() << my_info(42),__PRETTY_FUNCTION__,"main.cpp",14); } Software versions are: $ g++ -v Using built-in specs. Target: x86_64-apple-darwin10 Thread model: posix gcc version 4.4.6 (GCC) $ port list boost boost @1.47.0 devel/boost I'm on OSX SL using the tools provided by MacPorts. I've double checked the g++ search paths and there's only one copy of the boost hpp files and that's the ones that belong to the aforementioned boost package. I have no idea why the abort trap is being called. I admit I'm newish to C++. I've also asked this question on StackOverflow (http://stackoverflow.com/questions/8256874/boost-throw-exception-causing-ab…) Cheers,

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Embedded python using boost
by Shane Kruk 03 Dec '11

03 Dec '11

I'm in the process of learning python, and embedding python into C++. I know very little about python so I've been playing around with many different types of interfaces and API's, with varying degrees of successes and failures. What I'm currently working on is the boost interface with C++. I am, however, stuck, for lack of a better word. Since the system I'm playing on is at work and on an isolated network, I do not have the ability to post the code directly to this forum. As such, I was able to print a copy of some experimental code, brought it home, and scanned it into a PDF file. I've attached the file(s) containing the code. If someone could please take a look at it and provide some advice as to what my problems are, it would be greatly appreciated. You'll notice some lines commented out as I've been experimenting with different things in an attempt to get something to work. My main problem at the moment is that the functions import(), eval(), and exec() cannot be found by the compiler. I get compiler errors indicating they are not declared in scope. I'm running on a redhat linux system (5.4) with a 1.33.1 version of boost. Python is version 2.4. I forgot to check the GNU C++ compiler version, but I'm guessing that probably doesn't matter.

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boost::posix_time::time_period - how to round seconds?
by qplace 03 Dec '11

03 Dec '11

I am building intervals using 0.5h increments (1800sec) in a cycle. The interval length is 1800sec also 8:30 am is used as start date. last of my interval looks like this: [2009-Apr-07 14:30:00/2009-Apr-07 14:59:59.999999] because of this weired endpoint my data with the timestamp of Apr-07 15:00:0000 does not fit into the interval How can I fix the interval to be [2009-Apr-07 14:30:00/2009-Apr-07 15:00:000000] ? Thanks

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[thread] Reducing the number of open tickets.
by Vicente J. Botet Escriba 03 Dec '11

03 Dec '11

Hi, I have committed the following tickets in trunk. Fixed Bugs: * [@http://svn.boost.org/trac/boost/ticket/2639 #2639] documentation should be extended(defer_lock, try_to_lock, ...). * [@http://svn.boost.org/trac/boost/ticket/3762 #3762] Thread can't be compiled with winscw (Codewarrior by Nokia). * [@http://svn.boost.org/trac/boost/ticket/3885 #3885] document about mix usage of boost.thread and native thread api. * [@http://svn.boost.org/trac/boost/ticket/3975 #3975] Incorrect precondition for promise::set_wait_callback(). * [@http://svn.boost.org/trac/boost/ticket/4480 #4480] OpenVMS patches for compiler issues workarounds. * [@http://svn.boost.org/trac/boost/ticket/4819 #4819] boost.thread's documentation misprints. * [@http://svn.boost.org/trac/boost/ticket/5423 #5423] thread issues with C++0x. * [@http://svn.boost.org/trac/boost/ticket/5739 #5739] set-but-not-used warnings with gcc-4.6 * [@http://svn.boost.org/trac/boost/ticket/6168 #6168] recursive_mutex is using wrong config symbol (possible typo). * [@http://svn.boost.org/trac/boost/ticket/6200 #6200] patch to have condition_variable and mutex error better handle EINTR. These are tickets with a simple solution or that had associated a complete patch or a clear solution. Anthony I would prefer that you do the merge so that you can check what goes on the release version. I have not closed the tickets. These tickets have just release 1.49 as Milestone. Please, close them when you merge to release. There were 113 tickets two days ago. There are now 114 tickets associated to Boost.Thread. I have closed some duplicates, but some news tickets have been created since. I would like to reduce by 10% the number of tickets every month. I encourage the Boost users that have created tickets for Boost to provide a clear an complete patch when possible so that we can reduce together the number of tickets associated to this Boost library and make it more portable/usable. Don't forget to provide tests that make evident the bug, or to add doc when you are proposing a anew feature. There are a lot of tickets associated to move semantics emulation. I have created a ticket to adapt Boost.Thread to Boost.Move hoping most of these bugs will be solved. As posted in another thread there is already a patch using Boost.Move that could be a good starting point. Of course the help offered by Ion will be too much appreciated. I have created another to adapt the interface to Boost.Chrono, but I will prefer to take care of this once the one for Boost.Move adaptation is committed, as the chance of collisions is big. On the mean time I will continue with some tickets specific to Windows platform. Best, Vicente

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[GIL] Saving DPI in PNG files
by PB 02 Dec '11

02 Dec '11

Hello, Is it possible to state a DPI setting when saving a PNG file using Boost' Generic Image Library? Thanks, Pete

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[serialization] Warning "type qualifier is meaningless on cast type" in extended_type_info_typeid.hpp
by Patrik Jonsson 02 Dec '11

02 Dec '11

Hi, When I compile code that uses the 1.48.0 serialization library with icpc 12.3.174, I get this warning, along with screenfuls of instantiation context: /n/home00/pjonsson/include/boost/serialization/extended_type_info_typeid.hpp(134): warning #191: type qualifier is meaningless on cast type static_cast<T const * const>(p) ^ This is the offending code: virtual void destroy(void const * const p) const { boost::serialization::access::destroy( static_cast<T const * const>(p) ); The compiler is complaining (correctly, I think) that you can't dictate whether something returned by value (here, the T const *) is const or not. Changing the cast to: static_cast<T const *>(p) makes the warning go away. Perhaps someone can make this change? Regards, /Patrik J.

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C0x11 threading capabilities
by Erotavlas_turbo＠libero.it 02 Dec '11

02 Dec '11

Hi, I have some question about the threading programming capabilities of boost library. First question: The new C++ standard C++11 has a support for threading programming. I have read some times ago, that with high probability the threading library of the C++11 should be the same of boost library? If it is true, can I use the boost thread library and in the future, when the C++ standard will be completed, could I transparently switching to it? What are the differencies between the boost thread library and the future C++11 thread library? Second question: this question is strictly related to the first one. At the moment GCC supports only a small subset of threading programming features http: //wiki.apache.org/stdcxx/C++0xCompilerSupport. So using thread boost library allows me to use the full features of future C++ standard library? Or I'm limited by the compiler? Last question: what about the OpenMP directives? How they are different in terms power and flexibility for the parallel programming task respect to the boost library? Thank you Best Regards

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Changelog for 1.47.0 does not properly warn about critical bug
by Paul Harris 02 Dec '11

02 Dec '11

Hello, I discovered this bug by accident https://svn.boost.org/trac/boost/changeset/68866 which was only linked via the ticket mentioned below, The code below demonstrates that ANY wide-character string of the same length resolves to the same UUID ! Thats pretty darn serious, I expected to see a much more serious mention in the Changelog in boost 1.47.0... for UUID, there was only a mention of a few tickets including this one: https://svn.boost.org/trac/boost/ticket/5145 which only mentioned a WARNING in the description ! "Fixed warning: use of logical && with constant operand; switch to bitwise & or remove constant [-Wconstant-logical-operand]" Surely it should say something like "UUIDs for wide character strings are totally wrong" Note also that the Changelog link for UUID goes to Utility, not UUID. The code: #include <boost/uuid/name_generator.hpp> #include <boost/uuid/nil_generator.hpp> #include <boost/uuid/uuid_io.hpp> #include <iostream> using namespace boost::uuids; using namespace std; int main() { { cout << "WIDE" << endl; const wchar_t* a = L"one long string that is something like this and that blahh"; const wchar_t* b = L"hello there you long long string that looks nothing like t"; nil_generator nil; name_generator na(nil()); name_generator nb(nil()); uuid ua = na(a); uuid ub = nb(b); cout << to_string(ua) << endl; cout << to_string(ub) << endl; } { cout << "NARROW" << endl; const char* a = "one long string that is something like this and that blahh"; const char* b = "hello there you long long string that looks nothing like t"; nil_generator nil; name_generator na(nil()); name_generator nb(nil()); uuid ua = na(a); uuid ub = nb(b); cout << to_string(ua) << endl; cout << to_string(ub) << endl; } return 0; } the result: $ g++ main.cpp && ./a.out WIDE 4ffa48af-9685-5089-97ac-fe6627ead94c 4ffa48af-9685-5089-97ac-fe6627ead94c NARROW 73030b72-a864-5c7b-9963-c0bedff1283e da8943a6-26c9-5641-bd37-427b1b70d619 $ The two different wchar_t strings resolve to the same uuid !!! What am I doing wrong? thanks Paul

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