March 2009 - Boost-users - lists.boost.org

[BGL] citing the Boost Graph Library
by Alejandro Marcos Aragón 06 May '09

06 May '09

Can anyone point me how to cite the Boost Graph Library in a paper? Is there any information in the boost website? Thank you all, Alejandro Aragón

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[concept check][mpl] (Conditional) Concept checking for functions
by Jesse Perla 21 Apr '09

21 Apr '09

I have a variety of user defined function objects that I will need to call. Take the following examples:template<int N1, int N2 = 0> struct Func1{ double operator()(boost::array<double, N1>& x1, boost::array<double, N2>& x2){...}}; template<int N1> struct Func2{ double operator()(boost::array<double, N1>& x){...}}; With a function such as template<int N1, int N2 = 0, class F = boost::function<double (boost::array<double, N1>& x1, boost::array<double, N2>& x2)> class DPP{ void solve(){...... uses F...to be discussed} }; I have a few questions: 1) Is there a relatively easy way to use boost concept check to verify that F follows the first function signature so that I can detect compile time the problem? I can't figure out how to do it from the concept check docs, and they say they are out of date. Usage I want to check in the instantiation of DPP: F f; f(boost::array<double, N1>& x1, boost::array<double, N2>& x2) 2) I want the user to be able to pass in a simplified function type if N2 = 0 I assume that to call the actual function I would have some kind of impl function with partial specialization such as: template<bool use_simplified, int N1, int N2> struct use_f_impl(); template<int N1, int N2> struct use_f_impl<true, N1, N2>{ static double use_f() { STATIC_ASSERT(N2 == 0); F f; boost::array<double, N1> x; return f(x); } }; template<int N1, int N2> struct use_f_impl<false, N1, N2>{ static double use_f() { F f; boost::array<double, N1> x1; boost::array<double, N2> x2; return f(x1, x2); } }; And then in my solve() function I go: double val = use_f<(N2 == 0, N1, N2)>::use_f(); Is this the right idiom, pattern, etc? Do I need to use the struct with a static function since function templates don't have partial specialization? 3) Now what if I want to do a concept check on the F passed into DPP? It has to be conditional on the N2 value now. How would I do this? 4) Lets say that I don't want to force them to use the simplified version of the function signature if they don't want to. Can I automatically detect the signature and put it into a flag integer in the class? i.e. inside of the DPP class: static bool use_simple = IsSimple<F>::value; Then pass in the use_simple value when calling use_f_impl. If so, what would the IsSimple metafunction look like and can concept check help? Thanks, Jesse

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[coroutine] Bus error on Mac OS X 10.5
by Nat Goodspeed 16 Apr '09

16 Apr '09

I've downloaded the not-yet-Boost coroutine library [1] from the Boost Vault [2]. On a couple of Linux platforms I was able to build and run example/banana.cpp -- though I had to patch noreturn.hpp for gcc 3.3 [3]. On an Intel "fall 2008" MacBook Pro running OS X 10.5.6, with Apple gcc 4.0.1, I had to comment out the MAP_ANONYMOUS mmap() flag [4] -- I don't think that flag is available in Darwin. (Obviously that patch should test for MAP_ANONYMOUS rather than simply suppressing it.) Having done that, the 'banana' example program built -- but I get a bus error trying to run it. I did find an exchange on the Apple mailing list [5] in which Kevin Van Vechten recommends #defining _XOPEN_SOURCE before #include <ucontext.h>: >> Why the bus error? What am I doing wrong? > This is a known issue where getcontext(3) is writing past the end of > the ucontext_t struct when _XOPEN_SOURCE is not defined > (rdar://problem/5578699 ). As a workaround, define _XOPEN_SOURCE > before including ucontext.h. Unfortunately, adding such a #define [6] does not resolve my bus error. The article [7] in which I found ref [5] proposes a classic-C program [8] to illustrate use of getcontext() and swapcontext(). On my Mac, that program produces a seg fault with or without #define _XOPEN_SOURCE. So my apologies: this may very well not be a Boost issue, or even a pre-Boost issue. I'm very excited to try the coroutine library, but crashing on Macs is a show-stopper for us. Has anyone else succeeded in running it on a Mac? [1] http://www.crystalclearsoftware.com/soc/coroutine/index.html [2] http://www.boostpro.com/vault/index.php?action=downloadfile&filename=boost-… [3] attached boost-coroutine.gcc33.patch [4] attached boost-coroutine.osx-mmap.patch [5] http://lists.apple.com/archives/darwin-dev/2008/Jan/msg00232.html [6] attached boost-coroutine.osx-context.patch [7] http://hjiang.net/archives/220 [8] attached swapcontext_test.c *** boost/coroutine/detail/noreturn.hpp~ Sun Aug 20 10:11:09 2006 --- boost/coroutine/detail/noreturn.hpp Fri Mar 27 17:00:00 2009 *************** *** 40,48 **** --- 40,54 ---- #if defined(__GNUC__) + #if __GNUC_MAJOR__ > 3 || (__GNUC_MAJOR__ == 3 && __GNUC_MINOR__ > 3) #define BOOST_COROUTINE_NORETURN(function) \ function __attribute__((__noreturn__)) \ /**/ + #else // gcc 3.3 + #define BOOST_COROUTINE_NORETURN(function) \ + function + /**/ + #endif // gcc 3.3 #elif defined (BOOST_MSVC) *** boost/coroutine/detail/posix_utility.hpp~ Sun Aug 20 13:11:09 2006 --- boost/coroutine/detail/posix_utility.hpp Fri Mar 27 18:52:17 2009 *************** *** 129,135 **** void * stack = ::mmap(NULL, size, PROT_EXEC|PROT_READ|PROT_WRITE, ! MAP_PRIVATE|MAP_ANONYMOUS, -1, 0 ); --- 129,135 ---- void * stack = ::mmap(NULL, size, PROT_EXEC|PROT_READ|PROT_WRITE, ! MAP_PRIVATE /*|MAP_ANONYMOUS*/, -1, 0 ); *** boost/coroutine/detail/context_posix.hpp~ Sun Aug 20 13:11:09 2006 --- boost/coroutine/detail/context_posix.hpp Fri Mar 27 20:57:44 2009 *************** *** 42,47 **** --- 42,56 ---- * NOTE2: makecontext and friends are declared obsolescent in SuSv3, but * it is unlikely that they will be removed any time soon. */ + // NOTE3 (per http://lists.apple.com/archives/darwin-dev/2008/Jan/msg00232.html) + // > Why the bus error? What am I doing wrong? + // This is a known issue where getcontext(3) is writing past the end of the + // ucontext_t struct when _XOPEN_SOURCE is not defined (rdar://problem/5578699 ). + // As a workaround, define _XOPEN_SOURCE before including ucontext.h. + // [While we could make that OSX-specific, it seems harmless enough?] + #ifndef _XOPEN_SOURCE + #define _XOPEN_SOURCE + #endif #include <ucontext.h> #include <boost/noncopyable.hpp> #include <boost/coroutine/exception.hpp> // From http://hjiang.net/archives/220 #include <signal.h> #include <stdio.h> // NOTE (per http://lists.apple.com/archives/darwin-dev/2008/Jan/msg00232.html) // > Why the bus error? What am I doing wrong? // This is a known issue where getcontext(3) is writing past the end of the // ucontext_t struct when _XOPEN_SOURCE is not defined (rdar://problem/5578699 ). // As a workaround, define _XOPEN_SOURCE before including ucontext.h. // [While we could make that OSX-specific, it seems harmless enough?] #ifndef _XOPEN_SOURCE //#define _XOPEN_SOURCE #endif #include <ucontext.h> // Signals which routine should run. volatile int g_turn; void routineOne(ucontext_t* self, ucontext_t* other) { int numbers[] = {1, 2, 3}; int i; for (i = 0; i < sizeof(numbers)/sizeof(int); ++i) { printf("Routine one: %d\n", numbers[i]); // Call other with current continuation if (g_turn != 1) { g_turn = 1; swapcontext(self, other); } } } void routineTwo(ucontext_t* self, ucontext_t* other) { int numbers[] = {-1, -2, -3}; int i; for (i = 0; i < sizeof(numbers)/sizeof(int); ++i) { printf("Routine two: %d\n", numbers[i]); if (g_turn != 2) { g_turn = 2; swapcontext(self, other); } } } int main() { // Continuations ucontext_t cont_one; ucontext_t cont_two; ucontext_t cont_main; // one stack for each thread char stack_one[SIGSTKSZ]; char stack_two[SIGSTKSZ]; // Initialize the coutinuations. cont_one.uc_link = &cont_main; cont_one.uc_stack.ss_sp = stack_one; cont_one.uc_stack.ss_size = sizeof(stack_one); cont_two.uc_link = &cont_main; cont_two.uc_stack.ss_sp = stack_two; cont_two.uc_stack.ss_size = sizeof(stack_two); getcontext(&cont_one); makecontext(&cont_one, (void (*)())routineOne, 2, &cont_one, &cont_two); getcontext(&cont_two); makecontext(&cont_two, (void (*)())routineTwo, 2, &cont_two, &cont_one); g_turn = 0; // Call routineOne with current continuation. Continue from here // after routineOne finishes. getcontext(&cont_main); if (g_turn == 0) { setcontext(&cont_one); } return 0; }

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[serialization] appending elements
by Agustín K-ballo Bergé 08 Apr '09

08 Apr '09

Is it possible to append serialized elements to an existing archive? I need to keep a set of records on a file, and periodically add new entries to it (kind of like a database table). Reading the whole set, adding the new records, and serializing the set back is not an option since I expect the set to go pretty big. I have tried to keep several archives at the same stream (with no_header and no_tracking flags), but then I don't know how to read them. Reading them as if they were a single archive does not work, should it? Agustín K-ballo Bergé.-

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[ASIO] Windows native type for ASIO serial port?
by Jeff Diewald 03 Apr '09

03 Apr '09

I have a boost::asio::serial_port object. What is the specific Windows type returned by native()? I'm having trouble with my serial communication across the serial port, and want to get more diagnostic information by going to the native level. The serial port hangs occasionally on a synchronous read_some call, and I haven't been able to figure out why. Ideally, I'd like to build a timeout into the synchronous call. Any help is appreciated, Jeff Diewald JEOL USA

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[Q] eliminating false memory leak reports
by V S P 03 Apr '09

03 Apr '09

Hello, I have a class (below), and MS memory leak detector reports a leak on ptr.reset I have redefined 'new' as follows: #define MYDEBUG_NEW new( _NORMAL_BLOCK, __FILE__, __LINE__) In another example, also below I have an _impl structure that is allocated and assign to typedef boost::shared_ptr<cmoney_impl_dtl> t_money_storage; My understanding is that it is a 'false' detection is that correct? In otherwords, in my thinking -- as long as I have assigned an object to boost::shared_ptr -- I do not have remember anything about it anymore. (using visual studio 2008, 32 bit) Another question, since I have all of my heap objects using boost::shared_ptr is there any free tool that I can use to verify that those things do not leak (as some of the are actually DB connections so it is important for them to get completely destroyed). Thank you in advance ---------------------------- template <typename TThrdData> struct CService_ThreadData:private boost::noncopyable { CService_ThreadData (void){}; ~CService_ThreadData (void){}; ///creates a new thread data object if does not exists //Call this from every thread to establish thread's data //manager object static TThrdData& getdata(void) { /* YES, using static variable in this case is safe, because it is in the 'global' scope and therefore is intialized before Main starts Otherwise, static variables are not thread safe */ if (ptr.get() == 0) { ptr.reset(new TThrdData()); } return (TThrdData&)(*ptr); } private: static boost::thread_specific_ptr<TThrdData> ptr; };//end of class -------------------------- cmoney_t::cmoney_t (void) :v(new cmoney_impl_dtl) { } -- V S P toreason(a)fastmail.fm -- http://www.fastmail.fm - Access your email from home and the web

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new idea for project
by divyanshu singh 02 Apr '09

02 Apr '09

HI all I am new to boost and i found its math function library really cool I like to play with numbers specially prime numbers I am thinking of developing a new library for boost that can generate various prime patterns adn will include other new algorithms related to prime numbers like aks algorithm to test whether a number is prime,Prime spiral algorithm,prime number generation algorithm This library can help people who love numbers and want to find new prime or number patterns first i would like to know that whether such library already exists in boost if not then hows the idea?

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move() aware containers?
by Noah Roberts 01 Apr '09

01 Apr '09

I'm reading a pre-release of a book on C++0x threading. I'm using the boost::thread library since it's supposed to be pretty close. Now they're using std::vector<> though and I know it's not move ready. Is there a boost container I can mimic this with?

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boost exception tutorial
by Robert Ramey 01 Apr '09

01 Apr '09

I'm investigating boost exception to see if it is helpful in a particular instance. I start by looking at the first Tutorial. I can't see how this is better than struc my_error : public std::exception { int m_ errno; my_error(int errno) : m_errno(errno) {} }; ... throw my_error(errno) try { ... } catch(my_error e){ cerr << e; } What am I missing here? This first example is two compilicated in that it requires that I delve into a bunch of other stuff (operator << for exception data?) and it doesn't provide any motivation. I think it would be more useful if it "spoon fed" the reader (me in this case) a little more. Something like: Traditional simple example like that above. explanation of why the example isn't "good enough" simple example reformulated using boost exception explanation of how this addresses the short comings of the original version. I think this would motivate more users to transition to the library. Robert Ramey

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mpl::for_each state
by Skelly, Luke 01 Apr '09

01 Apr '09

Please ignore my last message. I somehow accidentally sent it while still editing! I am trying to create a std::map from an mpl::map. I've been trying to figure out how to use mpl::for_each to accomplish this. The problem I have is that the runtime function is passed to for_each by value and returns void. All the examples I've seen for mpl::for_each involve printing and not creating any new objects. Here is the attempt I've made: // creates std::map<size_t,size_t> from mpl::map<size_t,size_t> template<typename TypeMap> struct MapMaker { typedef std::map<size_t, size_t> map_type; map_type func_map; MapMaker() { boost::mpl::for_each<TypeMap>(*this); } template<typename U> void operator()(U x) { func_map[U::first::value]=U::second::value; } func_type operator[](size_t i) { return func_map[i]; } }; typedef boost::mpl::map< boost::mpl::pair<boost::mpl::size_t<1>, boost::mpl::size_t<2> >, boost::mpl::pair<boost::mpl::size_t<2>, boost::mpl::size_t<24> >, > myMap; int main() { MapMaker<myMap> m; size_t result = m[1]; } Of course this is a simplified version of what I'm really trying to do, which is create a map to function pointers. The problem is in the call to mpl::for_each in the MapMaker constructor. The std::map is created, but never returned. I've considered making func_map static, but that complicates things quite a bit, especially since MapMaker it is a class template. Luke Skelly

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