August 2005 - Boost-users - lists.preview.boost.org

Re: [Boost-users] [BULK] Re: [range] From 1.33.0 gives new warning vs 1.32
by Sohail Somani 18 Aug '05

18 Aug '05

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Thorsten Ottosen > Sent: Monday, August 15, 2005 11:17 AM > To: boost-users(a)lists.boost.org > Subject: [BULK] Re: [Boost-users] [range] From 1.33.0 gives > new warning vs 1.32 > Importance: Low > > > > "Kevin Wheatley" <hxpro(a)cinesite.co.uk> wrote in message > news:4300715B.ED49E94C@cinesite.co.uk... > > I had some code that with 1.32 compiled fine when compiled with > > warnings as errors, but now with 1.33 I get: > > > Compiled with gcc 3.2.3 under Linux, > > > > perhaps something like this is needed? > > > template< class Char > > > inline Char* str_end( Char* s ) > > { > > - return (Char*)str_end( s, s ); > > + return const_cast<Char*>(str_end( s, s )); > > what's the difference? A c-style cast is also a const-cast. You didn't just say that.

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I find a error in the document of boost 1.33
by 沈慧峰 18 Aug '05

18 Aug '05

The example of "boost/doc/html/date_time/examples.html#date_time.examples.month_add" can not be compiled. I use the vc71+stlport 4.62, the command line is cl /MD /EHsc /DBOOST_LIB_DIAGNOSTIC. I also can not find this example code under the directory "boost\libs\date_time\example\gregorian\". The example code is : /* Simple program that uses the gregorian calendar to progress by exactly * one month, irregardless of how many days are in that month. * * This method can be used as an alternative to iterators */ #include "boost/date_time/gregorian/gregorian.hpp" #include <iostream> int main() { using namespace boost::gregorian; date d = day_clock::local_day(); add_month mf(1); date d2 = d + mf.get_offset(d); std::cout << "Today is: " << to_simple_string(d) << ".\n" << "One month from today will be: " << to_simple_string(d2) << std::endl; return 0; }

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thread safety of the mutex ctor
by James E Taylor 18 Aug '05

18 Aug '05

I hope this isn't a stupid question, but.... Is the boost mutex constructor thread-safe? I am writing a singleton template and trying to avoid the static initialisation/destruction order fiasco. I envisage two threads accessing a function like this concurrently: template<typename T> boost::shared_ptr<T> my_func() { static boost::mutex m; boost::mutex::scoped_lock l(m); static boost::shared_ptr<T> p(new T); return p; } and my worry is that both threads could attempt to do the static initialisation of m concurrently. Is there protection against this? Is it even possible to protect against this? I've tried to use boost::call_once, which would give sufficient guarantees but it's quite inflexible as nothing can be passed to or from the function being called. I know that integral types (like a pthread_t) of static storage are initialised before main() and before constructors of statically allocated objects are called, which means there would be no problem using a pthread_t above. However, constructors of objects of static storage are called at a time when there could be multiple threads running. Am I worrying about nothing? Or is there a problem here? Thanks, James -- James E Taylor ___________________________________ NOCC, http://nocc.sourceforge.net

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Re: [Boost-users] Boost-users Digest, Vol 637, Issue 1
by James E Taylor 18 Aug '05

18 Aug '05

Thanks, Pablo, I'll have a look at it. James > FYI Matthew Wilson gave a technique (in "Imperfect C++&quot for handling > this, > by turning the mutex initialization into an integer initialization (that > doesn't have a problem with [multiple] simultaneous threads entering the > function) > > It uses STLSoft's spin_mutex, and looks pretty much like what you have > already: > > <code> > #include <platformstl/spin_mutex.hpp> > #include <stlsoft/lock_scope.hpp> > using platformstl::spin_mutex; > using stlsoft::lock_scope; > > template<typename T> > boost::shared_ptr<T> > my_func() > { > // static boost::mutex m; > // boost::mutex::scoped_lock l(m); > static int spin_count = 0; // No race condition initializing an > int > spin_mutex mutex(&spin_count); // Build the mutex on top of the > static > int > lock_scope lock(mutex); > > static boost::shared_ptr<T> p(new T); > return p; > } > </code> > > This assumes, of course, you can (and are willing to) use STLSoft... > > > HTH, > Pablo ___________________________________ NOCC, http://nocc.sourceforge.net

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Random access to sequences
by Stephen Gross 18 Aug '05

18 Aug '05

I read up on boost::mpl::at<...>. It's pretty cool, but I wanted to make it a little easier to use. I found it a little annoying to have to type out 'int_<...>' for the index number, so I created a struct to automate that feature: ========================== template<typename SEQ, int IDX> struct atIdx { typedef typename boost::mpl::at<SEQ, boost::mpl::int_<IDX> >::type type; }; ========================== With the struct above, you can do the following: ============================= typedef boost::mpl::vector<int, char, int> t; atIdx<t, 0>::type i; // This line is shorter than the one below: /* atIdx<t, boost::mpl::int_<0> >::type i; */ ============================= Is this feature already available in boost somewhere? If I've reinvented the wheel, I'll be happy to use an existing implementation... Thanks, --Steve Stephen Gross Case Western School of Medicine Cleveland, OH "By Grabthar's hammer, by the sons of Worvan, you shall be avenged." - Dr. Lazarus

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Re: [Boost-users] thread safety of the mutex ctor
by Christopher Hunt 17 Aug '05

17 Aug '05

On 18/08/2005, at 1:19 AM, boost-users-request(a)lists.boost.org wrote: > I envisage two threads accessing a function like this concurrently: > > template<typename T> > boost::shared_ptr<T> > my_func() > { > static boost::mutex m; > boost::mutex::scoped_lock l(m); > > static boost::shared_ptr<T> p(new T); > return p; > } > > and my worry is that both threads could attempt to do the static > initialisation of m concurrently. Is there protection against this? > Is it even possible to protect against this? The scope of m is actually outside of your function given that it is static. Thus it will be initialised outside of your function generally before any other threads get to start up. Cheers, -C

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Wave capabilities
by Foster Gareth 17 Aug '05

17 Aug '05

Hello list, I've been reading through the wave docs, it looks very impressive. I was wondering, is it possible to use Wave to extract all the macro/class/function definitions with their respective line numbers from a source file? I noticed the mention of include paths etc however, does this mean that just throwing random source files from a large source tree at Wave, with no regard for whether or not all the types in it will be defined, is going to result in it throwing exceptions? Thanks for any help. Cheers, Gaz ********************************************** * http://www.mozilla.org/products/firefox/ * **********************************************

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[Signals] Boost.signals dll version crashes on OS X
by Chiedo Acholonu 17 Aug '05

17 Aug '05

I built the boost.signals library using bjam and am trying to use it in an xcode project named TestSignals. The project only consists of the signals library and the maximum.cpp example file (boost-root/libs/signals/example/maximum.cpp). The project builds but it crashes with a SIGBUS signal 10 when run. This only happens with the dynamic version of signals. I have defined BOOST_SIGNALS_DYN_LINK and built the library multithreaded, so I'm not sure what I'm doing wrong. I'm running OS X 10.4.2 with Xcode 2.1. Here is a snippet of the crash log (I can post the rest on request): Exception: EXC_BAD_ACCESS (0x0001) Codes: KERN_PROTECTION_FAILURE (0x0002) at 0x00000000 Thread 0 Crashed: 0 maximum.ob 0x0040c824 std::less<int>::operator()(int const&, int const&) const + 48 (stl_function.h:227) 1 maximum.ob 0x0040e0d8 boost::signals::detail::any_bridge_compare<std::less<int>, int>::operator()(boost::any const&, boost::any const&) const + 364 (named_slot_map.hpp:62) 2 maximum.ob 0x0040e148 boost::detail::function::function_obj_invoker2<boost::signals::detail::any_bridge_compare<std::less<int>, int>, bool, boost::any, boost::any>::invoke(boost::detail::function::any_pointer, boost::any, boost::any) + 76 (function_template.hpp:119) Any help would be much appreciated. Chiedo

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boost:signals SIGSEV
by Massimiliano Liccardo 17 Aug '05

17 Aug '05

I opened the bug https://sourceforge.net/tracker/index.php?func=detail&aid=1262038&group_id=… concerning a segmentation fault using the boost:signals library. I attached the source i used. bye -- Massimiliano Liccardo (maX) <liccardo(a)acmesolutions.it> jid:coccolesto@jabber.org GnuPG public key available on wwwkeys.eu.pgp.net Key ID: D01F1CAD Key fingerprint: 992D 91B7 9682 9735 12C9 402D AD3F E4BB D01F 1CAD "la velocità induce all'oblio, la lentezza al ricordo"

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[Regex] regex_match changed to match_any in 1.33?
by John Sichi 17 Aug '05

17 Aug '05

In boost/regex/v4/regex_match.hpp, a number of the overloads (the ones that don't take a result parameter) are now bitwise-oring in regex_constants::match_any. As a result, a sequence like boost::regexp exp("a(bc)?") char *value = "abcbc"; bool result = boost::regex_match(value, value + 5, exp); will now set result to true where it was previously false in 1.32. I fixed our code by passing in a dummy result object as an extra parameter. Was this change intentional? I couldn't find any documentation that mentions it. JVS

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