- Boost - lists.boost.org

[unnullable_ptr] Proposal for a new library
by Angel Tsankov 02 Aug '08

02 Aug '08

Hello, Is there any interest in a class template which acts like a pointer and guarantees at compile time and at no CPU or memory cost (except when a call to any of its methods is not inlined) that the pointer is not null? One of the applications that I have found for this template is in defensive programming to eliminate the chances that dereferencing a pointer will result in undefined behaviour (when the pointer is null). Using this template is superior to any alternative method (that I know) to achieve the same result, since: (*) it consumes no CPU (in contrast to null checks); (*) the class template instances are copy constructible and copy assignable (in contrast to references which can also be used to guarantee unnullability); (*) it is natively supported by the language and provides a 'real' guarantee (in contrast to 'design by contract'); (*) supports the natural syntax for access to the wrapped resource (in constrast to boost::ref). Regards, Angel Tsankov

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[shifted_ptr] STL support works at 90% (...!)
by Phil Bouchard 02 Aug '08

02 Aug '08

I've finalized the ad extremum idea of STL support of smart pointers such as shifted_ptr which is a good example to use because of the distinct types it is using as pointer types (T *, shifted<T> *, shifted_allocator::pointer, etc.). I have 2 patch files that can be used as an example to add support for real smart pointers using Gcc's STL. These are located in the bits/ folder. These are Gnu related but I wanted to share this here for objectivity. I have added special contructors in shifted_ptr that takes raw pointers (T *) instead of the type safe shifted<T> *. This is temporary until I add the proper casts inside the STL code. What else? I simplified shifted_allocator and fixed abominable bugs in shifted_ptr created by these temporary constructors added. Now I'm pretty dang happy about it... There are still some I need to fix and some more are yet to be found but it should be much easier now. Once again I am using shifted_ptr_test2.cpp as my main test application. Later, -Phil

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Possible library submissions: fuzzy logic library, new container
by Alex Shafir 01 Aug '08

01 Aug '08

I am trying to determine if there might be any interest in a couple of possible library submissions. Both ideas were very useful and instrumental for many C++ development projects that I was doing for the last years. The fuzzy logic library is a simple, pure C++, optimized for speed, practical implementation of the fuzzy logic calculations that DOES NOT attempts to comply with the FCL(Fuzzy Control Language) standard (like IEC 1131). It CANNOT load FCL files. Instead similar to the Boost Spirit framework it provides a syntax that enables fuzzy logic rules to be written exclusively in C++. Compiled fuzzy model specifications are immediately executable. A snippet of what this syntax currently looks like is at the end of this message. The other idea is the “sparse array” container. Working for securities trading industry I used it innumerable number of times. It is useful in situations where there is a set of entities identified by integer(unsigned) numbers. Most often the numbers are identity keys in a database, a protocol field ids, etc. The potential range of the numbers makes it impractical to use a C++ array or the STL <vector>. On the other hand the average percentage of the keys that are really used in an application relative to the potential range is often less then 5% and there are huge holes of unused keys between zero and max(used key). The data elements or pointers to objects are kept in a structure similar to a balanced B-tree. Elements are directly accessed by an index operator. Access involves only a few arithmetic and redirection operations. When storing a new element that is outside of the range provided by exiting data structure the structure bilds itself up extending the indes range enough to accommodate a new index value. Existing data are never physically moved like in the STL vector. So, all references/pointers/iterators referencing existing elements are never invalidated. Feel free to comment. Fuzzy model syntax sample: ======================================== #include "TestModel.h" using namespace Fuzzy; // test model definition TestModel::TestModel(string file): Model(file), angle(-1), velocity(-1), speed(-1) { // fuzzy variables definitions created by the base class (Fuzzy::Model) // Input/Output methods; Input/Output arguments are refs // to double scalar variables Var& Angle = Input(angle); Var& Vlcty = Input(velocity); Var& Speed = Output(speed); // membership functions definitions created by fuzzy variables // Term method; Term method takes curve name as an argument; // cureve names are defined in the Fuzzy::Model curve definition // file MemFun& AngleNegHigh = Angle.Term("AngleNegHigh"); MemFun& AngleNegLow = Angle.Term("AngleNegLow"); MemFun& AngleZero = Angle.Term("AngleZero"); MemFun& AnglePosLow = Angle.Term("AnglePosLow"); MemFun& AnglePosHigh = Angle.Term("AnglePosHigh"); MemFun& VlctyNegHigh = Vlcty.Term("VelocityNegHigh"); MemFun& VlctyNegLow = Vlcty.Term("VelocityNegLow"); MemFun& VlctyZero = Vlcty.Term("VelocityZero"); MemFun& VlctyPosLow = Vlcty.Term("VelocityPosLow"); MemFun& VlctyPosHigh = Vlcty.Term("VelocityPosHigh"); MemFun& SpeedNegHigh = Speed.Term("AngleNegHigh"); MemFun& SpeedNegLow = Speed.Term("AngleNegLow"); MemFun& SpeedZero = Speed.Term("AngleZero"); MemFun& SpeedPosLow = Speed.Term("AnglePosLow"); MemFun& SpeedPosHigh = Speed.Term("AnglePosHigh"); // these are the model rules; syntax is pretty strightforward; // rules look like operator >> where lhs is the condition and // rhs is the conclusion; // lhs and rhs have to be in parens if they contain more then // one term because of the c++ operators precedence rules; // conclusion may be a comma separated list of output terms // in parens ((AngleZero and VlctyZero)or(AnglePosLow and VlctyNegLow)or(AngleNegLow and VlctyPosLow)) >> SpeedZero; ((AngleZero and VlctyNegLow)or(AngleNegLow and VlctyZero)) >> SpeedNegLow; ((AnglePosLow and VlctyZero)or(AngleZero and VlctyPosLow)) >> SpeedPosLow; ((AngleZero and VlctyNegHigh)or(AngleNegHigh and VlctyZero)) >> SpeedNegHigh; ((AnglePosHigh and VlctyZero)or(AngleZero and VlctyPosHigh)) >> SpeedPosHigh; } TestModel::~TestModel() { } void TestModel::run(double a, double v, double &s) { // we assign scalar variables to class members angle = a; velocity = v; speed = s; // then run the model // it should be pretty fast as it all designed to preallocate // all the needed large objects in the model constructor Model::run(); // and assign the values of output variables s = speed; }

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dll-path feature
by brook＠biology.nmsu.edu 01 Aug '08

01 Aug '08

It seems that I need to use the dll-path feature to add an -rpath directive to the linker when my boost libraries are installed. This seems to be described (mostly) fairly clearly at http://www.boost.org/boost-build2/doc/html/bbv2/faq/dll-path.html What is not clear is where the feature should be invoked. My attempt to modify Jamroot to add <dll-path> to the boost-install rule failed in the sense that not rpath information makes it into the installed libraries. (The rest of this snippet is the original.). rule boost-install ( libraries * ) { package.install install : <dependency>/boost//install-headers $(install-requirements) : # No binaries : $(libraries) : # No headers, it's handled by the dependency ; install stage : $(libraries) : <location>$(BOOST_STAGE_LOCATE) <dll-path>/path/to/add/via/rpath ; local c = [ project.current ] ; local project-module = [ $(c).project-module ] ; module $(project-module) { explicit stage ; explicit install ; } } So, how is one supposed to invoke the <dll-path> feature in order to have -rpath added to the linking of libraries during their installation? Thanks for your help. Cheers, Brook

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[1.36.0 beta] Bug fix procedures
by Beman Dawes 01 Aug '08

01 Aug '08

Bug reports from the beta are starting to surface on the user's list. Here is the procedure for dealing with them: * Apply the fix to the trunk. * Wait until enough regression tests have cycled to demonstrate that the fix worked and didn't break anything else. * Apply the fix to branches/release. * Keep an eye on the release test results to be sure there were no unintended consequences. In other words, there is no need to ask the release managers for permission to apply to branches/release as long as tests are clean. The whole point of doing a beta is to shake these user detected bugs out of the woodwork and apply the resulting fixes in time for the release. Thanks, --Beman

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fixed-pt [improved]
by Neal Becker 01 Aug '08

01 Aug '08

Here is an improved version of fixed-pt, incorporating some of the suggestions given here:

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[release] xpressive bug fix
by Eric Niebler 01 Aug '08

01 Aug '08

What are the chances that I'll be able to merge a bug fix to the release branch? This one: http://svn.boost.org/trac/boost/ticket/2157 just came in, and I've already fixed it on trunk. Assuming that the next cycle of the trunk tests don't show anything amiss, would I be permitted to merge the fix? The bug will not cause crashes, but it will lead to incorrect results when matching the end-of-line assertion ($) against internal line breaks, which is fairly common usage scenario. I have high confidence in the fix. These are the relevant changesets: http://svn.boost.org/trac/boost/changeset/47899 http://svn.boost.org/trac/boost/changeset/47901 -- Eric Niebler BoostPro Computing http://www.boostpro.com

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1.36 documentation
by Daniel James 01 Aug '08

01 Aug '08

Hello everyone, Since the generated documentation isn't currently included in the snapshots, I've temporarily made it available here: http://www.calamity.org.uk/1.36/ Hopefully, the documentation should be integrated with the beta site soon after the beta release. Daniel

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[swap] End-user allowed to add overloads to boost namespace?
by Niels Dekker - mail address until 2008-12-31 31 Jul '08

31 Jul '08

Is any end-user allowed to add her own overloads of existing Boost functions to the boost namespace? The boost::swap utility from Joseph Gauterin (recently moved to the trunk) allows the user to customize boost::swap for her class, by providing a swap function for her class within the namespace of the class. Internally boost::swap does the idiomatical "using std::swap; swap(left,right);", to allow finding such a user-provided swap function by argument-dependent lookup (ADL) <svn.boost.org/svn/boost/trunk/boost/utility/swap.hpp> Unfortunately some compilers don't fully supported ADL, as is shown by the mixed test results of swap/test/specialized_in_global.cpp and swap/test/specialized_in_other.cpp, at http://www.boost.org/development/tests/trunk/developer/utility-swap_.html ADL failures appear to occur for GCC 3.3.1 (PathScale), Intel C++ 8.1, MSVC 7.1 (2003), and Borland (up to 5.9.3). Once the boost::swap utility would be used by other Boost libraries, end users might want to add a custom overload of swap for their classes to the boost namespace. Especially when users would have to deal with lacking ADL support of their compiler. Would it be okay for them to do so? Or are there some moral objections, or technical issues, regarding a user-provided overload within the boost namespace? Kind regards, Niels PS Volodya, thanks for fixing swap/Jamfile.v2! -- Niels Dekker http://www.xs4all.nl/~nd/dekkerware Scientific programmer at LKEB, Leiden University Medical Center

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boost versus Apple's gcc 4.2
by Mat Marcus 31 Jul '08

31 Jul '08

On the boost users list, there was a discussion about some issues arising with boost versus gcc-4.2 on Apple systems. One interesting issue arises from the fact that Apple decoupled the gcc compiler version from the lib version. They "own" libstdc++, which they've kept at version 4.0 even when the 4.2 compiler. This breaks some assumptions in boost headers. I am reposting on the main developer list: ### Peter Dimov wrote: > Is the new Apple GCC documented somewhere? I wasn't able to find anything > related to a new assembler syntax or -fasm-blocks. Can you ask Apple to > explain the issue? Stock g++ 4.2.x compiles the code, so the problem must be > Apple-specific. Ok, I've got a little bit more information on the Apple gcc 4.2 situation. Here is a snippet from an email dialog between a user and an apple compiler engineer: user appears below with with prefix ">>" apple compiler engineer appears below with with prefix ">" >> Thank you very much for the detailed reply. >> Based on your information I deduce: >> >> 1) Using gcc 4.2 with 4.0 (c++) libraries is a supported >> configuration by Apple > > Right. > >> I then conclude that the C++ ABI is fully compatible between 4.0 and >> 4.2 > > Right. [snip, then user hypothesizes as to why there are problems with boost under gcc 4.2/libstdc++ 4.0 on current Apple systems] >> This is the case because boost assumes that a 4.2 compiler implies >> 4.2 libraries in flies such as boost/detail/atomic_count_gcc.hpp: >> >> #if (__GNUC__ > 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 2)) >> # include <ext/atomicity.h> >> #else >> # include <bits/atomicity.h> >> #endif > > Yes, this is a bug or faulty assumption in boost. [snip] > The 4.2 library issue is a bug in Boost, not a problem with > our compiler. I'd suggest raising the issue on one of the boost > mailing lists and see what they say. Comments? Mat

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