November 2013 - Boost - lists.boost.org

[IdentityType] Const omission undocumented.
by Mostafa 03 Dec '13

03 Dec '13

#include <boost/utility/identity_type.hpp> #include <utility> int main() { BOOST_IDENTITY_TYPE(( std::pair<int,int> const )) x; // This compiles, so the const qualification in the // above macro parameter is ignored. x = std::make_pair(0,1); return 0; } The omission of const qualification in BOOST_IDENTITY_TYPE types is undocumented. This omission maybe deduced from the documented implementation, but, as noted, that is not part of the library api and is subject to change. I therefore propose that this behaviour be documented as part of the library's public api. Mostafa

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Subversion repository closed for all commits on all branches
by Beman Dawes 02 Dec '13

02 Dec '13

The Subversion repository is now closed for all commits on all branches. An attempt to commit will fail a pre-commit hook, resulting in the following error message: Command: Commit Modified: C:\boost\trunk\libs\system\doc\index.html Sending content: C:\boost\trunk\libs\system\doc\index.html Error: Commit failed (details follow): Error: Commit blocked by pre-commit hook (exit code 1) with output: Error: This Subversion repository is no longer in active use. Error: Error: It has been superseded by a Git super-project repository Error: and individual Git repositories for each Boost library. Error: Error: See: https://github.com/boostorg Completed!: The next step in the conversion to Git and Modular Boost is to run the conversion script one last time, and then turn it off. We will let you know when that is completed. -- The Release Managers

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[conversion] Isolating the phantom file changes problem
by Beman Dawes 01 Dec '13

01 Dec '13

This is the simplest case I could come up with where git clone produced a initially modified state. Any ideas why this is happening? Is this another manifestation of crlf problems? --Beman D:\modular-boost\libs\intrusive>git clone --recursive git@github.com:boostorg/boost.git modular-boost ... much output, no apparent error messages... D:\modular-boost>git status # On branch master # Changes not staged for commit: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # (commit or discard the untracked or modified content in submodules) # # modified: libs/interprocess (modified content) # modified: libs/intrusive (modified content) # modified: libs/pool (modified content) # no changes added to commit (use "git add" and/or "git commit -a") D:\modular-boost>cd libs/pool D:\modular-boost\libs\pool>git status # Not currently on any branch. # Changes not staged for commit: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: doc/images/mb1.svg # modified: doc/images/mb2.svg # modified: doc/images/mb3.svg # modified: doc/images/mb4.svg # modified: doc/images/pc1.svg # modified: doc/images/pc2.svg # modified: doc/images/pc3.svg # modified: doc/images/pc4.svg # modified: doc/images/pc5.svg # no changes added to commit (use "git add" and/or "git commit -a") D:\modular-boost\libs\pool>cd ..\interprocess D:\modular-boost\libs\interprocess>git status # Not currently on any branch. # Changes not staged for commit: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: proj/vc7ide/managed_shared_memory.vcproj # modified: proj/vc7ide/offset_ptr_test.vcproj # no changes added to commit (use "git add" and/or "git commit -a") D:\modular-boost\libs\interprocess>cd ..\intrusive D:\modular-boost\libs\intrusive>git status # Not currently on any branch. # Changes not staged for commit: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: proj/vc7ide/avl_multiset/avl_multiset.vcproj # modified: proj/vc7ide/avl_set/avl_set.vcproj # modified: proj/vc7ide/sg_multiset/sg_multiset.vcproj # modified: proj/vc7ide/sg_set/sg_set.vcproj # modified: proj/vc7ide/splay_multiset/splay_multiset.vcproj # modified: proj/vc7ide/splay_set/splay_set.vcproj # no changes added to commit (use "git add" and/or "git commit -a")

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An open typeswitch using lambdas
by Sumant Tambe 30 Nov '13

30 Nov '13

Hi, I would like to get feedback on a small typeswitch library I've been working on for some time now. The library is designed to dispatch code (lambdas) based on the actual value of boost::any, boost::variant, and also general polymorphic hierarchies. An example is in order. template <class Poly> void test_poly(Poly& p) { match(p)( [](int i) { std::cout << "int = " << i << "\n"; }, [](double d) { std::cout << "double = " << d << "\n"; }, [](const std::string &s) { std::cout << "string = " << s << "\n"; }, [](std::ostream &o) { std::cout << "found ostream" << "\n"; } ); } int main(void) { std::ios_base &stream = std::cout; boost::any any(std::string("C++ Truths")); boost::variant<int, std::string> var("boost"); double d = 9.99; test_poly(stream); // prints found stream test_poly(any); // prints string = C++ Truths test_poly(d); // prints double = 9.99 test_poly(var) // prints string = boost } The implementation of the library is a little over 250 lines. Check it out here: http://coliru.stacked-crooked.com/a/72597a93b12916d4. clang is the only compiler I've been able to compile it with. It resembles Scala's match statement. Scala's match is way more powerful than what I've been able to achieve with C++ library emulation. It is also quite similar to Stroustrup's "Open and Efficient Typeswitch for C++" ( http://www.stroustrup.com/OOPSLA-typeswitch-draft.pdf) A quick benchmark shows that lambda-based typeswitch is about 4 to 5 times *slower*. If there is sufficient interest, I would be thrilled to contribute this library to boost. I believe it can be further generalized to support n-ary method dispatching. Thoughts? R/ Sumant

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[git] Line endings in bootstrap.bat on Windows
by Björn Pollex 29 Nov '13

29 Nov '13

I just cloned the modularized Boost repository from Github [1]. Right after the clone is done, git status gives me a complete diff on bootstrap.bat (so probably line endings). I do have autocrlf = true in my system configuration, so this shouldn't be the problem, right? Is anyone else seeing this? Am I doing something wrong? If so, how to do it correctly? Regards, Björn Pollex [1] https://github.com/boostorg/boost

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Is there a thin array wrapper/proxy lying around somewhere?
by Mostafa 29 Nov '13

29 Nov '13

(Yes, I'm aware of boost.array, boost.multiarray, and std::vector.) Is there any thin but complete array wrapper/proxy lying around somewhere in boost? A class that if substituted for an array will behave just like the substituted array? Thanks, Mostafa

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Re: [boost] [conversion] Enforcing tabs to spaces conversions and other git goodies.
by Cox, Michael 28 Nov '13

28 Nov '13

Michael On Thu, Nov 28, 2013 at 8:06 AM, Beman Dawes <bdawes(a)acm.org> wrote: > > On Thu, Nov 28, 2013 at 5:00 AM, Mateusz Loskot <mateusz(a)loskot.net> wrote: > > > On 28 November 2013 08:49, Cox, Michael <mhcox(a)bluezoosoftware.com> wrote: > > > In addition to re-normalizing the line endings, we could also start > > > enforcing coding standards, e.g. tabs converted to spaces standard via > > > gitconfig/gitattribute filters. Git allows you to define filters in your > > > .git/config or ~/.gitconfig file and specifying their use in > > > .gitattributes, e.g. in .gitconfig: > > > > > > # Convert tabs to 4 spaces (uses Linux expand/unexpand commands, so not > > > cross-platform) > > > [filter "tabspace"] > > > smudge = unexpand --tabs=4 --first-only > > > clean = expand --tabs=4 --initial > > > [...] > > > > ...automatically behind the scene? Scary! > > > > IMHO, this belongs to commit hooks. > > > > Qt's sanitize-commit may be a good example > > > > https://qt.gitorious.org/qt/qtrepotools/source/b69da7d675774be14027808328ea… > > > > Michael and Mateusz, > > Yes - sanitizing and commit hooks are important topics. But the way to > handle them is to start a new thread so that they don't get lost in the > line-ending bicycle shed discussion. > > Thanks, > > --Beman Mateusz, I agree hooks have to be used for the "golden" boostorg repositories since folks may forget to configure their local/public repositories with the appropriate hooks/filters, but if Boost goes fully distributed like Linux, there may be a lot of integration repositories a change flows through on it's way to boostorg and it's probably best to get the code normalized as soon as possible. Michael

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More flexible any_cast for boost::any
by DeadMG 28 Nov '13

28 Nov '13

Hello, I've been looking at ABIs and such (various unpleasant reasons). But I recently created the following code: #include <iostream> struct Base { virtual void check() = 0; template<typename T> T* IsDerivedFrom() { try { check(); } catch(T* p) { return p; } catch(...) { return nullptr; } return nullptr; } }; template<typename T> struct Derived : public Base { Derived(T obj) : t(obj) {} T t; void check() override final { throw &t; } }; struct A { virtual ~A() {} virtual void print() = 0;}; struct B : public A { int x; B(int y) : x(y) {} void print() override final { std::cout << x; } }; int main() { Base* b = new Derived<B>(B(5)); A* p = b->IsDerivedFrom<A>(); p->print(); } Whilst this is hardly the cleanest piece of code I've ever written, it also provides a base for implementing a more generic any_cast<ValueType>, which could succeed if ValueType is a base class of the stored type. Amazingly, the Standard requires the code to work but does not provide a cleaner means of implementation. I also note that, for some configurations, you could fall back to the Itanium ABI provided function directly, which would presumably be substantially faster and cleaner. Enabling this variety of any_cast would substantially improve the composability of boost::any. For example, it's arguable that std::function is merely boost::any but with additional interface requirements. With such an any_cast enhancement, it would be quite trivial to compose std::function implementations or similar concepts on top of boost::any.

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Re: [boost] [conversion] Isolating the phantom file changes problem
by Cox, Michael 28 Nov '13

28 Nov '13

In addition to re-normalizing the line endings, we could also start enforcing coding standards, e.g. tabs converted to spaces standard via gitconfig/gitattribute filters. Git allows you to define filters in your .git/config or ~/.gitconfig file and specifying their use in .gitattributes, e.g. in .gitconfig: # Convert tabs to 4 spaces (uses Linux expand/unexpand commands, so not cross-platform) [filter "tabspace"] smudge = unexpand --tabs=4 --first-only clean = expand --tabs=4 --initial Then in .gitattributes: # Code formats *.c text filter=tabspace *.cpp text filter=tabspace *.h text filter=tabspace *.hpp text filter=tabspace *.ipp text filter=tabspace *.tpp text filter=tabspace On a related topic, what is the svneol .gitattribute being used in the .gitattributes file do? I couldn't find it documented (I discovered the filter attribute while searching for the svneol attribute). Also, the mime type specified in a # comment following some attribute rule specification doesn't seem to be a supported syntax, i.e. the '#' has to be in the first column. Michael On Wed, Nov 27, 2013 at 3:02 PM, Gavin Lambert <gavinl(a)compacsort.com>wrote: > On 28/11/2013 05:17, Quoth Dave Abrahams: > > Another possibility might be to explicitly mark all text files in >>> .gitattributes with eol=lf and then run the conversion; I think that >>> would fix the repository blobs, >>> >> >> What goes into .gitattributes has no effect on the content of blobs in >> the repository. >> > > Sorry, when I wrote that I was envisaging the conversion process doing the > equivalent of an SVN checkout and then git add/commit. (And git commit > does take the attributes into account for eol conversion.) > > Since apparently it doesn't work like that, just ignore that suggestion. > > I still think that we need to renormalise the line endings though. Whether > that's done as a reconversion (fixing history) or just as an extra commit > (fixing current heads), that's up to you guys. ;) > > > > > _______________________________________________ > Unsubscribe & other changes: http://lists.boost.org/ > mailman/listinfo.cgi/boost >

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[conversion] Verification check results: svn trunk vs git develop
by Beman Dawes 28 Nov '13

28 Nov '13

* There is an entire library, Boost.Compose, long since deprecated and removed from svn in favor of Boost.Bind or Boost.Lambda, present in the git repos, both in master and develop. * Boost.Interprocess, git develop contains a header libs\include\boost\interprocess\fully_mapped_file.hpp that does not appear in the svn trunk head. * Boost.Type-Traits, git develop contains a header directory, \include\boost\detail, with two header files. Neither these two headers nor the directory are present in svn trunk head. * All 9974 headers in svn trunk/boost head have git super-project boost header entries generated by "b2 headers" and the content, ignoring end of line differences, is identical in all of them. * Exactly the same 5680 regression tests passed for both svn trunk head and git develop head. It doesn't get any better than that! --Beman

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