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Boost configure options for crosscompilation ?
by MikeW 20 Nov '06

20 Nov '06

I would like to crosscompile Boost under Buildroot. I created what appeared to be a successful package file, but found that the native compiler and tools were used rather that Buildroot's crosscompiler toolchain. However, I could not see any other 'configure' options to switch to using a crosscompiler (EPREFIX looked promising at first but seems to be a path prefix, rather than a tool prefix such as "arm-linux-"). I note an earlier post (unable to post a 'follow-up' to it) seemed to successfully do a cross build. Could you tell me how Boost is 'configure'd to use the crosstools rather than the native tools ? Thanks, Mike

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Beginner's shared_ptr question...
by Martin Waller 20 Nov '06

20 Nov '06

(g++ 3.3.5, boost 1.32) I have a program as follows: Header: //multiple include guard omitted for clarity #include <boots/shared_ptr> class someOtherClass; class MyClass { public: MyClass(); void init(); . . . private: boost::shared_ptr <someOtherClass> spOther; . . . }; Implementation #1: #include <MyClass.hpp> #include <someOtherClass.hpp> MyClass::MyClass() { init(); } void MyClass::init() { spOther(new someOtherClass(this)); } Implementation #2: #include <MyClass.hpp> #include <someOtherClass.hpp> MyClass::MyClass():spOther(new someOtherClass(this)) { } Question: Why does implementation #2 fail to compile with the error: error: no match for call to '(boost::shared_ptr<someOtherClass>)(someOtherClass*)' ? yet implementation #2 compiles fine? Please help me understand what going on here...is it possible to get implementation #2 to compile or is it 'bad code'? Thanks

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How to use bind with explicit constructor conversion?
by Terry G 20 Nov '06

20 Nov '06

This doesn't compile. How best to accomplish this using generic STL or Boost algorithms/adapters? terry #include <iostream> #include <iomanip> #include <algorithm> #include <vector> #include <iterator> #include <cstdlib> #include <boost/bind.hpp> #include <boost/mem_fn.hpp> using namespace std; using namespace boost; class MyInt { int _value; public: explicit MyInt(int x=0) : _value(x) { } int value() const { return _value; } }; // MyInt int main() { vector<MyInt> v; // Do this: // for (int i=0; i!=30; ++i) v.push_back(MyInt(rand())); generate_n(back_inserter(v), 30, bind(MyInt, bind(rand))); // Now print v. transform(v.begin(), v.end(), ostream_iterator<int>(cout, "\n"), mem_fn(&MyInt::value)); return 0; } // main

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boost::numeric::ublas::matrix adaptors for C style arrays
by Edward Grace 20 Nov '06

20 Nov '06

Dear All, Is it possible to adapt e.g. a pointer to double in to a ublas::matrix<double>, or construct a matrix from a pointer to double? I have used the Blitz++ libraries, with those it is possible to use storage allocated elsewhere. This is to allow the painless interface of my code with legacy C code. I would like to do something like the following: using namespace boost::numeric::ublas; double *p; p = new double[100]; .... Fill p[*] with data // Construct a 10x10 matrix using externally allocated storage. matrix<double> A(10,10,p); There does appear to be a hint that I can use my own allocator, but it is far from clear how I go about doing this. For example coming up with an Allocator function that doesn't allocate but instead uses existing memory. class MyAllocator : public GeneralAllocator { double *TheMemory; public: MyAllocator(double *p) { TheMemory = p; } allocate() {} }; matrix<double,MyAllocator> A; Failing that, I'd like an adaptor that allows me to effectively do something like: matrix<double> A; double *p; // Allocate p and fill with stuff! A = adaptor<matrix<double> >(p,nCol,nRows); A is now a 10x10 matrix<double> using the memory pointed to by p. Obviously there are issues regarding who is now responsible for this memory, something handled by the memory policy in Blitz++ (neverDelete, etc). Help!! Is there a way to do this? -ed

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[Boost.General] Improvement proposals for boost data access
by Markus Werle 20 Nov '06

20 Nov '06

Hi Boosters! While trying to trace the development of some boost libraries I see opportunities for improvement concerning the boost data distribution system. I am a little bit tired of looking up 3 or 4 different places in order to find out how some code snippet or library part under development is distributed, whether it is commited to the sandbox cvs, the vault, or stored hidden below boost-consulting.com (like SummerOfCode stuff with only a mailing list post pointing to it) or whether the developer has deliberately choosen to set up his own cvs/svn tree or other distribution method e.g. via sourceforge (which might be perfectly OK, Joel!). Yet I am missing the single entry point to all these GoodThings. Things are suboptimal: Example 1: Try to find out via boost web pages where one can download the latest and greatest version of boost::fusion. You can find a version at http://spirit.sourceforge.net/, but I am unsure if it is the latest bleeding edge version ... Example 2: Function types is under review. The files are accessible via tinyurl, so boost ML content is not self-contained. If I look at it in 6 years (when <your favorite .com monster here> bought tinyurl and crashed the database), I will not be able to find any hint to where to find the files. Also if I'd like to see how that lib looked like at the time of review in order to understand the review discussion on the mailing list I am out of luck. Example 3: files in the vault are rather volatile, no file history available. Still waiting to obtain some old files mentioned in some post ... I'd like to make proposals for improvement: 1. Rule: Libraries under review _must_ be commited to cvs/svn tree of boost or boost-sandbox. In order to help people behind firewalls and resistent IT administrators, a script creates daily snapshots of cvs/svn tree which are accessible via ftp/http from boost.org similar to the way gcc is distributed. If a developer has no access via cvs/svn he/she has to find someone who can take this task (or boost has a server which provides svn on port 80 ...) Any announcement concerning reviews points to the ftp/http access point and contains the cvs/svn command which has to be used in order to obtain the files. Rationale: KISS for users. Blindly trust to find the code at one single point. 2. Rule: Posts to boost ML which link to any code snippet or fileset uploaded to the vault for discussion use a http link to the true URL at boost::vault. Using the full link is declared as netiquette rule for posting to ML. Rationale: Internet data is not persistent. A full link gives you the chance to find the file either by contacting the admin of the mentioned http server or by filename via standard search engines. 3. Technical measure: The vault is under some automatic version control (http://subversion.tigris.org/faq.html#filesystem http://noedler.de/projekte/wdfs/ http://svnbook.red-bean.com/en/1.1/apcs03.html) and versions can be retrieved via http on a per date basis, which allows to follow older discussions easily. Rationale: I recently read a discussion between Jeremy S., Joel d. G. and Dave A. which was hard to follow anyway due to the subject and due to the skill level of those who were talking. It would be much easier to get at least some minimal insight into what they were talking about if the files were still available (so I hope). Sometimes it really helps to read early stage code that is not yet polluted by all this CIRCUMVENT_BROKEN_COMPILER macros. [sidenote: looking forward to the new book: "The design and evolution of boost::mpl, boost::fusion, boost::graph and 12 other libraries" including all the chapters Dave and Alex left out in their first book ;-P] What do you think? Markus

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[Filesystem]: Is an empty path relative or complete?
by Michael Partridge 20 Nov '06

20 Nov '06

Hi Boosters, I'm using the filesystem::complete function and have the following situation: bfs::path my_path(""); bfs::path current = bfs::current_path(); bfs::path p = bfs::complete(my_path, current); This results in p.string == "". Now I can see from the code that if my_path.empty() == true then a copy of my_path is returned, but I'm not certain of the rationale behind this. If I pass in an empty path and ask for it to be turned into a complete path then shouldn't I just get the base? As an additional consideration, if I go: bfs::path p = system_complete(bfs::path("")); Shouldn't I get current_path(), rather than an empty path ""? Cheers, Michael ps. sorry if this question has been answered before, I searched the archive and couldn't find any discussion.

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[Serialization] NVP and xml archives
by michael mathews 19 Nov '06

19 Nov '06

Hi All, I have a class that contains a list of name value pairs . I would like the serialization to use the names for the tag names in the xml archive. Is there a way to do this or do I need to write my own custom archive? Thanks in advance Michael __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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[test] build problem/regression with RC_1_34_0
by Chris Hoeppler 18 Nov '06

18 Nov '06

Hi, With last weekend's cvs version of RC_1_34_0 is was able to use the dynamic-library version of the unit_test_framework. Since I did a cvs update yesterday I get a link error trying to do so: g++ -o build/debug/test/kern/test_macros.o -c -g -Wall -ftemplate-depth-255 -O0 -fno-inline -DBOOST_TEST_DYN_LINK -I. -I/home/hoeppler/src/boost_RC_1_34_0 test/kern/test_macros.cpp g++ -o build/debug/test/kern/test_macros -Wl,-rpath-link,. build/debug/test/kern/test_macros.o build/debug/src/kern/parser/macros.o -L/home/hoeppler/src/boost_RC_1_34_0/stage/lib -lboost_filesystem-gcc41-d -lboost_regex-gcc41-d -lboost_unit_test_framework-gcc41-d /usr/lib/gcc/i586-suse-linux/4.1.0/../../../crt1.o: In function `_start': init.c:(.text+0x18): undefined reference to `main' collect2: ld returned 1 exit status Addidtional information: This is gcc-4.1.0 on linux. The boost libs were built with the boost build system. I am setting up test_suits as follows: test_suite* init_unit_test_suite( int, char* [] ) { test_suite* test(BOOST_TEST_SUITE("Unit test macros")); // <snip> return test; } Any idea what's going wrong? Thanks Chris

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[iterator] std::distance ignores random_access_traversal_tag
by Markus Werle 18 Nov '06

18 Nov '06

Hi! This was detected by profiling. I expected the code below to have a rather cheap std::distance call because my iterator was tagged as random_access. gcc-4.0.3 (cygwin) and VC8 IMHO choose the wrong std::distance algorithm, but why? The stuff compiles even when distance_to is not defined. Maybe I misunderstood the docs, especially the passage <cite url="http://boost.org/libs/iterator/doc/iterator_facade.html"> [...] where iterator-category is defined as follows: iterator-category(C,R,V) := if (C is convertible to std::input_iterator_tag || C is convertible to std::output_iterator_tag ) return C else if (C is not convertible to incrementable_traversal_tag) the program is ill-formed else return a type X satisfying the following two constraints: [..] </cite> Please explain and fix the code below. Markus #include <boost/iterator/iterator_facade.hpp> #include <boost/bind.hpp> #include <cstddef> #include <iterator> #include <iostream> template <typename ValueT, typename SizeT, typename IndexOperatorT> class signal_iter : public boost::iterator_facade <signal_iter<ValueT, SizeT, IndexOperatorT>, ValueT, // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! boost::random_access_traversal_tag, ValueT, SizeT> { public: typedef signal_iter<ValueT, SizeT, IndexOperatorT> my_own_t; inline signal_iter(IndexOperatorT IndexOperator, SizeT index) : m_IndexOperator(IndexOperator) , m_index(index) {} // quick and dirty with a dangling reference :-( inline signal_iter() : m_IndexOperator(IndexOperatorT()) , m_index(0) {} inline SizeT index() const { return m_index; } private: friend class boost::iterator_core_access; inline void increment() { ++m_index; } inline void decrement() { --m_index; } inline void advance(SizeT i) { m_index += i; } inline SizeT distance_to(signal_iter const& other) const { return other.index() - m_index; } inline bool equal(signal_iter const& other) const { return (other.index() == m_index); } inline ValueT dereference() const { return m_IndexOperator(m_index); } protected: IndexOperatorT m_IndexOperator; SizeT m_index; }; // stripped down demo class Demo { static const std::size_t mysize_ = 20; typedef std::size_t size_type; typedef double value_type; double data_[mysize_]; public: double operator[](std::size_t i) { return data_[i]; } typedef boost::_bi::bind_t <double, boost::_mfi::mf1<double, Demo, unsigned int>, boost::_bi::list2<boost::_bi::value<Demo*>, boost::arg<1> > > bind_type; typedef signal_iter<const value_type, size_type, bind_type> const_iterator; const_iterator begin() { return const_iterator (boost::bind(&Demo::operator[], this, _1), 0); } const_iterator end() { return const_iterator (boost::bind(&Demo::operator[], this, _1), mysize_); } }; int main() { Demo demo; std::cout << std::distance(demo.begin(), demo.end())<< std::endl; }

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[Boost.Asio] Watching over a socket descriptor
by Memfis 18 Nov '06

18 Nov '06

I have an external communications library (Linux), which exposes a set of high-level APIs and a socket descriptor for me to watch over (as in select()). If there is something waiting on the socket, I am to call a function from the library that will read the data, construct some structures from it and return them. My question is if and how can I integrate this into Boost.Asio, so that I could handle connections created using Boost.Asio and the external library with the same code (to the point of actually reading some data)? -- Memfis

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