August 2004 - Boost-users - lists.boost.org

RE: [Boost-users] Re: Guidelines for effective exception usage
by Mark Storer 26 Aug '04

26 Aug '04

> No it is not. Even if you aren't throwing due to memory starvation, > you could run out of memory during unwinding, when the exception is > copied. That leads you directly to terminate(). Do not pass Go; do > not collect $200. Venturing a little far afield, but one technique I've heard of is to grab a block, so you can release it in low-memory situations (or just every time you throw). This ensures (in theory) that you'll have enough memory to copy your exception, create your strings, and so on. If you manage to recover, you just grab another block ("prime the pump") and soldier bravely forward. Given STL's habit of allowing people to specify an allocator, you could even go so far as to build a custom allocator that worked on some pre-allocated block of memory for your exceptions (strings, vectors, whatever you deem necessary). Either way, you'll run out of memory a little earlier (not a big issue in many environments), but you _will_ get to pocket the $200. It's not hard to imagine an environment where grabbing a couple extra Kb would be a Bad Thing, but I'd think this trick would be fine on PCs and the like. --Mark Storer Senior Software Engineer Verity, Inc.

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Generative Programming book
by Samuel 26 Aug '04

26 Aug '04

The ISBN for the "Generative Programming" book is wrong. 0-210-30977-7 is incorrect 0-201-30977-7 is correect That book is used and described in the Boost "Feature Model Diagrams in text and HTML" page. Also, the Generative Programming web site isn't working for me, but perhaps the problem is only temporary. Note that I am not asking for help with any of that. I obviously already know what the correct ISBN is. I am posting this in case it helps others; the web page needs to be updated for the ISBN at least. The Boost "What to do about Boost bugs" page says to submit "a bug report to either boost-users list, boost mailing list, or our bug tracking facility at SourceForge" and that "either of the mailing lists is a preferred way". However it does not describe what a bug report is. If there is not a formal format, then I hope the above is adequate.

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/usr/include/boost/mpl/if.hpp:75: internal compiler error: Segmentation fault
by Nils Wagner 26 Aug '04

26 Aug '04

Dear experts, I am going to install VPython http://www.vpython.org/linux_download.html on SuSE 9.1 which makes use of the boost library. However I got a segmentation fault. /usr/include/boost/mpl/if.hpp:75: internal compiler error: Segmentation fault Please submit a full bug report, with preprocessed source if appropriate. See <URL:http://www.suse.de/feedback> for instructions. Preprocessed source stored into /tmp/ccrXaXyw.out file, please attach this to your bugreport. Any pointer would be appreciated. Nils

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Boost Build, custom-built targets
by John Meinel 26 Aug '04

26 Aug '04

Hello all- I'm currently using Boost Build v1 for some of my projects. I must say, it's significantly better than Makefiles. Overall, I'm quite pleased, though it took a little while to learn. I haven't been able to figure out one thing, though. How to generate custom built targets. Basically, I want to auto-generate a C++ source file so that I can keep track of version information. I have a python script that determines the version information from various sources (such as the revision control system [arch]), and I would like it to be run before my library is built. If I was using a makefile I would do something like this: .PHONY: version.cpp version.cpp: generate_version.py version ./generate_version.py This would cause version.cpp to be generated fresh each time the build process was called. However, I don't really need the ".PHONY", it would be okay if it was only created whenever one of the other files changed. I'm sure it's possible to do this with bjam, I just haven't figured out how to do customized stuff like this yet. Thanks, John =:-> PS> Is there a better mailing list for this?

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RE: [Boost-users] Re: Guidelines for effective exception usage
by Ben Hutchings 25 Aug '04

25 Aug '04

Peter Dimov <pdimov(a)mmltd.net> wrote: > Ben Hutchings wrote: > > Peter Dimov <pdimov(a)mmltd.net> wrote: > >> Victor A. Wagner Jr. wrote: > >>> > >>> OK, blunt point. > >>> the standard is (insert favorite expletive or "in error") if it > >>> allows use of std::runtime_error to terminate the program due to > >>> low memory situations (run out of memory (due to copying) during > >>> stack unwinding). > >> > >> It does not allow such a thing. > > > > This is an known and unresolved issue: > > http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#254 > > "The copy constructors of all exception-derived classes already have > a no throw spec. Reference 18.6.1, 19.1 and 15.4/13." "As they stand, the copy constructors might fail via a call to unexpected. I think what is intended here is that the copy constructors can't fail." (Is it really necessary for us to quote the referenced text at each other? This is silly.)

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RE: [Boost-users] Re: Guidelines for effective exception usage
by Ben Hutchings 25 Aug '04

25 Aug '04

Peter Dimov <pdimov(a)mmltd.net> wrote: > Victor A. Wagner Jr. wrote: > > > > OK, blunt point. > > the standard is (insert favorite expletive or "in error") if it > > allows use of std::runtime_error to terminate the program due to low > > memory situations (run out of memory (due to copying) during stack > > unwinding). > > It does not allow such a thing. This is an known and unresolved issue: <http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#254>

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Update: exception class that
by Stephen torri 25 Aug '04

25 Aug '04

I thought I would share what I am using for exceptions given the excellent advice from everyone responding to my initial email. There is no usages of any memory allocation or std::string like variables. If there are any 'oops' or 'gotchas' please let me know. My plan is to use a command flag for taking into a value. The value will determine what debug messages are reported at the cause of the problem. The message will be displayed via std::cerr. Stephen ---------------- Header ---------------- #ifndef IO_EXCEPTION_H_ #define IO_EXCEPTION_H_ #include <exception> #include <inttypes.h> namespace kurt { /*! * \class IOException * \brief Rather than inheriting from ifstream this class delegates * any required functionality to it. * \date 2003 * \author Stephen Torri */ class IO_Exception : public virtual std::exception { public: IO_Exception (uint32_t message_id); /*! * \brief Destructor */ virtual ~IO_Exception (void) throw(){} /*! * \brief Return the extra message accompanying the exception. */ const char* what (void) const throw(); /*! * \brief Return tne name of the exception */ const char* name (void) const throw(); enum { CANNOT_OPEN, INPUT_CORRUPTED, INVALID_IO_OP, READ_ERROR, UNSUPPORTED_OP, WRITE_ERROR, }; private: static const char* m_exception_name; static const char* m_messages[]; uint32_t m_id; }; } /* namespace kurt */ ------------- Source ------------- #include "IOException.hpp" namespace kurt { const char* IO_Exception::m_exception_name = "IO_Exception"; const char* IO_Exception::m_messages [] = { "I/O Error: cannot open", // CANNOT_OPEN "Input data is corrupted", // INPUT_CORRUPTED "Invalid i/o operation attempted", // INVALID_IO_OP "Error reading input", // READ_ERROR "Unsupported I/O operation", // UNSUPPORTED_OP "Error writing output", // WRITE_ERROR }; IO_Exception::IO_Exception (uint32_t message_id) : std::exception(), m_id(message_id) {} const char* IO_Exception::what (void) const throw() { return m_messages[m_id]; } const char* IO_Exception::name (void) const throw() { return m_exception_name; } } /* namespace kurt */ #endif /* IO_EXCEPTION_H_ */ -- Email: storri(a)torri.org

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MPL vector size limit
by Arkadiy Vertleyb 25 Aug '04

25 Aug '04

Hi, Can BOOST_MPL_LIMIT_VECTOR_SIZE be increased beyond 50, and if yes, what is involved in this? Thanks, Arkadiy

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licenses...
by MarC 24 Aug '04

24 Aug '04

Hi I subscribed to this list to find out if I can publish one program containig "Boost Filesystem Library" under the GPL2. I saw that Boost license is even more flexible than the GPL2 but I'm not sure if I can release a program containing Boost with GPL2... anybody knows? where should I ask to answer my question? my case is that I'm developping a stand-alone console program which I want to integrate in other GPL licensed projects of web developpment like quanta.sourceforge.net or screem.sourceforge.net. I don't mind about modifying the licene of my program to adapt it to the special license of "Boost Filesystem Library" but I think it's inaffordable to modify all licenses of big projects like quanta or screem... so I'm a little bit confused. any idea? thanks in advance!

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boost.graph build problem in latest anonomous CVS update.
by Jeff Holle 24 Aug '04

24 Aug '04

I've just refreshed my boost via CVS and ran into a build problem with gcc v3.4.1. Initially, seems like everything failed on my system. However, I discovered that there is now a configure option :-) . After installing user.hpp where it does some good stuff, the bjam of the root of boost succeeded. However, in running bjam in $ROOT_BOOST/libs/graph/build. This Jamfile is configured to build both release and debug version of bgl-viz. It fails with similiar problems that I was getting elsewhere before I ran configure. An example of the problems is: boost/config/stdlib/libstdcpp3.hpp:33: error: expected unqualified-id before '<<' token boost/config/stdlib/libstdcpp3.hpp:33: error: expected `,' or `;' before '<<' token

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