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[safe_numerics] questioning the basic idea
by Andrzej Krzemienski 15 Dec '14

15 Dec '14

Hi, I was going through the Safe Numerics library in Boost Library Incubator, and I realized I disagree with the basic idea it is built on. I wanted to rise my concerns here. If I were to summarize in one sentence what this library is, I would say: a drop-in replacement for type int that checks for overflow in run-time and throws an exception if it finds one. Did I get it right? The remainder of this post is based on this interpretation. If so, I am not sure if this idea is a good one and worth promoting in Boost. BTW this is one of my criteria for letting a library into Boost: whether it promotes worthy ideas. I agree with the statement that a program should be UB-free. But I do not think that the approach of letting the programmer do what he did before, having the library or some run-time tool check for potential UB, and throwing an exception instead makes the program any better (or safer). It is just hiding the symptoms but not curing the disease. The programmer should not plant the UB in the first place - I agree. But this is different than first doing the mess and then having the run-time clean it up for you. I know it works for many people, in a number of languages, and it may even be considered a practical solution, but (by inclusion into Boost) I wouldn't like to be sending the message "this is how you are suppose to code". I try to recall how I use type int. I do not think I ever use it for anything that would be close to "numeric" as I know the term from math. Use Case 1 (an index): for (size_t i = 0, I = v.size(); i != I; ++i) { if (i != 0) str += ","; str += v[i]; } There doesn't appear to be a good reason to wrap it into safe<int> here, even though the incrementation could possibly overflow. Plus, it would kill my performance. Use Case 2 (using reasonably small range): I used an int to represent a square on a chessboard. There is only 64 squares, so I couldn't possibly overflow, on whatever platform. And even if there exists a platform where 64 doesn't fit into an int, I would not use safe<int> there. I would rather go for something like double_int. If I were to use some numeric computations on integers and I perceived any risk that I may overflow, I would not be satisfied with having the computations stop because of an exception. I would rather use a bigger type (BigInt?). I do not think int is even meant to be used in numerical computations. I believe it is supposed to be a building block for building more useful types like BigInt. One good usage example I can think of is this. After a while of trying to chase a bug I comae up with a hypothesis that my int could be overflowing. I temporarily replace it with safe<int> and put a break point in function overflow() to trap it and support my hypothesis. I would probably use a configurable typedef then: #ifndef NDEBUG typedef safe<int> int_t; #else typedef int int_t; #endif But is this the intent? But perhaps it is just my narrow perspective. Can you give me a real-life example where substituting safe<int> for int has merit and is not controversial? I do not mean the code, just a story. Regards, &rzej

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[endian] Heads up: breaking name changes coming
by Beman Dawes 15 Dec '14

15 Dec '14

Boost.Endian develop branch is about to have major changes merged in as part of the preparation for a mini-review. AFAICR, the breaking changes are limited to header, class, and function name changes, but there are a lot of hopefully non-breaking changes so I could easily be wrong about that. If you are currently using Boost.Endian develop branch, you will need to change your code accordingly. It would make sense to wait a few days until the mini-review merge is complete and any fixes required by regression test failures are fixed. Thanks for your patience, --Beman

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Re: [boost] List of C++ 11 only Boost libraries and their status?
by Dave Gomboc 14 Dec '14

14 Dec '14

On Sat, Dec 13, 2014 at 08:37 AM, Rogerio dos Santos <rogerio.santos.main(a)gmail.com> wrote: > > On Sat, Dec 13, 2014 at 8:27 AM, Nat Goodspeed <nat(a)lindenlab.com> wrote: >> >> I'm just contradicting the assumption that those who must work with >> old compilers aren't doing any new development, or have no interest in >> new libraries. >> > > To add to this point, I would like to mention that even new developments > trends might require support to old or limited compilers. E.g.: IoT, real > time projects, industrial HMIs and mobile applications. > > Roger Indeed. I work on embedded, real-time industrial control systems in a field where certain specifications (unfortunately, IMO) severely restrict the platform choices available. In many cases, the systems developed must be built using pre-C++98 compiler technology. While that is a problem I am attempting to address, I suspect it is going to take at least another year to do so, and I am confident that at least one of the platforms will probably never support multi-threading even if its vendor does end up improving or replacing its toolchain (and I have no iron-clad guarantee from the vendor that the toolchain will actually be improved or replaced, though I have a reasonable hope). None of the above constraints imply that the libraries developed by Boost are not of use for these systems, or that we are not interested in using Boost libraries to the extent that it is possible to do so. I think it is possible to structure compatibility code so that it doesn't egregiously interfere with future development. I always get nervous when Steve posts asking to hack away the support for a few more of the older toolchains. While I fully appreciate that his end-goal is well-intentioned, there's still important code out there relying upon some of those pre-C++98 workarounds that can still benefit from the fixes and new libraries introduced into new versions of Boost. Consequently, I'm much in favour of allowing Boost library maintainers who wish to retain support for older compilers the latitude to do so. Dave

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List of C++ 11 only Boost libraries and their status?
by Niall Douglas 13 Dec '14

13 Dec '14

For C++ Now 2015 I am intending to present an overview of C++ 11 only Boost libraries in the review queue or very near the review queue by the time of the conference. I'd appreciate help filling in missing gaps in this list: * Boost.Spirit X3 ETA to Boost review: unknown, last commit was June 2014. * Boost.Proto 0x ETA to Boost review: unknown, last commit was Oct 2013. * Boost.Hana ETA to Boost review: Summer 2015, last commit was today. * Boost.AFIO ETA to Boost review: Already in review queue, last commit was two days ago. * Boost.BindLib ETA to Boost review: Q1 2015, last commit was two days ago. * Boost.Spinlock ETA to Boost review: Q2 2015, last commit was four days ago. * Boost.KernelAlloc ETA to Boost review: Q1 2015, last commit was today. * Boost.Expected ETA to Boost review: no later than Summer 2015 probably much earlier, last commit was two weeks ago. * Boost.CRUX ETA to Boost review: hopefully by end of 2015, last commit was three days ago. I have to admit surprise at how long the list I have collected already is. Are there any other C++ 11 only Boost libraries I am missing, or have I got the ETAs wrong? Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

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New Feature, MathString.
by Jakub trzciński 13 Dec '14

13 Dec '14

Hi. My name is Jacob and i am new here.i have idea for new feature in boost. Actually i write a little library whitch name MathString. As you see by name the library will be calcule Row's from string. But it's not all. I was write a interface which add own Mathematical functions for row and variables. If you accept my idea i will send whole code. Code for example MathString test("sqrt(x,2)"); test.LinkFunction(&sqrt,"sqrt"); test.pushVariable("x",4); cout<<test.getResluts(); This code will be return 2 (as you know root with level 2 of 4 equals 2)

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C++ Concept-based tag dispatching using the Tick library
by pfultz2 13 Dec '14

13 Dec '14

Hello Everyone, For those interested. I added support for tag dispatching in the Tick. The reason it wasn't added earlier was concern over specialization. So now as a simple example, the `advance` function could be implemented like this: TICK_TRAIT(is_incrementable) { template<class T> auto requires_(T&& x) -> tick::valid< decltype(x++), decltype(++x) >; }; TICK_TRAIT(is_decrementable, is_incrementable<_>) { template<class T> auto requires_(T&& x) -> tick::valid< decltype(x--), decltype(--x) >; }; TICK_TRAIT(is_advanceable, is_decrementable<_>) { template<class T, class Number> auto requires_(T&& x, Number n) -> tick::valid< decltype(x += n) >; }; template<class Iterator> void advance_impl(Iterator& it, int n, tick::tag<is_advanceable>) { it += n; } template<class Iterator> void advance_impl(Iterator& it, int n, tick::tag<is_decrementable>) { if (n > 0) while (n--) ++it; else { n *= -1; while (n--) --it; } } template<class Iterator> void advance_impl(Iterator& it, int n, tick::tag<is_incrementable>) { while (n--) ++it; } template<class Iterator> void advance(Iterator& it, int n) { advance_impl(it, n, tick::most_refined<is_advanceable<Iterator>>()); } Now, specialization is still supported in a sane way. As an example, say there was an iterator called `foo_iterator` that fulfilled the type requirements for `is_incrementable`, `is_decrementable`, and `is_advanceable`, but it had an incorrect `+=` operator on it(perhaps it crahsed at runtime). So `is_advanceable` can be specialized to prevent this problem: template<> struct is_advanceable<foo_iterator> : std::false_type {}; Even though it is specialized to false, it can still dispatch to `tag<is_decrementable>` and `tag<is_incrementable>` tags. You can read more about it here: http://pfultz2.github.io/Tick/doc/html/tag/ Any feedback is appreciated. Thanks, Paul Fultz II -- View this message in context: http://boost.2283326.n4.nabble.com/C-Concept-based-tag-dispatching-using-th… Sent from the Boost - Dev mailing list archive at Nabble.com.

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Duration of formal reviews
by Vladimir Prus 12 Dec '14

12 Dec '14

Some time ago we had a poll about formal reviews problems: https://plus.google.com/u/0/+VladimirPrus/posts/5spgjicc3fv The majority said that ten days are not enough. Of course, it's not very statistically significant, but that's the only data we've got, and we have a rather sparse schedule. How about trying two weeks for a formal review? Thanks, -- Vladimir Prus CodeSourcery / Mentor Embedded http://vladimirprus.com

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Is Boost.Xpressive's sregex::compile() thread-safe for an object only used in that thread?
by Chambers, Matthew 12 Dec '14

12 Dec '14

I have a case where I am compiling a dynamic regex based on client code input, and it works except for when I run my multi-threaded unit test 100-1000 times. When I run it with 1 thread, it never fails. When I run it with 2 or 4 threads it fails at this rare frequency. Except on my build server, where it seems to fail most of the time, which is how I learned about the issue to begin with. It's not crashing though, it's just very rarely returning the wrong results, and not always in the same place in the unit test. So I'm trying to understand Xpressive's thread safety. I understand it as far as not using a regex object in multiple threads until it's finished compiling and not sharing a match_results across threads, but what about compiling different regex objects for each thread: if two threads are compiling two different regexes (or even the same const regex string but from different threads, which is possible with my test code), is that ok? I'm seeing this failure on MSVC 12 but I think I also got it with VC10, just not as reliably on the build server (but the build server had to be upgraded to Windows 2012 to install VC12, so maybe that OS change had an effect as well). Thanks, -Matt

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[coroutine] x86 msvc11 stack corruption
by Tobias Loew 12 Dec '14

12 Dec '14

Hi, I use Boost 1.55 uni-directional coroutines to build an x86 MSVC11 application. I have a simple pull-type (boost::coroutines::coroutine<void>::pull_type) that under certain reproducable conditions destroys the stack after returning from the coroutine. Here is the corrupted stack as shown by VS2012 > ebs2000.exe!CScriptMainFrame::DoRun(CPascalEditorDoc * 0x00000000, int 0x00000000, int 0x00000000) Line 3372 C++ ebs2000.exe!CScriptMainFrame::OnDebugStepover() Line 4916 C++ mfc110u.dll!_AfxDispatchCmdMsg(CCmdTarget *, unsigned int, int, void (void) *, void *, unsigned int, AFX_CMDHANDLERINFO *) C++ 00000002() Unknown [Frames below may be incorrect and/or missing] mfc110u.dll!CCmdTarget::OnCmdMsg(unsigned int, int 0x00000000, void *, AFX_CMDHANDLERINFO *) Line 364 C++ mfc110u.dll!CWnd::OnCommand(unsigned int 0x00018263, long 0x00000000) Line 2785 C++ mfc110u.dll!CFrameWnd::OnCommand(unsigned int 0x00018263, long 0x00000000) Line 389 C++ ... This only happens in windows x86 32-bit release-builds when the coroutine finishes upon a user-action that also includes a windows WM_SETFOCUS message on my menu-bar. If at least one of the following is true, the stack-corruption does NOT happen: - debug-build - x64 build - using a different pull-type, e.g. enum status_enum{...}; boost::coroutines::coroutine<status_enum>::pull_type - not returning form the coroutine, but pushing just before the end of the coroutine and swapping the pull-type-variable with a default constructed "not-a-coroutine" Even though I have a lot of workarounds, I still would like to know, why this happens. regards Tobias PS: I had to recompile ml /safeseh /c make_i386_ms_pe_masm.asm ml /safeseh /c jump_i386_ms_pe_masm.asm to get SAFESEH-libraries. -- View this message in context: http://boost.2283326.n4.nabble.com/coroutine-x86-msvc11-stack-corruption-tp… Sent from the Boost - Dev mailing list archive at Nabble.com.

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[review] Last day for formal review for Sort library
by Edward Diener 12 Dec '14

12 Dec '14

Today is the last day for the formal review of the Sort library by Steven Ross, which started November 10. We have had some great discussions and reviews so far and I would like to thank everybody involved, but as always we need more formal reviews. If you need any delay for your review after today, please contact me at 'eldiener at tropicsoft dot com' and I will take your review into account if given within a reasonable period of time after today. About the Sort library ================== The Sort library is a library which implements hybrid sorting algorithms based on a Spreadsort ( http://en.wikipedia.org/wiki/Spreadsort ), of which the author of the library, Steven Ross, is the inventor. The algorithm provides a sort that is faster than O(n*log(n)). The library provides a generic implementation of high-speed sorting algorithms that outperform those in the C++ standard in both average and worst case performance. These algorithms only work on random access iterators. They are hybrids using both radix and comparison-based sorting, specialized to sorting common data types, such as integers, floats, and strings. These algorithms are encoded in a generic fashion and accept functors, enabling them to sort any object that can be processed like these basic data types. Where to get it =============== The library is available on github at https://github.com/spreadsort/sort. The library is in modular Boost format and can be cloned to libs/sort under your local modular boost directory. I have provided as the review manager online documentation at: http://eldiener.github.io/sort Review guidelines ================= Reviews should be submitted to the developer list (boost(a)lists.boost.org) preferably with '[sort]' in the subject. Or if you don't wish to for some reason or are not subscribed to the developer list you can send them privately to me at 'eldiener at tropicsoft dot com'. If so, please let me know whether or not you'd like your review to be forwarded to the list. For your review you may wish to consider the following questions: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should attempt to answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Even if you do not wish to give a full review any technical comment regarding the library is welcome as part of the review period and will help me as the review manager decide whether the library should be accepted as a Boost library. Any questions about the use of the library are also welcome.

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