December 2013 - Boost - lists.preview.boost.org

[git] automated update of superproject master branch
by Peter A. Bigot 14 Feb '14

14 Feb '14

I realize there are several email threads about how the super-project branch should be managed, but most pre-date live experience with boost on git and go deep into other aspects of the issue, so I still want to call this out specially: https://svn.boost.org/trac/boost/wiki/ModBigPicture specifies that the master branch on each module should be stable at all times, which is the right policy. Currently, the master branch on the super-project is automatically updated twice(?) per hour selecting all updates to the master branches of modules. Consequently, super-project master is the exact opposite of stable. This divergence is confusing. I'm unconvinced that waiting a few days will demonstrate a significant decrease in churn on the super-project master branch. Some is due to multiple updates to specific modules, which might decrease as maintainers become more familiar with git and only push once, but interoperability issues will still arise and there will be no way to tell which master branch commits produce a working Boost installation. There is value in having a branch with automated-update semantics, but IMO regardless of what the final policy will be, "master" is not the right choice for this, and automated updates of it should stop ASAP. Perhaps the update script can simply be moved to occur on latest/master and latest/develop. Leave master untouched until whatever gets committed to it has undergone cross-toolchain integration validation, and make develop available for changes to superproject content that are not just submodule updates. Peter

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sqlpp11: SQL for C++
by Roland Bock 06 Feb '14

06 Feb '14

Hi, over the last four or five years I developed several SQL libraries for C++. With C++11 I was finally able to create an SQL library that meets my own expectations and requirements. It is being used in production, I recently put it on github, and I would really like to hear from you guys whether this is something that could be interesting for you personally or for boost? https://github.com/rbock/sqlpp11 https://github.com/rbock/sqlpp11/wiki sqlpp11 is a template library representing an embedded domain specific language (EDSL) that allows you to * define types representing tables and columns, * construct type safe queries checked at compile time for syntax errors, type errors, name errors and even some semantic errors, * interpret results by iterating over query-specific structs with appropriately named and typed members. This results in several benefits, e.g. * the library user operates comfortably on structs and functions, * the compiler reports many kinds of errors long before the code enters unit testing or production, * the library hides the gory details of string construction for queries and interpreting string based results returned by select calls. I.e. you don't need to use strings in query construction where you wouldn't use them in SQL and there is no need to use positional arguments or to parse strings when obtaining fields from a result row (the latter being true unless you do not know which columns to select at compile time). The library supports both static and dynamic queries. The former offers greater benefit in terms of type and consistency checking. The latter makes it easier to construct queries on the flight. Specific traits of databases (e.g. unsupported or non-standard features) are known at compile time as well. This way, the compiler can tell the developer at compile time if a query is not accepted by the database (e.g. if a feature is missing). And the library can form the query in the correct manner, for instance if the engine uses concat instead of operator|| to concatenate strings. Two Examples: ============= Static Select: -------------- // selecting zero or more results, iterating over the results for (const auto& row : db.run( select(foo.name, foo.hasFun) .from(foo) .where(foo.id > 17 and foo.name.like("%bar%")))) { if (row.name.is_null()) std::cerr << "name will convert to empty string" << std::endl; std::string name = row.name; // text fields are implicitly convertible to string bool hasFun = hasFun; // bool fields are implicitly convertible to bool } Dynamic Select: ---------------- auto s = dynamic_select(db, tab.foo).dynamic_columns().from(tab); if (userWantsBar) s.add_column(tab.bar); for(const auto& row : run(s)) { std::cerr << "row.foo: " << row.foo; if (userWantsBar) std::cerr << "row.bar" << row.at("bar"); std::cerr << std::endl; }; Please let me know your questions/thoughts/suggestions/rants. Contributions welcome, of course :-) Regards, Roland

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[range] Can iterator_range also model Random Access Range?
by Mostafa 01 Feb '14

01 Feb '14

It seems that iterator_range can properly model any refinement of the Forward Range concept. Is that right? The reason I ask is that this is not very clear from the documentation, and I had to deduce this from both the iterator_range API and the Random Access Range concept definition. (See documentation at: range/reference/utilities/iterator_range.html) Thanks, Mostafa

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[atomic] Probable documentation issue: how do we know atomic is safe and/or efficient?
by John Maddock 26 Jan '14

26 Jan '14

I'm looking to use Boost.Atomic for the double-checked-locking-idiom, but I'm having trouble discovering a) Whether the library is correctly implemented. b) How efficient (or otherwise) the library is on various platforms. I'm sure the answer to (a) is that it is correct, but I was surprised that atomic<int> relied on the volatile modifier for thread safe load/stores on MSVC, I had assumed that something more than that would have been required, but I know I'm out of date on this stuff! I can't help thinking that questions like this could be allayed by better documentation - specifically what operations are used to ensure correctness on each supported platform, plus rationale and/or link to reference material. My apologies if this has been covered already in the review, and I realize that documentation is a lot of work, but I can see no way to ensure correctness other than through code inspection, so proper documentation is essential in that case. Regards, John.

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C++03 and C++11 ABI compatibility for compiled libraries
by Andrey Semashev 24 Jan '14

24 Jan '14

Hi, I would like to raise the issue of binary compatibility of compiled Boost libraries between C++03 and C++11. I faced this problem with gcc on Linux, but other compilers and platforms may be affected as well. To summarize the problem: * Most, if not all Linux distributions build packages in C++03 mode. This is also the default in gcc. * Some Boost libraries conditionally use C++11 features in their binary interfaces (see [1] as an example). This makes C++03 and C++11 versions of the library binary incompatible. * Given that, users are unable to use C++11 in their code that uses Boost because of linker failures. I don't have the complete list of the offending C++11 features that break ABI, but it would seem that at least scoped enums and rvalue references are among them. Are there any more? I would like to hear opinions on the possible course of action to tackle this problem. Currently, I see 2 choices: 1. Avoid using C++11 features in binary interfaces. This may also mean avoiding STL types in binary interfaces, if they differ between C++03 and C++11 (I didn't verify that). This is my suggested hotfix solution for Boost.Filesystem [1] and the approach I took in Boost.Log. Obviously, this cripples code and error prone, but it keeps a single binary that can be used from any flavor of C++ on the user's side. 2. Compile different versions of Boost libraries, for each supported C++ version. The C++ version should be encoded into the library file names, so that different versions can coexist. This would require changes in Boost.Build and autolinking support code, but I think this would be a better long-term solution. Opinions? [1] https://svn.boost.org/trac/boost/ticket/6779

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Forthcoming Boost.Fiber review
by Nat Goodspeed 20 Jan '14

20 Jan '14

Hi all, The review of Boost.Fiber by Oliver Kowalke is scheduled from Monday, January 6th to January 12th. ----------------------------------------------------- About the library: Boost.Fiber provides a framework for micro-/userland-threads (fibers) scheduled cooperatively. The API contains classes and functions to manage and synchronize fibers similar to Boost.Thread. Each fiber has its own stack. A fiber can save the current execution state, including all registers and CPU flags, the instruction pointer, and the stack pointer and later restore this state. The idea is to have multiple execution paths running on a single thread using a sort of cooperative scheduling (versus threads, which are preemptively scheduled). The running fiber decides explicitly when it should yield to allow another fiber to run (context switching). Boost.Fiberinternally uses coroutines from Boost.Coroutine <http://ok73.funpic.de/boost/libs/coroutine/index.html>; the classes in this library manage, schedule and, when needed, synchronize those coroutines. A context switch between threads usually costs thousands of CPU cycles on x86, compared to a fiber switch with a few hundred cycles. A fiber can only run on a single thread at any point in time. docs: http://ok73.funpic.de/boost/libs/fiber/doc/html/index.html<http://ok73.ok.funpic.de/boost/libs/coroutine/doc/html/> git: https://github.com/olk/boost-fiber src: http://ok73.ok.funpic.de/boost.fiber.zip<http://ok73.ok.funpic.de/boost.coroutine.zip> --------------------------------------------------- Naturally, you need not wait until the review formally opens to start reviewing the Fiber library. Please always state in your review whether you think the library should be accepted as a Boost library! Additionally please consider giving feedback on the following general topics: - 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? Nat Goodspeed Boost.Fiber Review Manager ------------------------------

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GSoC 2014
by Bjorn Reese 20 Jan '14

20 Jan '14

Deadline for registring as a mentoring organization for GSoC 2014 is 14 Feb 2014. Should we start collecting ideas?

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[git] annotated SVN synchronization for boost.test (example only)
by Peter A. Bigot 15 Jan '14

15 Jan '14

Below is an annotated sequence of (bash) command-line git operations that I used in a local copy of Boost.Test to understand what was happening in it, with no intention of proposing this be what the maintainers actually do with the module. Boost.Test is particularly interesting because master has been essentially unchanged for four years, while there are significant modifications pending in develop. A few of the changes on master make the SVN synchronization step tricky. People who want to hone their git-fu might find it workwhile to follow these steps in a local workspace to see how they work. I make no claim that they're the only way the same goal could be reached. I also have not used this for further development, so there the resulting structure may be flawed or contrary to strict git-flow expectations. WARNING: DO NOT paste the entire sequence into a shell window: at a couple of places you must manually do what the comment says (e.g., edit the contents of files to resolve conflicts) in order to reach a successful state. # Revert to a clean state where local branches match the origin, and the # working branches from any previous run of the script have been # removed. git fetch origin git checkout master git reset --hard origin/master git checkout develop git reset --hard origin/develop git branch -D synch/master synch/develop basis # git-merge-base identifies the commit to be used when merging things. # We're looking for something better, so no need to go beyond that one. MERGE_BASE=$(git merge-base develop master) # 635b1e38dd643af264c2ea8f0ba08dfb58337e37 echo ${MERGE_BASE} # Examine the history along master and develop, finding the most recent # SVN revision merged from develop into master. This only works if all # previous SVN revisions were also merged; if only select ones were # merged, it's probably best to skip them and keep looking. For # example, master on Boost.Test merged 81913, 63640, 62426, and a couple # others, but the last version that incorporated most prior fixes was # 57993 merged in ${MST_MP_SHA1}. git log ${MERGE_BASE}..master MST_MP_SHA1=2e4f64197956ccb94b24be4ed32abf25ee4b9dd1 # Now find the develop commit that most recently preceded that one in # SVN history. Basically, this is reviewing the log of differences # for the last commit with a SVN revision less than the one selected in # the previous step. BEWARE: If the revision you picked above doesn't # correspond to a develop branch change (e.g., if you picked 81913 which # didn't go into develop until 82756) you will create pain for yourself. git log ${MERGE_BASE}..develop # Here it's commit 57864 in ${DEV_MP_SHA1} DEV_MP_SHA1=fd8d9b3e4e4ab9656b0d880e8c519eabd134638a # Now take a look at what's different between those versions. That's # what'll get lost in a "-s ours" merge if it subsequently appeared in # develop. git diff ${DEV_MP_SHA1}..${MST_MP_SHA1} # There's some whitespace differences, some casts and error messages, # file permission changes, and two small changes from r81913 that we'll # talk about later. # Here's where my technique differs: You could do an "-s ours" merge # from the selected develop commit into master's HEAD as recommended at # https://svn.boost.org/trac/boost/wiki/StartModMaint#Firstpost-svnconversion… # but if you do you might lose cherry-pick commits on master that are # also on develop. Instead, we'll create a new merge point on master at # the synchronization point, and merge from develop. git checkout -b basis ${MST_MP_SHA1} git merge -s ours -m 'SVN merge basis preserving master' ${DEV_MP_SHA1} # Verify that the differences are the ones we accepted earlier: git diff basis..${DEV_MP_SHA1} # Now, let's do some cleanup, and get master and develop branches that # actually fork at the merge point, rather than simply assume the merge # point is identical. This indirectly helps manage the differences that # we threw away with "-s ours". git checkout -b synch/master master git rebase basis # This should show no differences, because we just inserted a commit # that records parentage but changes no content. git diff master synch/master # Do the same at develop. Here we're going to have to resolve any # conflicts between the selected merge point git checkout -b synch/develop develop git rebase basis # 66 patches in we hit one of the differences: git stat # (MANUAL STEP) There's whitespace at the end of build/Jamfile.v2. Edit # the file to remove the diff markers, stage the changes, and tell # rebase to continue. git add -u git rebase --continue # After 204 patches there's another. git stat # (MANUAL STEP) Here you'll see everything is clean except # include/boost/test/impl/framework.ipp. Search for <<<<<< and edit to # keep the one with the upper-case TUT_SUITE. git add -u git rebase --continue # And we're done. Now let's see what changed: git diff develop synch/develop # Some of the differences between master and develop at the SVN merge # point have gone away; these are the ones I suspect but have not # confirmed would have been lost had we merged to master's HEAD instead # of to the base version. A few changes remain that were in master but # not in develop. # You have a choice at this point. If the repository wasn't already # public, I'd reset master (develop) to synch/master (synch/develop) and # move on. But since they were public, merge them; keeps history, # and makes future actions cleaner. git checkout master git merge -m 'Merge in rebased master' synch/master git checkout develop git merge -m 'Merge in rebased develop' synch/develop # Finally, what would happen if we merged develop into master now? git checkout -b test master git merge develop # Very nearly a clean merge. See what's not staged: git stat -u | grep '^.[^ ]' # ## test # UU include/boost/test/utils/runtime/cla/parameter.hpp # UU include/boost/test/utils/runtime/env/variable.hpp # # Again, open the files and look for the diff markers: one uses m!=0 and # the other !!m. Which is right? Use git-blame: git blame origin/master include/boost/test/utils/runtime/cla/parameter.hpp # The master change came in 954d3ab6 which was SVN commit r81913 by # Vicente J. Botet Escriba. Show the change: git log -p 954d3ab6^! git blame origin/develop include/boost/test/utils/runtime/cla/parameter.hpp # The develop change came in 4f7fc06c which was SVN commit r82756 by # Gennadiy Rozental. Show the change: git log -p 4f7fc06c^! # Note that if, back when selecting the SVN merge point, we'd gone with # r81913 things would be completely bolluxed at this point since the # corresponding change didn't come from the develop branch. # (MANUAL STEP) It's Rozental's project, so pick the develop solution # (!!m). Then stage the changes and commit, editing the message to # indicate how you resolved the conflict. git add -u git commit

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The Community Maintenance Team proposal accepted
by Beman Dawes 14 Jan '14

14 Jan '14

The Steering Committee has voted to accept the Community Maintenance Team proposal, and Marshall Clow has volunteer to act as the team's fearless leader. See https://dl.dropboxusercontent.com/u/9897665/community-maintenance.htmlfor the actual proposal. Thanks to everyone who contributed ideas and discussion. I tried to capture contributors names in the Acknowledgements section of the proposal. Apologies if I missed anyone. --Beman

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Re: [boost] Is there interest in a collection of call stack utilities?
by Aurelian Melinte 14 Jan '14

14 Jan '14

Hello, To follow up on the discussion https://groups.google.com/forum/#!topic/boost-developers-archive/PSwTBEEe0Ao I was not clear if there is interest for it or not. I went ahead and the first cut of the code is now at https://github.com/melintea/Boost-Call_stack Please feel free to take a look and comment. Regards, Aurelian

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