January 2019 - Boost - lists.preview.boost.org

Re: [boost] [histogram] discussion of accessor interface design
by Bjorn Reese 28 Jan '19

28 Jan '19

On 1/15/19 12:35 PM, Hans Dembinski via Boost wrote: > Pros: > - really terse > - you can access methods on the pointee with x->method() as well! (useful when histogram counters are not PODs) > - you can iterate over x to get the indices, for (auto i : x) { … } works Doesn't range-for use operator* so you will get the values? > - since x acts like an array to the indices, you can pass it to functions which accept ranges or iterators (it has .begin() and .end()) > - x can be (and is) enhanced with other useful methods > * x.bin(N) returns the current bin interval for the N-th axis, allowing you to access the central value, width, edges > * x.density() returns the current density (bin value divided by product of current bin widths) > Cons: > - *x and x[0] do completely different things: *x gives you the bin value, x[0] gives you the first index An alternative is to rename x[i] to x.index(i).

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UBSan question
by Raffi Enficiaud 25 Jan '19

25 Jan '19

Hi, I am trying to correct for the errors reported by UBSAN in boost.test. A lot of them were false positive, as ... in boost.test, we check the capacity of the framework to catch various errors in the program. I compile/run the tests with the following: ../../../b2 \ --toolset=clang \ cxxflags=-std=c++11 \ cxxflags=-fno-omit-frame-pointer \ cxxflags=-fsanitize=undefined \ cxxflags=-fno-sanitize-recover=undefined \ cxxflags=-fsanitize-recover=integer-divide-by-zero \ cxxflags=-fsanitize-recover=float-divide-by-zero \ linkflags=-fsanitize=undefined \ linkflags=-fno-sanitize-recover=undefined \ linkflags=-fsanitize-recover=integer-divide-by-zero \ linkflags=-fsanitize-recover=float-divide-by-zero \ linkflags=-fuse-ld=gold \ variant=debug I have an exception that is failing the tests on clang-6/ubuntu18.04 (UBSAN exiting the process), but not on gcc-8/ubuntu18.04 (full log below). UndefinedBehaviorSanitizer:DEADLYSIGNAL ==8303==ERROR: UndefinedBehaviorSanitizer: FPE on unknown address This FPE is happening for instance after reading from a null pointer. I've searched on how to silence/blacklist this, but none of the approaches worked so far, and I am not sure what is provoking this FPE. Is there any UBsan specialist? Does anyone have an idea? Thanks, Raffi clang-linux.compile.c++.without-pch ../../../bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/prg_exec_monitor-ts/system-exception-test.o clang-linux.link ../../../bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test testing.capture-output ../../../bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test.run ====== BEGIN OUTPUT ====== prg_exec_monitor-ts/system-exception-test.cpp:38:15: runtime error: division by zero #0 0x42d03f (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x42d03f) #1 0x42f344 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x42f344) #2 0x42e8b1 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x42e8b1) #3 0x43dafa (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x43dafa) #4 0x43a6f2 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x43a6f2) #5 0x436d13 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x436d13) #6 0x43726f (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x43726f) #7 0x42d148 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x42d148) #8 0x42e216 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x42e216) #9 0x7f648e20fb96 (/lib/x86_64-linux-gnu/libc.so.6+0x21b96) #10 0x405859 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x405859) UndefinedBehaviorSanitizer:DEADLYSIGNAL ==8303==ERROR: UndefinedBehaviorSanitizer: FPE on unknown address 0x00000042d049 (pc 0x00000042d049 bp 0x7ffe501ec660 sp 0x7ffe501ec630 T8303) #0 0x42d048 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x42d048) #1 0x42f344 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x42f344) #2 0x42e8b1 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x42e8b1) #3 0x43dafa (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x43dafa) #4 0x43a6f2 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x43a6f2) #5 0x436d13 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x436d13) #6 0x43726f (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x43726f) #7 0x42d148 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x42d148) #8 0x42e216 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x42e216) #9 0x7f648e20fb96 (/lib/x86_64-linux-gnu/libc.so.6+0x21b96) #10 0x405859 (/home/bambooagent/bamboo-agent-home/xml-data/build-dir/RS-BCB187-CLAN/library/bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test+0x405859) UndefinedBehaviorSanitizer can not provide additional info. ==8303==ABORTING EXIT STATUS: 1 ====== END OUTPUT ====== (failed-as-expected) ../../../bin.v2/libs/test/test/system-exception-test.test/clang-linux-6.0.0/debug/threading-multi/visibility-hidden/system-exception-test.run

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Any interest in Compile Time Hash Containers library?
by Ivan Matek 25 Jan '19

25 Jan '19

Hi everybody, my first message, I hope I do not mess this up. I was contemplating writing a Compile Time Hash Containers library and I wrote a test implementation for sets and benchmarked it against mostly ska:: sets since they are the best. Document is here: https://docs.google.com/document/d/1IsUiWl3K0h2pgttYgMt67CxgJ3zeXBKZEA7hvAQ… It is quite long, but it aims to provide a introduction to the problem for people unfamiliar with details of hashing, and also it goes into a lot of discussions, if you care just about the numbers you can skip the "boring parts". My interpretation of benchmarks is that it performs very well in some cases, decently in others, but I am biased. :) Code is not available online since I do not want to dump a test project online without extensive documentation, but if somebody has a problem that may be benefited by this test implementation feel free to let me know, I would be happy to get some real world feedback on prototype. Limitations is that test implementation only works for sets, so no maps and if your objects are not integers you will probably not get much speedup. Also if your set has more than 100ish items GCC will run out of memory and VC++ does not compile code at all, so clang is the only way for most use cases today. One more disclaimer is that I do not want this library to be some beast like ranges that takes years to implement, so if after reading the document you consider implementation quite basic I won't be offended :) In other words I feel that library like this although relatively simple compared to regular Boost libraries can provide quite a lot of benefit for some usecases where people really really care about performance of hash containers where values are known during compile time. I know you can not predict the future of an unimplemented library, but I would be happy with some general feedback, and if you think this library would be nice boost proposal I would be interested in some pointers wrt how to proceed. If somebody wonders how user code looks at the moment: #include "cxhash_set.h" // also could be a result of constexpr function, no need for initializer list static constexpr std::array<int, 20> ints{0,1,2,3,5,8,21,34,64,128,256,512,1024,1701,1729,2048,4096,12345,123456,1234567}; int main() { cxhash_set<ints> ints_set; // contains could(should be?) static, but for now it is "normal" member fn std::cout << std::boolalpha << ints_set.contains(21) << std::endl; std::cout << std::boolalpha << ints_set.contains(22) << std::endl; } P.S. feel free to comment in the google doc, I actually find mailing lists quite limited when it comes to prolonged and or detailed discussions. Maybe we can ping Alexandrescu for an instance of dlang forums, so we get a better discussion tools, and he gets a way to convert us to D. :)

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Status of Boost GSoC 2019?
by Mateusz Loskot 24 Jan '19

24 Jan '19

Hi, (I've asked this David Bellot by email some time ago. No response arrived, so asking here again.) One student asked about GSoC recently [1] but w/o answer. An empty repo for this year has been created. And, the timeline [3] says organizations need to apply by Feb 6. I wonder, what is the status of the preparation for GSoC 2019? [1] https://lists.boost.org/Archives/boost/2019/01/244849.php [2] https://github.com/BoostGSoC19 [3] https://summerofcode.withgoogle.com/how-it-works/ Best regards, -- Mateusz Loskot, http://mateusz.loskot.net <http://mateusz.loskot.net>

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[stacktrace] libbacktrace callback for backtrace_pcinfo invalid return value
by Muazin Mugadr 24 Jan '19

24 Jan '19

Hello all See also: https://stackoverflow.com/questions/54333608/boost-stacktrace-not-demanglin… I am cross compiling boost on Unix for Windows with MINGW. I am using libbacktrace compiled using the same toolchain from here: https://github.com/ianlancetaylor/libbacktrace Digging through the code of libbacktrace I was able to deduce that in a success case the return value of backtrace_pcinfo will be the return value of the callback supplied to that function (for DWARF search). The callback boost is giving looks like this: inline int libbacktrace_full_callback(void *data, uintptr_t /*pc*/, const char *filename, int lineno, const char *function) { pc_data& d = *static_cast<pc_data*>(data); if (d.filename && filename) { *d.filename = filename; } if (d.function && function) { *d.function = function; } d.line = lineno; return 0; } As you can see it will always return 0. This causes an issue with the way the function is called: ::backtrace_pcinfo:( state, reinterpret_cast<uintptr_t>(addr), boost::stacktrace::detail::libbacktrace_full_callback, boost::stacktrace::detail::libbacktrace_error_callback, &data ) || ::backtrace_syminfo:( state, reinterpret_cast<uintptr_t>(addr), boost::stacktrace::detail::libbacktrace_syminfo_callback, boost::stacktrace::detail::libbacktrace_error_callback, &data ); If the symbol is found using backtrace_pcinfo the return value will be 0. If its not found it will be 0. It will always use the value provided by backtrace_syminfo. Is this intended? BR Cromon

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Tests: Runtime type_mismatch after upgrade to 1.69
by Florian Lindner 24 Jan '19

24 Jan '19

Hello, after my distribution rolled out the upgrade to Boost 1.69 I am unable to compile my application anymore. I try to get the log_level set. Minimal compiling example: #define BOOST_TEST_DYN_LINK #include <boost/test/unit_test.hpp> #include <boost/test/unit_test_parameters.hpp> bool init_unit_test() { using namespace boost::unit_test; auto logLevel = runtime_config::get<log_level>(runtime_config::btrt_log_level); return true; } int main(int argc, char* argv[]) { int retCode = boost::unit_test::unit_test_main( &init_unit_test, argc, argv ); return retCode; } which compiles fine g++ -std=c++11 -lboost_unit_test_framework boosttesting.cpp but gives an runtime error: % ./a.out Test setup error: boost::runtime::arg_type_mismatch: Access with invalid type for argument corresponding to parameter log_level Thanks! Florian

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C++Now 2019 Registration is Open
by Jon Kalb 24 Jan '19

24 Jan '19

Boosters, Registration for C++Nows 2019 (aka BoostCon) is now open: http://cppnow.org/announcements/2019/01/2019-registration-is-open/ Please help us to spread the word about this announcement. Thanks. Note that the Aspen Meadows Resort online registration link is also up on the lodging page. Because there will be another group in the hotel, we’ve been allocated fewer rooms this year. Please either reserve a room very soon or plan to stay at the Lamplighter or another hotel in town. See you in Aspen in May. Jon

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[gsoc19][GIL] Project proposal
by Miral Shah 23 Jan '19

23 Jan '19

Hello everyone, I am Miral Shah a computer engineering student from India. I have been talking with Boost.GIL community on GIL's Gitter channel since last few weeks to come up with the new idea for GSoC19. After many suggestions and a long discussion on various ideas with the contributors, we have come up with the idea to expand the GIL by introducing new image processing algorithms into it. I would also like to thank Stefan Seefeld and Mateusz Loskot for their guidance and support. Proposal idea can be found here: https://github.com/boostorg/gil/wiki/GSoC-2019 Thank you, Miral Shah

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Boost log issues and workarounds
by hh h 21 Jan '19

21 Jan '19

Hi, I like the boost log, but there are many small issues, appreciate your kind help: I followed the following link to use a good macro LOG: https://stackoverflow.com/questions/35895199/boost-log-and-severity-local-a… But calling LOG(error) caused much trouble for the name space collision, alternative is to use full namespace boost::log::trivial::error, but that is too cumbersome,I tried to use an uppercase ERROR to replace it in an enum ERROR = boost::log::trivial::error, obviously that could not be complied, although it is defined as enum severity_level in trivial.hpp, it does not look like the boost::log::trivial::error is an enum value. Any workarounds? Another issue from that link is it has to call LOGGABLE prior to call LOG(error) in each function, that makes more clumsy, software developers in my team are not happy about it. Any workaround to have a fixed argument in BOOST_LOG_STREAM_WITH_PARAMS, without need to claim boost::log::sources::severity_logger<boost::log::trivial::severity_level> slg; in each function? You guys are genius that must be a way to do it, appreciate your advice. Thank you

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[lockfree] wait-free multi-queue?
by Shawn Yarbrough 18 Jan '19

18 Jan '19

Is it practical to have a wait-free, multi-producer/multi-consumer queue? I ask because Boost's Lockfree multi-queue is only advertised as being "lock-free". (Boost does offer a wait-free single-queue.) https://www.boost.org/doc/libs/1_69_0/doc/html/lockfree.html Shawn Y.

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