November 2020 - Boost-users - lists.stage.boost.cppalliance.org

Clarification on statechart post_event vs process_event within react()
by John McCabe 10 Jan '22

10 Jan '22

Hi, Apologies if this has already been answered/clarified, but my search of the internet to try to get a definitive answer, at least one I recognised as being definitive, was unsuccessful. Below I have posted some source code, based on the stopwatch example from the tutorial, but using an 'external' object to delegate the actual handling of event stuff to and using the state, rather than simple_state base class, and some other tweaks. This is a cut down version of something that someone I work with has devised, but I just wanted to get a clear answer on whether process_event() should be getting called in cases like this. I think it probably should not since, in the code below, you change state (with a state object's destructor being executed) whilst you're executing that state's react(EvStartStop) function. If someone can confirm this is the correct interpretation that would be very much appreciated. Any questions, feel free to ask (BTW - I'm compiling for C++17) John PS - In case it's of any use, the output from running this code is: ------ Entered Active Entered Stopped Stopped - payload2 m_charValue: a Exited ~Stopped <<<--- This is the bit I don't like the look of because... Entered Running Active - payload2 m_charValue: a <<<--- ... this happens from the forward_event() call payload1 value1: 20 payload1 value2: 200.2 Exited ~Running Entered Stopped Exiting Program Exited ~Stopped Exited ~Active ------ If I swap the //*** comments to the doProcess() lines instead of doPost(), the output seems more sensible ------ Entered Active Entered Stopped Stopped - payload2 m_charValue: a Exited ~Stopped Entered Running Active - payload2 m_charValue: a payload1 value1: 20 payload1 value2: 200.2 Exited ~Running Entered Stopped Exiting Program Exited ~Stopped Exited ~Active ------ ========== code =========== #include <boost/statechart/event.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/state.hpp> #include <boost/statechart/transition.hpp> #include <boost/statechart/custom_reaction.hpp> #include <boost/mpl/list.hpp> #include <iostream> #include <string> namespace sc = boost::statechart; namespace mpl = boost::mpl; // Forward declare a handler 'class' that's going to have activity delegated to it struct Handler; // Normal example start/stop and reset events struct EvStartStop : sc::event<EvStartStop> {}; struct EvReset : sc::event<EvReset> {}; // A couple of events that carry data with them struct EvPayload1 : sc::event<EvPayload1> { EvPayload1(int value1, double value2) : m_value1 { value1 }, m_value2 { value2 } {}; int m_value1 { 0 }; double m_value2 { 0.0 }; }; struct EvPayload2 : sc::event<EvPayload2> { EvPayload2(const char& charValue) : m_charValue { charValue } {}; char m_charValue { false }; }; // Back to the example bits struct Active; struct StopWatch : sc::state_machine<StopWatch, Active> { typedef sc::transition<EvReset, Active> reactions; // The extra 'handler' stuff void setHandler(Handler* handler) { m_handler = handler; }; Handler* getHandler() const { return m_handler; }; Handler* m_handler { nullptr }; // Used to make post_event() accessible from an external class...seems unpleasant, but... using sc::state_machine<StopWatch, Active>::post_event; }; // The implementation of the Handler class; created with a reference to a StopWatch object struct Handler { Handler(StopWatch& stopWatch) : m_stopWatch { stopWatch } {}; void doPost() { m_stopWatch.post_event(EvStartStop()); } void doProcess() { m_stopWatch.process_event(EvStartStop()); } StopWatch& m_stopWatch; }; struct Stopped; struct Active : sc::state<Active, StopWatch, Stopped> { Active(my_context ctx) : my_base { ctx } { std::cout << "Entered Active" << std::endl; }; ~Active() { std::cout << "Exited ~Active" << std::endl; }; typedef mpl::list<sc::custom_reaction<EvPayload1>, sc::custom_reaction<EvPayload2>, sc::transition<EvReset, Active>> reactions; sc::result react(const EvPayload1& payload1) { std::cout << "payload1 Event NOT HANDLED" << std::endl; return discard_event(); } sc::result react(const EvPayload2& payload2) { std::cout << "Active - payload2 m_charValue: " << payload2.m_charValue << std::endl; return discard_event(); } }; struct Running : sc::state<Running, Active> { Running(my_context ctx) : my_base { ctx } { std::cout << "Entered Running" << std::endl; }; ~Running() { std::cout << "Exited ~Running" << std::endl; }; typedef mpl::list<sc::custom_reaction<EvPayload1>, sc::transition<EvStartStop, Stopped>> reactions; sc::result react(const EvPayload1& payload1) { std::cout << "payload1 value1: " << payload1.m_value1 << std::endl; std::cout << "payload1 value2: " << payload1.m_value2 << std::endl; //***context<StopWatch>().getHandler()->doPost(); context<StopWatch>().getHandler()->doProcess(); return discard_event(); } }; struct Stopped : sc::state<Stopped, Active> { Stopped(my_context ctx) : my_base { ctx } { std::cout << "Entered Stopped" << std::endl; }; ~Stopped() { std::cout << "Exited ~Stopped" << std::endl; }; typedef mpl::list<sc::custom_reaction<EvPayload2>, sc::transition<EvStartStop, Running>> reactions; sc::result react(const EvPayload2& payload2) { std::cout << "Stopped - payload2 m_charValue: " << payload2.m_charValue << std::endl; //***context<StopWatch>().getHandler()->doPost(); context<StopWatch>().getHandler()->doProcess(); return forward_event(); } }; int main() { StopWatch myWatch; Handler myHandler(myWatch); myWatch.setHandler(&myHandler); myWatch.initiate(); myWatch.process_event(EvPayload2 { 'a' }); myWatch.process_event(EvPayload1 { 20, 200.2 }); std::cout << "Exiting Program" << std::endl; return 0; }

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[Beast] Slow HTTP connect on Windows. Normal?
by Dominique Devienne 14 Dec '20

14 Dec '20

Hi. I'm writing a small interaction between: 1) a Boost.Beast-based HTTP server (based on http_server_async.cpp example) 2) a Boost.Beast-based HTTP client (based on http_client_sync.cpp example) When I log the time it takes to resolve the server address and connect to it, then issue my HTTP request, it takes over 1 second (Win10, VS2019, C++17, Release, localhost for both client and server): 2020-11-25T09:46:37.473936 Prologue in 0.001s 2020-11-25T09:46:37.482470 Resolved in 0.008s 2020-11-25T09:46:38.506180 Connected in 1.023s 2020-11-25T09:46:38.509607 OK: Authenticated; in 0.003s While the same on Linux (RH7.5) is just over 2ms: 2020-11-25T09:45:45.515926 Prologue in 0.000s 2020-11-25T09:45:45.517083 Resolved in 0.001s 2020-11-25T09:45:45.517550 Connected in 0.000s 2020-11-25T09:45:45.518010 OK: Authenticated; in 0.000s That's a huge difference! Almost 500x... And when I contact the same HTTP server on Windows, but from Chrome this time, it takes about 300ms, and if I hit reload rapidly, the time jumps around to as low as 3ms, and as high as 300ms (the same initial delay), with ~50ms and ~100ms in between. (I also see several different connections being established, for some reason...) I've seen similar differences between Windows and Linux connection times, but with WebSocketPP-based client and server this time, also based on Boost.ASIO. Q1: Am I doing anything wrong? I.e. is this "normal" somehow? Q2: How come Chrome, on Windows too, is 3x faster than ASIO-based clients, with the same Beast-based server? Given the high connect time on Windows, I thought I'd try to keep the connection open on the client, and issue several send-request/read-response pairs, using the Beast-based (sync) HTTP client, but only the first one works correctly, the 2nd errors out with: Error: An established connection was aborted by the software in your host machine I suspect it is a user-error, with the server closing the connection, despite the Keep-Alive HTTP header being present server-side on the request. Q3: Given the Beast HTTP examples I'm based off, would anyone have suggestions on what changes are necessary to allow the client issuing several (non-overlapping) requests to the server, on the same connection? (since connecting is so expensive). Q4: And for better performance, what about overlapping request/response pairs, with HTTP pipelining. How to set that up on the client and server with Beast? Thanks for any help on this. --DD PS: Great examples in Boost.Beast BTW. Thanks Vinnie.

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Boost.Numeric.Interval: Please specify rounding control mechanism
by Bastien Commelongue 01 Dec '20

01 Dec '20

Hello, I am building an app for IOS (ARM) and I had this issue while compiling: *Boost.Numeric.Interval: Please specify rounding control mechanism.* C99 version should be used in this case but __USE_ISOC99 is not defined. Modifying the condition with this code (using __cplusplus) fixed the issue: *boost/numeric/interval/hw_rounding.hpp(36)* *#if defined(BOOST_NUMERIC_INTERVAL_NO_HARDWARE) && (defined(__USE_ISOC99) || defined(__MSL__) || (defined __cplusplus && __cplusplus >= 201103L))# include <boost/numeric/interval/detail/c99_rounding_control.hpp>#endif* Let me know if I missed something or if you plan to integrate this modification in a next version. Cheers, Bastien Commelongue

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PolyCollection
by Brian Wood 30 Nov '20

30 Nov '20

Shalom Hey, is anyone using PolyCollection? I have serialization support for it: https://github.com/Ebenezer-group/onwards/tree/master/example/poly If you considered it, but chose an alternative library, what was the reason? Thanks. Brian Ebenezer Enterprises - Enjoying programming again. https://webEbenezer.net

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Re: [Boost-users] [multi_array] Feature request: constructor and resize from values
by DV Henkel-Wallace 30 Nov '20

30 Nov '20

If an object does not have a default constructor what could it mean to have a block of memory holding one that has not been initialized? How would your program know if the object had been properly initialized or not? There are three ways to address this: 1 - A pointer, as already mentioned. A null pointer means the spot does not refer to ("contain") a valid object -- or any object at all. 2 - use a variant 3 - create a default constructor (which you could do by changing the signature of your constructor to something like (int = 0) or (int = -1) assuming those values are invalid). In all cases, regardless of semantics or implementation you'll either have to check at runtime for a valid object OR, if you know for other reasons which locations are valid, use the default constructor with any value you'd like. If you don't want to use pointers there are a couple of other possibilities: > > Date: Sun, 22 Nov 2020 12:06:04 +0100 > From: Eugenio Bargiacchi <svalorzen(a)gmail.com <mailto:svalorzen@gmail.com>> > > Ah, sorry, I thought it would have been automatically clear. Consider this > example: > > class A { > public: > A(int) {} > }; > > boost::multi_array<A,2> array(boost::extents[2][2]); // Compiler error > boost::multi_array<A,2> array(boost::extents[2][2], A(3)); // What I would > like > > array.resize(boost::extents[2][2]); // Again, compiler error > array.resize(boost::extents[2][2], A(2)); // What I would like > > The variable `array` cannot be constructed in any way, as multi_array will > try to default-construct it, and that will fail. Trying to simply create > `array` with its default constructor works (although it will obviously be a > zero-sized array), but when trying to resize it (to actually store things), > the same thing will happen.

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[multi_array] Feature request: constructor and resize from values
by Eugenio Bargiacchi 22 Nov '20

22 Nov '20

I'd love to be able to use multi_array with classes that do not have a default constructor. At the moment, this is impossible, as both the constructor and resize functions only take extents as arguments (and possibly some other options), but no value_type, as for example std::vector does. Thus, trying to store objects without a default constructor in a multi_array results in hard compiler errors, with no workaround that I know of. This happens to me fairly often, as I use multi_array to organize sets of complex objects. If there is a technical reason why this is not possible, I would also be happy to learn it. Best regards, Eugenio Bargiacchi

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[xpressive] I got a crash in after i upgrade from 1.44 to 1.74
by forston_shi＠trendmicro.com 20 Nov '20

20 Nov '20

Hi Boost Users I met a crash in following code after I upgrade from 1.44 to 1.74, When I used "-O1 -DNDEBUG" to compile, it will crash. But when I used "-O1" or "-DNDEBUG" or "-O0 -DNDEBUG", it will not crash. In 1.44, all of them are ok. My GCC version is 4.1.2 and test in redhat-AS 4 32 bit. callstack #0 at ./boost_1_74_0_bk/boost/xpressive/detail/static/transmogrify.hpp:160 160 char const *name_end = m.name_ + std::strlen(m.name_); #1 at ./boost_1_74_0_bk/boost/proto/transform/detail/preprocessed/fold_impl.hpp:80 #2 at ./boost_1_74_0_bk/boost/proto/transform/detail/preprocessed/fold_impl.hpp:80 #3 at ./boost_1_74_0_bk/boost/xpressive/detail/static/compile.hpp:79 #4 at ./boost_1_74_0_bk/boost/xpressive/detail/static/compile.hpp:99 #5 0x08049d5f in main () at ./boost_1_74_0_bk/boost/xpressive/basic_regex.hpp:252 Can you help to check this problem? Best regards Forston callstack Following is source code. #include <boost/xpressive/basic_regex.hpp> #include <boost/xpressive/regex_primitives.hpp> #include <boost/xpressive/match_results.hpp> #include <boost/xpressive/regex_algorithms.hpp> int main(int argc, char* argv[]) { std::wstring uri_string = L"https://192.168.1.1/test"; printf("begin regex_match %ls \n ", uri_string.c_str()); using namespace boost::xpressive; static wsregex const uri_regex = bos >> (s1 = (alpha >> *(alnum | L'+' | L'-' | L'.'))) >> L"://" >> (s2 = *(alnum | L'-' | L'.' | L':' | L'@' | L'[' | L']' | L'_')) >> !(as_xpr(L'/') >> (s3 = (*_))) >> eos ; wsmatch result; try { if (!regex_match(uri_string, result, uri_regex)) { printf( "regex_match failed %ls \n ", uri_string.c_str()); return -1; } } catch (std::exception& e) { printf("regex_match failed %ls \n ", uri_string.c_str()); return -1; } printf("end regex_match success %ls \n ", uri_string.c_str()); return 0; } TREND MICRO EMAIL NOTICE The information contained in this email and any attachments is confidential and may be subject to copyright or other intellectual property protection. If you are not the intended recipient, you are not authorized to use or disclose this information, and we request that you notify us by reply mail or telephone and delete the original message from your mail system. For details about what personal information we collect and why, please see our Privacy Notice on our website at: Read privacy policy<http://www.trendmicro.com/privacy>

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[asio] Prevent socket inheritance on Windows
by Klebsch, Mario 17 Nov '20

17 Nov '20

Hello everybody, I am using boost as communication framework in a library for Windows. I am getting problems, when the client code, that uses our library, creates windows processes and inherits handles, e.g. by using popen(). I currently observing two problems. 1. Even though my library has closed the socket, the peer keeps an active connection. 2. When there is a pending async read operation, calling close() does not lead to the read handler being invoked with an error. My library closes a socket in its shutdown process and because it also terminates the io_service during shutdown, it waits for the termination of the pending read operation. The second problem is the one, that is visible to the client, since our library hands during shutdown. Unfortunately it is not triggered by just inheriting a socket handle to a child process. I know, the socket handle gets inherited to the child process and when I kill the child process, the pending async operation terminates. I also have seen the pending read operation to terminate, then the peer system sends some data. The data seems to be read fine, although the socket has already been closed by our library. The io_service is blocked in the call to GetQueuedCompletionStatus() on its io completion port. It seems, the io completion port still is linked the the socket, although the socket has been closed. The problem is triggered reliably, when using my fully integrated library, but I have not yet managed to write a small simple sand alone program to demonstrate this problem. * Does anybody on this mailing list has a clue, what may cause the 2nd problem, where the async operation does not terminate upon closing the socket. * Does anybody know of a reliable way to prevent an asio socket from being inherited. I found some web pages mentioning WSA_FLAG_NO_HANDLE_INHERIT, but have not found a way to get boots to use this flag other than patching my boost source code. Thanks to everybody, Mario -- Mario Klebsch Actia I+ME GmbH Mario.klebsch(a)ime-actia.de<mailto:Mario.klebsch@ime-actia.de> Dresdenstrasse 17/18 Fon: +49 531 38 701 716 38124 Braunschweig Fax: +49 531 38 701 88 Germany

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[release] Boost 1.74.0 beta 1 released
by Marshall Clow 14 Nov '20

14 Nov '20

Boost release 1.75.0 beta 1 is now available at: <https://dl.bintray.com/boostorg/beta/1.75.0.beta1/source/> The SHA256 checksums are as follows: 3f01d3e5dc822e151892040d4667e364ea808d208d2e49cc7a1802bd4da3d4cc boost_1_75_0_b1.7z 9b75a80f845d4ae312e3c9151ffdfe3fed450973095e0a15c68d0be394f2f2df boost_1_75_0_b1.tar.bz2 123519d4b056fbbd69e452db880abe2c7e55f21779d44a4d6b6c714d5c13c3ee boost_1_75_0_b1.tar.gz b73e01d22d5b3d2ff82f14a371e3974fab30448bf6ff5ac8b9c829539a19c2d7 boost_1_75_0_b1.zip For details of what's in the release, see <https://www.boost.org/users/history/version_1_75_0.html>. Please download the beta, give it a try, and report any problems you encounter. Thanks, -- The Boost Release Team

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[release] Boost 1.75.0 Beta 1 Release Candidate 2
by Marshall Clow 13 Nov '20

13 Nov '20

The second release candidates for the 1.75.0 beta release are now available at: <https://dl.bintray.com/boostorg/beta/1.75.0.beta1/source/> The SHA256 checksums are as follows: 3f01d3e5dc822e151892040d4667e364ea808d208d2e49cc7a1802bd4da3d4cc boost_1_75_0_b1_rc2.7z 9b75a80f845d4ae312e3c9151ffdfe3fed450973095e0a15c68d0be394f2f2df boost_1_75_0_b1_rc2.tar.bz2 123519d4b056fbbd69e452db880abe2c7e55f21779d44a4d6b6c714d5c13c3ee boost_1_75_0_b1_rc2.tar.gz b73e01d22d5b3d2ff82f14a371e3974fab30448bf6ff5ac8b9c829539a19c2d7 boost_1_75_0_b1_rc2.zip As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. -- The Release managers

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