November 2022 - Boost-users

[release] Boost 1.81.0 beta 1 released
by Marshall Clow 17 Nov '22

17 Nov '22

Boost release 1.81.0 beta 1 is now available at: https://boostorg.jfrog.io/artifactory/main/beta/1.81.0.beta1/source/ The SHA256 checksums are: 135f03965b50d05baae45f49e4b7f2f3c545ff956b4500342f8fb328b8207a90 boost_1_81_0_b1.tar.gz 736b041748d04c573d145613161cf2e54beb210c5511b67e6fac5510b82b6646 boost_1_81_0_b1.7z 941c568e7ac79aa448ac28c98a5ec391fd1317170953c487bcf977c6ee6061ce boost_1_81_0_b1.tar.bz2 c58d50acf58a98d4f5a7d891257d154efa50ca90312ca446586c7b4f9b7d3f14 boost_1_81_0_b1.zip Release notes (still need updates): https://www.boost.org/users/history/version_1_81_0.html Please try the beta and report any problems you encounter. Thanks to everyone who contributed to the release. -- Boost Release Team

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Partial serialization of a program
by Markus Lavin 06 Nov '22

06 Nov '22

I have a simulator type program where I want to be able to save (and load) the current simulation state using Boost serialization. The program, as with most programs, consists of a part that is static during run-time and a part that is dynamic. Ideally I would like to serialize only the dynamic part but this however raises the following problem. If a serialized object in the dynamic part contains a pointer to a non-seralized object in the static part then how do I deal with that. Clearly the address cannot be serialized since it may change between builds and even between runs (ASLR). The program does contain a 'registry' though where all relevant static objects are registered with a unique identifier. So question is would it somehow be possible to have Boost serialization use this registry to serialize the unique identifier instead of trying to serialize the entire object when one of those pointers are serialized? As far as I can tell the documentation does not mention this situation and extensive web searching yields very little as well. Any advice appreciated! -Markus

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Question about boost::multi_index emplace operations
by Pavel Vazharov 03 Nov '22

03 Nov '22

Hi there, Is there a way to emplace (key, value) in boost multi_index hashed index in such a way that the value is not moved/stolen if the key is already present? As far as I checked the implementation for emplace (and emplace_) the node is eagerly created and the key and the value are moved into the node and then the insertion operation takes place. If the insertion fails the node is destroyed but the outside value is lost/stolen in all cases. What I actually need is to create the value only if the key is not present, because the creation is expensive, and I'd like to avoid the find+emplace or insert empty value + modify call. (As far as I checked, the value can't be modified directly from the returned iterator because it's const and will need const_cast to work). I thought to use emplace with some machinery for lazy creation struct creator { operator value_type () { return ...; } // create the value lazily, on demand }; The creator is passed to emplace instead of the actual value. However, this doesn't help because the node is eagerly created and the above operator is always called. Thanks, Pavel.

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