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Posted to dev@avro.apache.org by "Marcel Pfütze (Jira)" <ji...@apache.org> on 2019/10/16 14:33:00 UTC
[jira] [Updated] (AVRO-2598) C++ standard of library defines C++
standard of projects using Avro
[ https://issues.apache.org/jira/browse/AVRO-2598?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Marcel Pfütze updated AVRO-2598:
--------------------------------
Summary: C++ standard of library defines C++ standard of projects using Avro (was: C++ standard of library defines C++ standard of libraries using Avro)
> C++ standard of library defines C++ standard of projects using Avro
> -------------------------------------------------------------------
>
> Key: AVRO-2598
> URL: https://issues.apache.org/jira/browse/AVRO-2598
> Project: Apache Avro
> Issue Type: Bug
> Components: c++
> Affects Versions: 1.9.0, 1.9.1
> Reporter: Marcel Pfütze
> Priority: Major
>
> SInce Avro 1.9.0 there is an if macro in a lot of headers that uses the current C++ standard.
> If you build the library from source and use it in another project this can lead to segfaults.
> Example of macro:
> {code:c++}
> template<typename T> T& GenericDatum::value() {
> return (type_ == AVRO_UNION) ?
> #if __cplusplus >= 201703L
> std::any_cast<GenericUnion>(&value_)->datum().value<T>() :
> *std::any_cast<T>(&value_);
> #else
> boost::any_cast<GenericUnion>(&value_)->datum().value<T>() :
> *boost::any_cast<T>(&value_);
> #endif
> {code}
> In our case we build the library from source (which uses the c++11 by default) and used it in a project using C++17. There's very little indication to the user why this happens.
> My proposals:
> * Move implementation from header to source file so that the used standard is decided at build time.
> * Use the [CMAKE_CXX_STANDARD |https://cmake.org/cmake/help/v3.1/variable/CMAKE_CXX_STANDARD.html] functionality provided by cmake to set the standard. In this way the standard can also easily set when building the code without actually manipulating the CMakeLists.txt file. Of course the --std=c++11 [here|https://github.com/apache/avro/blob/89218262cde62e98fcb3778b86cd3f03056c54f3/lang/c%2B%2B/CMakeLists.txt#L55] can be removed.
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