[jira] [Created] (AVRO-3705) avrogencpp needs an option to generate code using std instead of boost

["Andrew Peter Marlow (Jira)" <ji...@apache.org>]

Andrew Peter Marlow created AVRO-3705:
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             Summary: avrogencpp needs an option to generate code using std instead of boost
                 Key: AVRO-3705
                 URL: https://issues.apache.org/jira/browse/AVRO-3705
             Project: Apache Avro
          Issue Type: Improvement
          Components: c++
    Affects Versions: 1.11.0
         Environment: RHEL8. The gcc installed from the Red Hat repo is version 8.5.0 which has an option to use c++17 since that dialect is not the default. The avro-cpp package in the Red Hat repo must have been built with that since it emits code that uses boost.
            Reporter: Andrew Peter Marlow


avrogencpp uses either std or boost in the generated code. It does this depending on how it was built, using #if __cplusplus >= 201703L. If the compiler supports std::any then it used, otherwise boost is used. The assumption is that if the compiler used to build avrogencpp supports C++17 by default then emitted code can use C++17 otherwise the emitted code should use boost. This assumption turns out to have a weakness - if a project uses  a compiler where C++17 is given as an option because it is not the default then the code avrogencpp generates will use boost instead of std.

This problem could be solved if avrogencpp supported a command line option to use c++17. The option could be used by those environments where avrogencpp was built with a version of gcc that does not support c++17 by default but the desire is to use C++17.

This is a serious need because there is a significant difference between boost::any and std::any. The standard any has a small buffer optimisation but boost does not. This means that code generated by avrogencpp that uses boost::any will use heap memory for every case where the generated code uses the any type. This could be avoided if the c++17 was available.



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