Marcel Pfütze created AVRO-2598:
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Summary: C++ standard of library defines C++ standard of libraries
using Avro
Key: AVRO-2598
URL: https://issues.apache.org/jira/browse/AVRO-2598
Project: Apache Avro
Issue Type: Bug
Components: c++
Affects Versions: 1.9.1, 1.9.0
Reporter: Marcel Pfütze
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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