According to C++ Specs, initializer list backwards compatibility:

class-or-identifier ( expression-list(optional) )	(1)
class-or-identifier brace-init-list	(2)	(since C++11)
parameter-pack ...	(3)	(since C++11)

WriterBase::WriterBase(const ValidSchema& schema, size_t syncInterval, std::unique_ptr<OutputStream> streamType, bool resetStr, Codec codec) :
    schema_(schema), encoderPtr_(binaryEncoder()),
    syncInterval_(syncInterval),
    codec_(codec),
    stream_(streamType),
    buffer_(memoryOutputStream()),
    sync_(makeSync()), objectCount_(0), resetStream(resetStr)
{ ... }