in code/include/swoc/BufferWriter.h [498:502]
inline FixedBufferWriter::FixedBufferWriter(char *buffer, size_t capacity) : _buffer(buffer), _capacity(capacity) {
if (_capacity != 0 && buffer == nullptr) {
throw(std::invalid_argument{"FixedBufferWriter created with null buffer and non-zero size."});
};
}