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Introduces Printer::Shrink, to let the user avoid an assert if its output stream will disappear before our destructor.
The idea here is that if you do this:
Then depending on your compiler, it may decide to call the move operator of std::string on that return statement. At that point,
output
is becoming empty, and its size becomes zero. Meaning that this assert here will fire, during the actual destruction ofprinter
:https://github.com/google/protobuf/blob/master/src/google/protobuf/io/zero_copy_stream_impl_lite.cc#L190
This is currently causing this issue on grpc: grpc/grpc#1769.
I would also argue that the right thing to do would be to avoid calling
Shrink
altogether in the destructor ofPrinter
, and let the user do that manually, but I didn't want to change actual code behavior at that point.