Let's assume that the bug is in libxml2, should postgres crash or should it have some kind of protection against it?
Yeah. The segfault is inside xmlParserPrintFileContext(), so really there is at least one libxml2 bug here and possibly two. Maybe it should have been able to cope with such large input, or maybe not, but for sure its printing functions should have been able to cope with the state at the time the error was reported.
I don't think there's much we can do about it; you need to report this to the libxml2 folk.
