What could cause a stream to enter the “bad” state?

Question

In C++, each stream has a bad bit:

This flag is set by operations performed on the stream when an error occurs while read or writing data

Answer 1

According to cppreference.com :

The standard library sets badbit in the following situations:

• Insertion into the output stream by put() or write() fails for any reason.

• Insertion into the output stream by operator<<, std::put_money or std::put_time, could not complete because the end of the output stream was reached (The facet's formatting output function such as num_put::put() or money_put::put(), returns an iterator iter such that iter.failed()==true)

• Stream is constructed with a null pointer for rdbuf(), or putback()/unget() is called on a stream with a null rdbuf(), or a null pointer passed to operator<<(basic_streambuf*)

• rdbuf()->sputbackc() or rdbuf()->sungetc() return traits::eof() to putback() orunget()`

• rdbuf()->pubsync() returns -1 to sync(), to flush(), or to the destructor of ostream::sentry on a unitbuf stream

• Exception is thrown during an I/O operation by any member function of the associated stream buffer (e.g. sbumpc(), xsputn(), sgetc(), overflow(), etc)

• Exception is thrown in iword() or pword() (e.g. std::bad_alloc)

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