N != numeric_limits::max() (18.3.2) and n characters have been extracted so farĮnd-of-file occurs on the input sequence (in which case the function calls setstate(eofbit), which may throw ios_base::failure (27.5.5.4)) Characters are extracted until any of the following occurs: After constructing a sentry object, extracts characters and discards them. WhenĮffects: Behaves as an unformatted input function (as described above). The problem here is the same basic issue as the problem you linked just a different manifestation.
Istream ignore code#
Well, bad news, you're right, the code is blocking at step 2 inĬharacter to be entered (really, checking if it's EOF after those two characters), and by the spec, this is apparently the correct thing to do, I think? You try to discard exactly two characters withīut in fact things seem to stop at step 2 until you give it more input, and the underscores only appear later. How can I make it so that the message gets printed immediately after the two characters are discarded and thenĪfter a lot of back and forth in the comments (and reproducing the problem myself), it's clear the problem is that: Inputting something like 'b' and hitting Enter immediately after the first input (so 2 after the characters get discarded, 'p' and '\n') keeps 'b' in the buffer and immediately passes it to cin, without first printing the message. This test is disabled if delim is Traits::eof()Īfter I've given it more than 2 characters to discard. The delimiter character is extracted and discarded. The next available character c in the input sequence is delim, as determined by Traits::eq_int_type(Traits::to_int_type(c), delim). This test is disabled in the special case when count equals std::numeric_limitsstd::streamsize::max()Įnd of file conditions occurs in the input sequence, in which case the function calls setstate(eofbit)
After constructing and checking the sentry object, it extracts characters from the stream and discards them until any one of the following conditions occurs:Ĭount characters were extracted. Ignore behaves as an UnformattedInputFunction. However, let's say I've got the following program:Įxtracts and discards characters from the input stream until and including delim. (this is possibly a duplicate of Why does std::basic_istream::ignore() extract more characters than specified?, however my specific case doesn't deal with the delim) In EOF state, if not, the character it peeked at will be the next one you read). , it's looking for EOF, and if it doesn't find it after two characters, it must read one more to see if it shows up after the ignored characters (if it does, it'll leave Since you didn't provide an end character for In EOF state, or leaving the next character in the buffer for the next read otherwise): Terminates because it's read the number of characters requested, itĪttempts to reads one more character, because it needs to know if condition 2 might also be true (it happened to read the last character so it can take the appropriate action, putting
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