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423. Effects of negativestreamsize in iostreams
Section: 31 [input.output] Status: Open Submitter: Martin Sebor Opened: 2003-09-18 Last modified: 2018-12-09
Priority: 3
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Discussion:
A third party test suite tries to exercise istream::ignore(N) with a negative value of N and expects that the implementation will treat N as if it were 0. Our implementation asserts that (N >= 0) holds and aborts the test.
I can't find anything in section 27 that prohibits such values but I don't see what the effects of such calls should be, either (this applies to a number of unformatted input functions as well as some member functions of the basic_streambuf template).
[ 2009-07 Frankfurt ]
This is related to LWG 255(i).
Move to NAD Future.
[LEWG Kona 2017]
Recommend Open: We agree that we should require N >= 0 for the selected functions
[2018-12-04 Reflector prioritization]
Set Priority to 3
Proposed resolution:
I propose that we add to each function in clause 27 that takes an argument, say N, of type streamsize a Requires clause saying that "N >= 0." The intent is to allow negative streamsize values in calls to precision() and width() but disallow it in calls to streambuf::sgetn(), istream::ignore(), or ostream::write().
[Kona: The LWG agreed that this is probably what we want. However, we need a review to find all places where functions in clause 27 take arguments of type streamsize that shouldn't be allowed to go negative. Martin will do that review.]
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