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### 59. Ambiguity in specification of gbump

Section: 29.6.3.4.2 [streambuf.get.area] Status: TC1 Submitter: Matt Austern Opened: 1998-07-28 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

27.5.2.3.1 says that basic_streambuf::gbump() "Advances the next pointer for the input sequence by n."

The straightforward interpretation is that it is just gptr() += n. An alternative interpretation, though, is that it behaves as if it calls sbumpc n times. (The issue, of course, is whether it might ever call underflow.) There is a similar ambiguity in the case of pbump.

(The "classic" AT&T implementation used the former interpretation.)

Proposed resolution:

Change 29.6.3.4.2 [streambuf.get.area] paragraph 4 gbump effects from:

> Effects: Advances the next pointer for the input sequence by n.

to:

> Effects: Adds `n` to the next pointer for the input sequence.

Make the same change to 29.6.3.4.3 [streambuf.put.area] paragraph 4 pbump effects.