[PATH 3/3] libstdc++: Add std::advance ostreambuf_iterator overload

[Jonathan Wakely]

On 14/09/20 22:36 +0200, François Dumont via Libstdc++ wrote:
>On 10/09/20 5:19 pm, Jonathan Wakely wrote:
>>On 09/09/20 22:12 +0200, François Dumont via Libstdc++ wrote:
>>>libstdc++: Add std::advance overload for ostreambuf_iterator
>>>
>>>Implement std::advance overload for ostreambuf_iterator using 
>>>basic_streambuf
>>>pubseekof.
>>>
>>>libstdc++-v3/ChangeLog:
>>>
>>>        * include/bits/streambuf_iterator.h 
>>>(ostreambuf_iterator): Add
>>>        std::advance friend declaration.
>>>        (advance(ostreambuf_iterator<>&, _Distance)): New.
>>>        * 
>>>testsuite/25_algorithms/advance/ostreambuf_iterator/char/1.cc:
>>>        New test.
>>>        * 
>>>testsuite/25_algorithms/advance/ostreambuf_iterator/char/1_neg.cc:
>>>        New test.
>>>        * 
>>>testsuite/25_algorithms/advance/ostreambuf_iterator/char/2.cc:
>>>        New test.
>>>        * 
>>>testsuite/25_algorithms/advance/ostreambuf_iterator/char/2_neg.cc:
>>>        New test.
>>>
>>>Tested under Linux x85_64.
>>>
>>>Ok to commit ?
>>
>>I think relying on seeking here is a bad idea for the same reason as
>>in my previous email. We don't know what seek does for an arbitrary
>>derived streambuf, or even if it is possible at all.
>>
>>
>After having implementing it similarly to the overload on 
>istreambuf_iterator I wrote a test to compare the std;;advance 
>behavior with a manual increment. And so I realized that incrementing 
>a ostreambuf_iterator is a no-op and so must be the std::advance 
>unless you tell otherwise.
>
>There was a reason for this overload to be missing.

OK, good to know.