[PATCH] streambuf_iterator: avoid debug-dependent behaviour

[François Dumont]

Hi

     Completing the execution of tests revealed a lot about the current 
implementation.

     The main point of current implementation is to delay as much as 
possible the capture of the current streambuf position. So my original 
proposal capturing state on instantiation was wrong.

     This new proposal concentrate on the debug-dependent code. Debug 
assertions now avoids calling _M_at_eof() which also capture iterator 
state. It also simplifies _M_get() method a little bit like Petr 
proposed but keeping the _M_sbuf reset when reaching eof. Thanks to this 
work I realized that std::find specialization could also be simplified 
by returning a streambuf_iterator which will capture current streambuf 
state on evaluation.

      Note that I haven't been able to create a test case revealing the 
problem. This is more a code quality issue as current code violates the 
principal that debug asserts shouldn't impact object state. AFAIK this 
is noticeable only under gdb.

     Regarding avoiding the reset of _M_sbuf it might be possible,your 
test case could be a good reason to do so. But this is going to be a big 
change for current implementation so don't forget to run all testsuite 
and to consider the std::copy and std::find specializations.

Tested under Linux x86_64, normal and debug modes.

Ok to commit ?

François


On 08/09/2017 07:47, Petr Ovtchenkov wrote:
> -gcc-patches
>
> On Thu, 7 Sep 2017 23:02:15 +0200
> François Dumont <frs.dumont@gmail.com> wrote:
>
>> +	_M_c = _M_sbuf->sgetc();
>> +	if (_S_at_eof(_M_c))
>> +	  _M_sbuf = 0;
> _M_sbuf = 0; <--- Is not what I axpect here.
>
> Suggestions will be later, after we finish copyright assignment for
> changes procedure (in progress).
>
> WBR,
>
> --
>
>     - ptr
>

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