libstdc++/7213: g++ 3.1: basic_filebuf doesn`t support open mode "a+"

[johnb@stl.sarov.ru]

>Number:         7213
>Category:       libstdc++
>Synopsis:       g++ 3.1: basic_filebuf doesn`t support open mode "a+"
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jul 05 01:26:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     johnb@stl.sarov.ru
>Release:        g++ 3.1
>Organization:
>Environment:
Red Hat Linux release 7.2, g++ 3.1, libc 2.2.4
>Description:
basic_filebuf doesn`t support the open mode "a+. See testcase.
>How-To-Repeat:
Compile testcase by g++ 3.1 and run it. For example:
$g++31 open-mode-a+.cpp -o open-mode-a+.exe
$open-mode-a+.exe
You`ll get the "Failed" message.
>Fix:
Add support of "a+" open mode. Probably this is in the file basic_file_stdio.cc
>Release-Note:
>Audit-Trail:
>Unformatted:
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