[jira] Updated: (STDCXX-914) sstream ctors inefficient in reentrant modes

["Martin Sebor (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/STDCXX-914?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Martin Sebor updated STDCXX-914:
--------------------------------

    Attachment: stdcxx-914.gprof

Attached full gprof output for a library and test both compiled with {{-D_RWSTD_USE_STRING_ATOMIC_OP}} on the command line (see STDCXX-162).

> sstream ctors inefficient in reentrant modes
> --------------------------------------------
>
>                 Key: STDCXX-914
>                 URL: https://issues.apache.org/jira/browse/STDCXX-914
>             Project: C++ Standard Library
>          Issue Type: Improvement
>          Components: 27. Input/Output
>    Affects Versions: 4.1.2, 4.1.3, 4.1.4, 4.2.0, 4.2.1
>            Reporter: Martin Sebor
>            Priority: Critical
>             Fix For: 4.2.2
>
>         Attachments: stdcxx-914.gprof
>
>   Original Estimate: 12h
>  Remaining Estimate: 12h
>
> As discussed in this [thread|http://markmail.org/message/hqlsw5dq23gx7d4o] stream ctors in thread-safe builds are inefficient due to the initialization of the mutex data member in every stream, even in those that never use it. As soon as binary compatibility rules permit it we should remove the mutex and/or defer its initialization until it's needed. It might be possible to implement the deferred initialization as early as 4.2.2, or maybe 4.3. Complete removal will need to wait until 5.0.

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