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From Liviu Nicoara <nikko...@hates.ms>
Subject Re: [jira] [Closed] (STDCXX-1056) std::moneypunct and std::numpunct implementations are not thread-safe
Date Wed, 26 Sep 2012 00:05:41 GMT
On 9/25/12 7:56 PM, Stefan Teleman (JIRA) wrote:
>
>       [ https://issues.apache.org/jira/browse/STDCXX-1056?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Stefan,

I don't think it's ok to close this bug. The race conditions are there and we 
have not come to a completely satisfactory conclusion on how to deal with them, 
or even if we should deal with them. Whichever it is we gotta keep this 
discussion open. I sure hope you want to be a part of it.

FWIW, I have spent quite some time looking at your proposed patch and I am going 
to reopen the incident. If I can.

Liviu

>
> Stefan Teleman closed STDCXX-1056.
> ----------------------------------
>
>      Resolution: Won't Fix
>
> Bug will not be fixed. Upstream refuses to acknowledge the existence of the bug in spite
of objective evidence to the contrary.
>
>> std::moneypunct and std::numpunct implementations are not thread-safe
>> ---------------------------------------------------------------------
>>
>>                  Key: STDCXX-1056
>>                  URL: https://issues.apache.org/jira/browse/STDCXX-1056
>>              Project: C++ Standard Library
>>           Issue Type: Bug
>>           Components: 22. Localization
>>     Affects Versions: 4.2.1, 4.2.x, 4.3.x, 5.0.0
>>          Environment: Solaris 10 and 11, RedHat and OpenSuSE Linux, Sun C++ Compilers
12.1, 12.2, 12.3
>> Issue is independent of platform and/or compiler.
>>             Reporter: Stefan Teleman
>>               Labels: thread-safety
>>              Fix For: 4.2.x, 4.3.x, 5.0.0
>>
>>          Attachments: 22.locale.numpunct.mt.out, facet.cpp.diff, locale_body.cpp.diff,
punct.cpp.diff, runtests-linux32-all.out, runtests-linux64-all.out, runtests.out, STDCXX-1056-additional-timings.tgz,
stdcxx-1056.patch, stdcxx-1056-timings.tgz, stdcxx-4.2.x-numpunct-perfect-forwarding.patch,
stdcxx-4.3.x-numpunct-perfect-forwarding.patch
>>
>>
>> several member functions in std::moneypunct<> and std::numpunct<> return
>> a std::string by value (as required by the Standard). The implication of return-by-value
>> being that the caller "owns" the returned object.
>> In the stdcxx implementation, the std::basic_string copy constructor uses a shared
>> underlying buffer implementation. This shared buffer creates the first problem for
>> these classes: although the std::string object returned by value *appears* to be
owned
>> by the caller, it is, in fact, not.
>> In a mult-threaded environment, this underlying shared buffer can be subsequently
modified by a different thread than the one who made the initial call. Furthermore, two or
more different threads can access the same shared buffer at the same time, and modify it,
resulting in undefined run-time behavior.
>> The cure for this defect has two parts:
>> 1. the member functions in question must truly return a copy by avoiding a call to
the copy constructor, and using a constructor which creates a deep copy of the std::string.
>> 2. access to these member functions must be serialized, in order to guarantee atomicity
>> of the creation of the std::string being returned by value.
>> Patch for 4.2.1 to follow.
>
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