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From "Stefan Teleman (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (STDCXX-1056) std::moneypunct and std::numpunct implementations are not thread-safe
Date Sun, 05 Feb 2012 00:25:54 GMT
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
             Fix For: 4.2.x, 4.3.x, 5.0.0


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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