Re: question re. usage of "static" within static member functions of a class

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 8 Sep 2009 14:26:22 -0700 (PDT)
Message-ID:
<f0ed97f9-ea04-4952-88f2-a1982725a0b4@38g2000yqr.googlegroups.com>
On Sep 7, 7:24 am, "Chris M. Thomasson" <n...@spam.invalid> wrote:

"ssb" <s.sharm...@gmail.com> wrote in message

news:97dc452a-f6a5-4a77-9a9c-ea8491d37e40@e4g2000prn.googlegroups.com...

During a code review, I found the following lines of code:


[...]

The "instance" method was implemented as follows:
Data* Data::instance()
{
     static Data* model = new Data();
     return model;
}
I have never come across a situation where a pointer was set
to static in such a case. Is this valid?


It's a singleton.


And to answer the question, it's perfectly valid. A pointer is
an object, just like any other variable, and obeys the same
rules as other variables.

What are the potential pitfalls in such programming practices?


The storage that `model' points to will never be destroyed,
also it's not thread-safe.


Not being destroyed is presumably the reason the code is written
this way. Most of the time, you don't want a singleton to be
destructed. In other word, it's a feature designed to avoid
pitfalls. As for thread-safety, it depends on the
implementation, it is thread safe---modulo bugs---in g++. (But
you're probably right for most implementations.)

--
James Kanze

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