Re: I wish I could make my own keywords

From:
"Chris M. Thomasson" <no@spam.invalid>
Newsgroups:
comp.lang.c++
Date:
Fri, 11 Sep 2009 12:35:39 -0700
Message-ID:
<h8e8o6$uj1$1@news.ett.com.ua>
"Chris Becke" <chris.becke@gmail.com> wrote in message
news:1252681334.274186@vasbyt.isdsl.net...

Think for a moment about the compiler checking const correctness adds.

Then, imagine a c++ with a syntax where we could create our own 'const'
like qualifier keywords.

In a multi threaded development environment one could imagine wanting to
declare a 'threadsafe' qualifier.
declare_qualifier threadsafe;

threadsafe would be a qualifier for methods - methods qualified as
threadsafe would cause compiler errors if they attempted to call non
threadsafe qualified methods.


Humm... I am wondering why it would be an error for a threadsafe method to
call a non-threadsafe method? Think in terms of the following pseudo-code:
_________________________________________________________________
class foo
{
    int m_data;
    mutex m_mutex;

private:
    void prv_add(int data)
    {
        m_data += data;
    }

public:
    void add(int data)
    {
        mutex::guard lock(m_mutex);
        prv_add(data);
    }

    void sub(int data)
    {
        mutex::guard lock(m_mutex);
        prv_add(-data);
    }
};
_________________________________________________________________

I guess one can consider `foo::add/sub()' to be "threadsafe" methods, and
`foo::prv_add()' would be a non-threadsafe method. I see no problems with
this setup in which threadsafe methods calls a non-threadsafe method to do
the actual work. In fact, it's a fairly common technique that gets around
the need for nasty recursive mutexs...

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