Re: Threadsafe singletons

From:

"kanze" <kanze@gabi-soft.fr>

Newsgroups:

comp.lang.c++.moderated,comp.programming.threads

Date:

2 Aug 2006 08:42:23 -0400

Message-ID:

<1154512576.579713.208610@i3g2000cwc.googlegroups.com>

Matthias Hofmann wrote:

"kanze" <kanze@gabi-soft.fr> schrieb im Newsbeitrag
news:1154432716.097639.127800@b28g2000cwb.googlegroups.com...

What could happen? The only thing I can imagine is using
the char pointer to modify the string literal. This can be
fixed by using a pointer to a const char.

    void
    muckItUp()
    {
        char doh[] = "How long will I exist?" ;
        Singleton::GetInstance().SetName( doh ) ;
    }

I wouldn't like to use the singleton after a call to muckItUp.

I see. Would it make a difference if doh' were a pointer to a
char rather than an array, as follows?

char* doh = "Am I located on the stack?";

Obviously. The problem is one of object lifetime; using a char
pointer, instead of std::string, only works if the object
lifetime of the char const[] it points to is static (or strictly
speaking, at least until the next call to SetName. Anytime you
pass the address of a string literal, this condition is met.

David's example is probably more realistic of what will happen
in practice. The user will create the string in an std::string,
and then use c_str() to pass it to SetName.

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