Re: Hidden Features and Dark Corners of C++/STL

From:

Pertulator <igor.sol@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Thu, 5 Nov 2009 12:45:51 CST

Message-ID:

<8e5c8659-a296-4547-917b-1eb0d86b6211@d5g2000yqm.googlegroups.com>

On Oct 30, 1:08 am, "Chris M. Thomasson" <n...@spam.invalid> wrote:

"Vladimir Jovic" <vladasp...@gmail.com> wrote in message

news:hcbd84$t24$1@news.albasani.net...> Goran wrote:

By now probably everyone know this one, but it was a major revelation
for me at the time: when a temporary is assigned to a reference inside
a {} block, it's lifetime is extended to the lifetime of a reference.
That made ScopeGuard possible. ScopeGuard FTW!

Do you mean something like in the next example?

[...]
_______________________________________________________________
#include <cstdio>

struct foo
{
    foo()
    {
        std::printf("(%p)->foo::foo()\n",
                    (void*)this);
    }

    ~foo()
    {
        std::printf("(%p)->foo::~foo()\n",
                    (void*)this);
    }

};

foo
make_foo()
{
    return foo();

}

int
main()
{
    {
        foo const& f = make_foo();

        std::printf("got a const reference to f(%p)\n",
                    (void*)&f);
    }

    return 0;}

_______________________________________________________________

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Why don't write ScopeGuard this way:

int main()
{
     {
         foo const f();
         std::printf("got a scope guard f(%p)\n", &f);
     }
     return 0;
}

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