Re: Hidden Features and Dark Corners of C++/STL
On Nov 5, 8:45 pm, Pertulator <igor....@gmail.com> wrote:
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;}
Why don't write ScopeGuard this way:
int main()
{
{
foo const f();
std::printf("got a scope guard f(%p)\n", &f);
}
return 0;
}
Because the type of foo is a base class with no virtual destructor
(for efficiency) and there are different types of scope guards
possible.
As I understand it this trick will be made redundant by C++0x's `auto`
keyword.
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