Re: Exception Safe Code - RAII
Hi,
On 24 Mrz., 20:04, Frank Birbacher <bloodymir.c...@gmx.net> wrote:
Hi!
SchmidtDuesh...@freenet.de schrieb:
ScopeGuardImpl1( const ScopeGuardImpl1& other )
: func_( other.func_ )
, parm_( other.parm_ )
{ }
Why is copying allowed? Why is the base class default constructor used
here (= why isn't the base class copy ctor called)?
The standard requires the copy-ctor (so the compiler does) for
providing a reference to a temporary (by coincidence there is another
thread discussing this item). The missing copy-ctor of the base-class
is a sloppy implementation (thanks). Errors don't raise in this
context because the copy-ctor isn't used by the compiler (it just has
to be there).
VS2008 compiles and links successfully if the copy-ctor is just
declared. I don't know if this is an option.
typedef const ScopeGuardImplBase& ScopeGuard;
Attention: Some weeks ago I trapped into a bug with MSVC Express 8 or 9
(that is .NET 2005 or 2008 respectively) using references to
temporaries. MSVC would destroy the temporary early instead of extending
its lifetime to the lifetime of the reference variable.
Seems to work in VS2008.
The way the template parameter "Func" is used cannot express the nothrow
intent of the function. Yes, one can make the dtor "throw()", ...
I thought you have to ('dtors never throw').
ScopeGuardImpl1::~ScopeGuardImpl1() //thow()
{
try {
if ( ! dismissed() ) func_( parm_ );
}
catch (...) {
}
}
This will silently ignore any exception, which is really bad. If a
ScopeGuard cannot do its cleanup properly then the function using it
cannot fulfill its purpose and continuing the program can be really
desasterous. Instead call "abort()" to make the program halt instantly.
Yep. The user of ScopeGuard has to think about cleanup, which
shouldn't throw.
If it does, a graceful program-termination may be best.
Thank you.
Kasimir
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