Re: Exception Safe Code - RAII
Hi!
SchmidtDueshorn@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)?
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.
Did Andrej forget a 'try..catch'-clause in the D'tor of
ScopeGuardImpl1?
In my example free() can't throw. But the template can be used for any
cleanup-Function.
The way the template parameter "Func" is used cannot express the nothrow
intent of the function. Yes, one can make the dtor "throw()", but
certainly not the way you suggested:
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.
Or just make the dtor "throw()" so any exception will invoke
std::unexpected, which throws again, which in turn will abort the program.
Another way could be to use boost::function<void()throw()>, but it can
throw on construction, which is why you better not use it.
Frank
--
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]