Re: catch exception
On Aug 24, 2:24 am, junw2...@gmail.com wrote:
On Aug 22, 2:57 pm, gpderetta <gpdere...@gmail.com> wrote:
On Aug 22, 11:15 pm, junw2...@gmail.com wrote:
class A
{
public:
A()
{
try
{
p = new int;
//Other lines that may throw exception.
}
catch(...)
{
delete p;
}
private:
int *p;
};
If 'new int' throws, you'll be deleting an uninitialized pointer which
is UB.
It is safer and simpler to use a smart pointer.
In fact, smart pointer will also delete p.
The smart pointer will not delete 'p', 'p' will be the smart pointer :
struct A() {
A() p(new int) { /* do something with p */ }
private:
std::auto_ptr<int> p;
};
Theoretically, they are the
same, rigth?
Wrong. If 'new int' trows, the smart pointer won't have been
constructed yet, so its destructor won't be called.
OTOH, if you instead reset p to 'new int' in the body of the
constructor, the smart pointer will have been default constructed. If
'new int' throws, p destructor will be called, but destroying a
default constructed smart pointer will not lead to UB (well, at least
for any reasonable smart pointer).
In general, the less you use try/catch, the easier is not to make
mistakes. RAII is your friend.
HTH,
--
gpd