memory leak in constructor and during object creation
raj s
class base{
int a;
int *pint;
someclass objsomeclass;
someclass* psomeclass;
base(){
objsomeclass = someclass();
psomeclass = new someclass();
pint = new int();
throw "constructor failed";
a = 43;
}
}
main(){
base temp();
}
in the above code constructor fails.Which objects will be leaked and
how to avoid memory leak and even if destructor is called for
automatic object is temp and temp pointer will leak the memory?
main(){
base *temp = base();
}
what about in the above code and how to avoid memory leak when
constructor fails
Ian Collins
> Will the below code cause memory leak in c++
>
> class base{
> int a;
> int *pint;
> someclass objsomeclass;
> someclass* psomeclass;
> base(){
> objsomeclass = someclass();
> psomeclass = new someclass();
> pint = new int();
> throw "constructor failed";
> a = 43;
> }
> }
> main(){
> base temp();
> }
>
> in the above code constructor fails.Which objects will be leaked and
> how to avoid memory leak and even if destructor is called for
> automatic object is temp and temp pointer will leak the memory?
>
appropriate smart pointer.
> main(){
> base *temp = base();
> }
>
> what about in the above code and how to avoid memory leak when
> constructor fails
There isn't one.
--
Ian Collins.
Old Wolf
> Will the below code cause memory leak in c++
>
> class base{
> int a;
> int *pint;
> someclass objsomeclass;
> someclass* psomeclass;
> base(){
> objsomeclass = someclass();
> psomeclass = new someclass();
> pint = new int();
> throw "constructor failed";
> a = 43;
> }}
Should be a semicolon after this. Now, as
you suspect, if you create a 'base' then
you get a memory leak because the memory
allocated by "new someclass()" and "new int()"
is never freed.
The best solution is to design your class
to not 'new' things. I guess you are coming
from Java or something like that by your code
stype. In C++ you rarely need to have classes
that 'new' their members. For example, in
the above code, there is no need to 'new' an int.
Failing that, you will have to use
'smart pointers' instead of raw pointers.
For example, if instead of:
someclass *psomeclass;
you could have:
auto_ptr<someclass> psomeclass;
Note that you can initialize things in
the constructor initializer list:
base(): psomeclass( new someclass ) {.....}
Some comments on the rest of your code:
>
> main(){
> base temp();
This doesn't declare any objects, it declares
a function. I think you meant:
base temp;
You seem to have a fascination with useless
parentheses :)
Fred Zwarts
If you really must use new and if you cannot use a smart pointer type,
than you should handle the exception yourself. E.g.:
base()
: pint (0), psomeclass (0)
{
try {
objsomeclass = someclass();
psomeclass = new someclass();
pint = new int();
throw "constructor failed";
a = 43;
} catch (...) {
delete pint;
delete psomeclass;
throw;
}
}
Marcel Müller
> Will the below code cause memory leak in c++
Yes. All pointer objects will never be destroyed, since your programm
does not provide a delete statement.
> class base{
> int a;
> int *pint;
> someclass objsomeclass;
> someclass* psomeclass;
> base(){
> objsomeclass = someclass();
> psomeclass = new someclass();
> pint = new int();
> throw "constructor failed";
> a = 43;
> }
> }
> main(){
> base temp();
> }
> in the above code constructor fails.Which objects will be leaked and
> how to avoid memory leak
Use smart pointers.
> and even if destructor is called for
> automatic object is temp and temp pointer will leak the memory?
The destructor will not be called if the constructor fails. But the
destructor for a successfully constructed base members is called -
normally. In your case, you do not catch your exception. That usually
causes a call to abort(), which will end your programm immediately
without any cleanup. From that point it is up to the operating system to
do the cleanup.
> main(){
> base *temp = base();
> }
>
> what about in the above code and how to avoid memory leak when
> constructor fails
The memory of base is normally freed in this case, since no object is
successfully constructed. But again, you must catch your exception to
prevent your programm from an immediate abort.
Marcel