Problem in allocating an array of objects with no default constructor

[yatko]

Hi,

I want to allocate an array of interprocess_semaphore object
initialized with 0 counter value. This class is a part of boost
library used for thread synchronization.

class interprocess_semaphore {
public:
// construct/copy/destruct
interprocess_semaphore(int);
~interprocess_semaphore();

// public member functions
void post() ;
void wait() ;
bool try_wait() ;
bool timed_wait(const boost::posix_time::ptime &) ;
};

---

interprocess_semaphore* ready_sem;

ready_sem = new interprocess_semaphore[maxFloor;

Since the class has no default constructor, the compiler gives error.
When I try to use vector, I solve the initialization problem. But at
this time, there is another roblem related with copying semaphores.

vector<interprocess_semaphore> ready_sem;

ready_sem.reserve(maxFloor);

for (int i = 0;i < maxFloor; ++i)
ready_sem.push_back(* new boost::interprocess::interprocess_semaphore
(0));

All I want to do is allocating an array of semephore objects with 0
initial counter value. How can I do that in C++ ?

yatko

[alfps]

On 28 Des, 12:01, yatko <yatkonal...@gmail.com> wrote:
>
> vector<interprocess_semaphore> ready_sem;
>
> ready_sem.reserve(maxFloor);
>
> for (int i = 0;i < maxFloor; ++i)
>         ready_sem.push_back(* new boost::interprocess::interprocess_semaphore
> (0));
>
> All I want to do is allocating an array of semephore objects with 0
> initial counter value. How can I do that in C++ ?

Assuming the objects are copyable (copy constructor and assignment
operator),

vector<interprocess_semaphore> ready_sem( maxFloor, 0 );

Cheers & hth.,

- Alf

[amrolla...@gmail.com]

Hi Yatko
I have the following suggestions for you:
1. If semaphore objects usually have initial value (0), it is better
to declare your class
like this:
class interprocess_semaphore {
public:
interprocess_semaphore(int = 0); // default ctor
// as before
};
2. Of course it is not a good idea, but if you like to use array over
vector, you can use the following code:
interprocess_semaphore** ready_sem = new interprocess_semaphore*
[maxFloor];

for (int i = 0; i < maxFloor; i++) {
interprocess_semaphore* p = new interprocess_semaphore(0);
ready_sem[i] = p;
}

// use array ...

for (int i = 0; i < maxFloor; i++) {
delete ready_sem[i];
}

delete [] ready_sem;

Regards,
- Saeed

[yatko]

Hi all,

Thanks for your postings and I am very sorry that less information.

> Hi Yatko
> I have the following suggestions for you:

> 1. If semaphoreobjectsusually have initial value (0), it is better

> to declare your class
> like this:
>   class interprocess_semaphore {
>   public:
>      interprocess_semaphore(int = 0); // default ctor
>      // as before
>   };

First, the interprocess_class is a part of boost library and it is
designed with one-parameter constructor. I could not have the chance
of redeclare the overall class.

> 2. Of course it is not a good idea, but if you like to usearrayover
> vector, you can use the following code:
>         interprocess_semaphore** ready_sem = new interprocess_semaphore*
> [maxFloor];
>
>         for (int i = 0; i < maxFloor; i++) {
>                 interprocess_semaphore* p = new interprocess_semaphore(0);
>                 ready_sem[i] = p;
>         }
>
>         // usearray...
>
>         for (int i = 0; i < maxFloor; i++) {
>                 delete ready_sem[i];
>         }
>
>         delete [] ready_sem;
>
> Regards,
>   - Saeed

Second, I have tried to use vector, but since the class is designed as
noncopyable, the compiler gives errors. Finally, I have decided to use
array of pointers and it works fine.

Thanks