CODEWITHSUNDEEP
c++boost
codekiddy
codekiddy

Reputation: 6137

usage of make_shared and allocate_shared in boost?

I'm not able to understand the boost documentation on how to use make_shared and allocate_shared to initialize shared arrays and pointers:

shared_ptr<int> p_int(new int); // OK
shared_ptr<int> p_int2 = make_shared<int>(); // OK
shared_ptr<int> p_int3 = allocate_shared(int);  // ??


shared_array<int> sh_arr(new int[30]); // OK
shared_array<int> sh_arr2 = make_shared<int[]>(30); // ??
shared_array<int> sh_arr3 = allocate_shared<int[]>(30); // ??

I'm trying to learn the correct syntax to initialize the above variables commented as // ??

Upvotes: 2

Views: 3235

Answers (1)

T.C.
T.C.

Reputation: 137310

allocate_shared is used just like make_shared, except that you pass an allocator as the first argument. 

boost::shared_ptr<int> p_int(new int);
boost::shared_ptr<int> p_int2 = boost::make_shared<int>();

MyAllocator<int> alloc;
boost::shared_ptr<int> p_int3 = boost::allocate_shared<int>(alloc);

There is no make function for boost::shared_array, so the only way to make one is allocating the memory manually:

boost::shared_array<int> sh_arr(new int[30]);

But boost::make_shared etc. support array types - either one of unknown size, or one of fixed size - in both cases a boost::shared_ptr is returned:

boost::shared_ptr<int[]> sh_arr2 = boost::make_shared<int[]>(30);
boost::shared_ptr<int[30]> sh_arr3 = boost::make_shared<int[30]>();

Note that std::shared_ptr does not support arrays at this time.

Upvotes: 7

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