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c++performancememorymemory-managementvector
kiriloff
kiriloff

Reputation: 26333

c++ memory allocation vector of pointers

I am parallelizing code, thus using structure parallel_vector (ppl). The question would be the same with standard std::vector...

I first build a vectors of pointer to structs. Struct is huge, with primitive types members alongside with huge arrays of primitive type (23000 elements).

I implemented a deep copy copy constructor for this struct.

Then, i access elements in this list in a loop. 

for (int ii=0; ii < nbBlocks; ii++)
{
    MyStruct* Block_temp = list_structs.at( ii );
    // ...
}

When i access element at position ii, am I creating a new object with memory allocation ? should i delete Block_temp at the end of the current loop, or would this destroy the object that is contained in the vector ?

Thanks

Upvotes: 0

Views: 225

Answers (1)

paulm
paulm

Reputation: 5892

You have a pointer to what is already in the vector, the vector seems to own your data, so do not delete it. Copying a pointer is not an allocation.

Consider:

int* a = new int;
int* b = a; // Pretty much what you are doing
delete a; // If you deleted b, then this would be a double delete, and using a or b after that point would be bad

See the docs for std::vector::at

http://www.cplusplus.com/reference/vector/vector/at/

Upvotes: 2

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