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###Bug: wrong allocation size###

I added a few extra int fields to the test class to make it 20 bytes large, and then ran your program. This is the output I saw:

0 created at: 0x1f8dc20
1 created at: 0x1f8dc28
2 created at: 0x1f8dc30
3 created at: 0x1f8dc38

As you can see, each element is only 8 bytes apart instead of 20. In fact, when I filled in the int fields with values, the program quickly died on an assertion failure because I was overwriting the next_free fields of neighboring entries.

###Possible fix###

I changed this line:

 using storage_t = std::aligned_storage<sizeof(T), alignof(T)>;

to this:

 using storage_t = typename std::aligned_storage<sizeof(T), alignof(T)>::type;

and got the following better output (with 24 byte allocations):

0 created at: 0x20e8c20
1 created at: 0x20e8c38
2 created at: 0x20e8c50
3 created at: 0x20e8c68

I'm not a C++ expert. I just looked at the examples from here and here to figure out the above change.

Bug: wrong allocation size

I added a few extra int fields to the test class to make it 20 bytes large, and then ran your program. This is the output I saw:

0 created at: 0x1f8dc20
1 created at: 0x1f8dc28
2 created at: 0x1f8dc30
3 created at: 0x1f8dc38

As you can see, each element is only 8 bytes apart instead of 20. In fact, when I filled in the int fields with values, the program quickly died on an assertion failure because I was overwriting the next_free fields of neighboring entries.

Possible fix

I changed this line:

 using storage_t = std::aligned_storage<sizeof(T), alignof(T)>;

to this:

 using storage_t = typename std::aligned_storage<sizeof(T), alignof(T)>::type;

and got the following better output (with 24 byte allocations):

0 created at: 0x20e8c20
1 created at: 0x20e8c38
2 created at: 0x20e8c50
3 created at: 0x20e8c68

I'm not a C++ expert. I just looked at the examples from here and here to figure out the above change.