Re: [Boost-users] Question about pool.

On 9/6/07, 蹬三轮的 wrote:

...

According to the description of pool, it should be working like you said. But actually it is not the same. Hereby, there are two cases provided. I think you will find two totally different results between them.

Okay, I have found the problem. pool::alloc_size seems to be a least common multiple of sizeof(void*) and your chunk size.

Assuming sizeof(void*) is 4, In the case of 1316, this comes to 1316. In the case of 1317, this comes to 5268, or 4 times the requested size which is what you are seeing. This seems incorrect.

I have not tested this, but on line 183 of boost/pool/pool.hpp, change

return details::pool::lcm(requested_size, min_size);

to:

return std::max(requested_size + (min_size - 1) & ~(min_size - 1), min_size);

This should fix your size problem while still keeping the size aligned on pointer-sized boundaries, which I believe was the original intention of the author. Does Stephen Cleary even monitor this list to comment? I would also like to hear a comment from Stephen. Anyway, reading

Cory Nelson 7.9.2007 5:13: through "concepts" in pool docs, it seems that the least common multiple is used to ensure proper alignment (if you ever got a SIGBUS, you'll want to avoid unaligned memory access). So beware.... Cheers, Filip