Remove FIXME #2699---I believe the calculation is correct. Fixes #2699. #6053
Conversation
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It seems like it could be wrong if the header alignment was smaller than the body alignment. However... the header is 4 words so that's pretty unlikely to be true on any architecture. |
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@thestinger maybe I'm being dense, but why does the alignment of the header matter? Also, the alignment is not a function of its size, right? so the alignment of the header will just be the ptr alignment, basically. |
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@nikomatsakis: well I'm assuming that I don't know where/how this is used so that might not matter. |
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Ah, I think you are saying that the total size of the struct would be larger than what this function returns, which is true. I noticed |
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I cannot tell whether the original comment was unsure about the arithmetic calculations, or if it was unsure about the assumptions being made about the alignment of the current allocation pointer. The arithmetic calculation looks fine to me, though. This technique is documented e.g. in Henry Warren's "Hacker's Delight" (section 3-1). (I am sure one can find it elsewhere too, its not an obscure property.)
r? @jld or @graydon
The calculation looks right to me, but perhaps one of you two can double check. You two seem like you are doing the most recent work in this sort of area.