Hi, On 2022-08-29 11:43:14 -0400, Tom Lane wrote: > Tomas Vondra <tomas.von...@enterprisedb.com> writes: > > I suspect it's a pre-existing bug in Slab allocator, because it does this: > > > #define SlabBlockGetChunk(slab, block, idx) \ > > ((MemoryChunk *) ((char *) (block) + sizeof(SlabBlock) \ > > + (idx * slab->fullChunkSize))) > > > and SlabBlock is only 20B, i.e. not a multiple of 8B. Which would mean > > that even if we allocate block and size the chunks carefully (with all > > the MAXALIGN things), we ultimately slice the block incorrectly. > > Right, same conclusion I just came to. But it's not a "pre-existing" > bug, because sizeof(SlabBlock) *was* maxaligned until David added > another field to it. > > I think adding a padding field to SlabBlock would be a less messy > solution than your patch.
That just seems to invite the same problem happening again later and it's harder to ensure that the padding is correct across platforms. Greetings, Andres Freund
