On Tue, 11 Nov 2025 14:11:28 GMT, Harald Eilertsen <[email protected]> wrote:
> `jdk.internal.foreign.SegmentFactories::allocateNativeInternal` assumes that > the underlying implementation of malloc aligns allocations on 16 byte > boundaries for 64 bit platforms, and 8 byte boundaries on 32 bit platforms. > So for any allocation where the requested alignment is less than or equal to > this default alignment it makes no adjustment. > > However, this assumption does not hold for all allocators. Specifically > jemallc, used by libc on FreeBSD will align small allocations on 8 or 4 byte > boundaries, respectively. This causes allocateNativeInternal to sometimes > return memory that is not properly aligned when the requested alignment is > exactly 16 bytes. > > To make sure we honour the requested alignment when it exaclty matches the > quantum as defined by MAX_MALLOC_ALIGN, this patch ensures that we adjust the > alignment also in this case. > > This should make no difference for platforms where malloc allready aligns on > the quantum, except for a few unnecessary trivial calculations. > > This work was sponsored by: The FreeBSD Foundation This pull request has now been integrated. Changeset: 10ba0ab3 Author: Harald Eilertsen <[email protected]> Committer: Jorn Vernee <[email protected]> URL: https://git.openjdk.org/jdk/commit/10ba0ab3c0017858bafb65b49a4cadd9a0351fb4 Stats: 10 lines in 2 files changed: 8 ins; 0 del; 2 mod 8371637: allocateNativeInternal sometimes return incorrectly aligned memory Co-authored-by: Kurt Miller <[email protected]> Reviewed-by: mcimadamore, jvernee ------------- PR: https://git.openjdk.org/jdk/pull/28235
