Be my guest to implement these things. I don't think it matters much, and adds a lot of complexity to avoid a single roundup call. And if we have more-strict alignment for glue than ALIGNBYTES, we're already doomed. We don't do that today.
Warner On Tue, Dec 29, 2015 at 3:51 PM, Ian Lepore <i...@freebsd.org> wrote: > On Tue, 2015-12-29 at 11:37 -0800, John Baldwin wrote: > > On Monday, December 28, 2015 01:01:26 PM Warner Losh wrote: > > > I'll look at that, but I don't think posix_memalign is the right > > > way to go. > > > The alignment of FILE is more strict than posix_memalign will > > > return. Ian's > > > idea of __alignof__ is the way to go. We allocate them in one block > > > on > > > purpose for performance, and posix_memalign would be a one at a > > > time affair. > > > > posix_memalign gives you whatever alignment you ask for. Using > > __alignof__ > > to determine the alignment instead of hardcoding sizeof(int64_t) > > would > > certainly be an improvement. If you move the glue after the FILE > > objects > > then you can use posix_memalign() directly as so: > > > > void *mem; > > int error; > > > > error = posix_memalign(&mem, MAX(ALIGNBYTES, > > __alignof__(mbstate_t)), > > n * sizeof(FILE) + sizeof(*g)); > > if (error) > > return (NULL); > > p = (FILE *)mem; > > g = (struct glue *)(p + n); > > g->next = NULL; > > g->niobs = n; > > g->iobs = p; > > ... > > > > (This presumes that the requested alignment of 'struct glue' is less > > than > > the alignment needed by FILE which should be true.) > > > > If there's going to be an assumption that __alignof__(glue) <= > __alignof__(FILE), it might be nice to have a static_assert() of that > to prevent a future time bomb similar to the one that exploded on arm > when it turned out the opposite assumption was wrong. > > -- Ian > > _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
