Date: Tue, 29 Oct 2019 19:08:41 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: [PATCH] remaining steps for time64 switchover On Sun, Oct 20, 2019 at 10:46:43PM -0400, Rich Felker wrote: > The attached patch series on top of present git master (commit > 9b2921bea1d5017832e1b45d1fd64220047a9802) should contain all changes > needed for fully working time64 on 32-bit archs, in a form that's > plausibly ready for commit (no makeshift hacks just to get things > demonstrably working). The one omission I'm aware of is what to do > with struct utmpx, which is not actually used at present in any libc > interfaces and thus not part of the ABI surface of libc. That will be > addressed in a separate thread. > > Comments and basic testing are welcome at this point. It should be > possible to build for any of the 32-bit archs, but I have only tested > build for a few and only tested execution on i386 and sh. > > Some useful checks for anyone wanting to help test, especially on the > more obscure archs: > > [...] > > - Does software built against new libc headers basically work? strace breaks at build time with static_assert that IPC_STAT==2. This had me momentarily doubting the whole approach of redefining it rather than making __semctl_time64, etc., but it turns out strace also depends on struct semid_ds, shmid_ds, and msqid_ds matching the kernel layouts, which is impossible with time64, so there's really a fundamental problem here. Fortunately, strace already had the right code and just wasn't using it: if HAVE_SYS_SEM_H, etc. aren't defined in config.h (from autoconf), it falls back to using linux/sem.h, etc., which are exactly what it should have been using all along: the kernel struct layouts and command macro definitions. I think the right patch to strace will be simply removing use of libc sysvipc headers (always using the kernel ones); it doesn't seem practical to write a configure test to determine that the libc ones are usable for parsing the kernel struct. So, first "oh no!" averted! But this may be a preview of what's to come. (And I might have chosen strace as an early test case because I expected things like this.) Rich
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