Date: Tue, 25 Apr 2017 08:45:43 +0200 From: Hauke Mehrtens <hauke@...ke-m.de> To: musl@...ts.openwall.com, David Woodhouse <dwmw2@...radead.org>, Felix Janda <felix.janda@...teo.de>, linux-kernel@...r.kernel.org Cc: "David S. Miller" <davem@...emloft.net>, linux-api@...r.kernel.org Subject: Re: Re: [PATCH resent] uapi libc compat: allow non-glibc to opt out of uapi definitions On 03/08/2017 05:39 PM, Carlos O'Donell wrote: > Any header needing compat with a libc includes libc-compat.h (per the > documented way the model works). With this patch any included linux kernel > header that also includes libc-compat.h would immediately define all > the __UAPI_DEF_* constants to 1 as-if it had defined those structures, > but it has not. > > For example, with these two patches applied, the inclusion of linux/if.h > would define __UAPI_DEF_XATTR to 1, but linux/if.h has not defined > XATTR_CREATE or other constants, so a subsequent inclusion sys/xattrs.h > from userspace would _not_ define XATTR_CREATE because __UAPI_DEF_XATTR set > to 1 indicates the kernel has. > > I don't want to read into the model you are proposing and would rather you > document the semantics clearly so we can all see what you mean. What about moving the code from libc-comapt.h into the specific header files? This way including linux/if.h would not have an impact on __UAPI_DEF_XATTR, because this is defined in linux/xattr.h. We would still have a problem when the specific Linux header file gets included before the libc header file, but at least musl does not support this anyway. Hauke
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