On 12/28/2016 11:07 AM, Peter Maydell wrote: > On 28 December 2016 at 16:10, Eric Blake <ebl...@redhat.com> wrote: >> On 12/28/2016 08:53 AM, Christopher Covington wrote: >>> The definition of the major() and minor() macros are moving within glibc to >>> <sys/sysmacros.h>. Include this header to avoid the following sorts of >>> build-stopping messages:
>> Works for glibc; but <sys/sysmacros.h> is non-standard and not present >> on some other systems, so this may fail to build elsewhere. You'll >> probably need a configure probe. Autoconf also says that some platforms >> have <sys/mkdev.h> instead of <sys/sysmacros.h> (per its AC_HEADER_MAJOR >> macro). > > Also this seems straightforwardly like a bug in glibc: it shouldn't > be making this kind of breaking change. makedev(3) on my Linux box > says nothing about needing sysmacros.h for these. Here's the bug explaining the rationale behind the change: https://sourceware.org/bugzilla/show_bug.cgi?id=19239 It IS a bug fix, but in the other direction - it is fixing namespace pollution that was present in <sys/types.h> and breaking certain standard-required idioms. There HAS been warning, but system man pages have not always been updated to track upstream development, and the plan was that glibc 2.25 only causes a warning rather than outright failure to compile (although with -Werror, you have to adjust right away, rather than when the future glibc actually changes <sys/types.h> again to completely drop the pollution). It is CORRECT to fix any software relying on makedev() to use the CORRECT headers for that declaration, rather than getting it for free from <sys/types.h> pollution - the problem is that makedev() is not portable, and therefore the spelling of the correct header is not trivial - it requires some configure-time probing. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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