Minimize sysdeps code involved in defining major/minor/makedev.

Presently sys/sysmacros.h is entirely defined in sysdeps.  This would
mean that the deprecation logic coming up in the next patch would have
to be written twice (in generic/ and unix/sysv/linux/).  To avoid that,
hoist all but the unavoidably system-dependent logic to misc/, leaving a
bits/ header behind.  This also promotes the Linux-specific encoding of
dev_t, which accommodates 32-bit major and minor numbers in a 64-bit dev_t,
to generic, as glibc's dev_t is always 64 bits wide.

The former Linux implementation used inline functions to avoid evaluating
arguments more than once.  After this change, all platforms use inline
functions, which means that three new symbols are added to the generic ABI.
(These symbols are in the user namespace, which is how they have always
been on Linux.  They begin with "gnu_dev_", so collisions with user code
are pretty unlikely.)

New ports henceforth need only provide a bits/sysmacros.h defining
internal macros __SYSMACROS_{DECLARE,DEFINE}_{MAJOR,MINOR,MAKEDEV}.
This is only necessary if the kernel encoding is incompatible with
the now-generic encoding (for instance, it would be necessary for
FreeBSD).

While I was at it, I added a basic round-trip test for these functions.

	* sysdeps/generic/sys/sysmacros.h: Delete file.
	* sysdeps/unix/sysv/linux/makedev.c: Delete file.
	* sysdeps/unix/sysv/linux/sys/sysmacros.h: Move file ...
	* bits/sysmacros.h: ... here; this encoding is now the generic
	encoding.  Now defines only the following macros:
	__SYSMACROS_DECLARE_MAJOR, __SYSMACROS_DEFINE_MAJOR,
	__SYSMACROS_DECLARE_MINOR, __SYSMACROS_DEFINE_MINOR,
	__SYSMACROS_DECLARE_MAKEDEV, __SYSMACROS_DEFINE_MAKEDEV.

	* misc/sys/sysmacros.h, misc/makedev.c: New files that use
	bits/sysmacros.h and the above new macros to generate the
	public implementations of major, minor, and makedev.
	* misc/tst-makedev.c: New test.
	* include/sys/sysmacros.h: New wrapper.

	* misc/Makefile (headers): Add sys/sysmacros.h, bits/sysmacros.h.
	(routines): Add makedev.
	(tests): Add tst-makedev.
	* misc/Versions [GLIBC_2.25]: Add gnu_dev_major, gnu_dev_minor,
	gnu_dev_makedev.
	* posix/Makefile (headers): Remove sys/sysmacros.h.
	* sysdeps/unix/sysv/linux/Makefile (sysdep_routines): Remove makedev.

	* sysdeps/arm/nacl/libc.abilist: Add GLIBC_2.25,
	gnu_dev_major, gnu_dev_makedev, gnu_dev_minor.
	* sysdeps/unix/sysv/linux/aarch64/libc.abilist
	* sysdeps/unix/sysv/linux/alpha/libc.abilist
	* sysdeps/unix/sysv/linux/arm/libc.abilist
	* sysdeps/unix/sysv/linux/hppa/libc.abilist
	* sysdeps/unix/sysv/linux/i386/libc.abilist
	* sysdeps/unix/sysv/linux/ia64/libc.abilist
	* sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
	* sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
	* sysdeps/unix/sysv/linux/microblaze/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
	* sysdeps/unix/sysv/linux/nios2/libc.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
	* sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
	* sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
	* sysdeps/unix/sysv/linux/sh/libc.abilist
	* sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
	* sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
	* sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist
	* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
	* sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist:
	Add GLIBC_2.25.

1 files changed, 3 insertions, 0 deletions

diff --git a/misc/Versions b/misc/Versions
index 671f4870e9..f2c90fffda 100644
--- a/misc/Versions
+++ b/misc/Versions
@@ -152,6 +152,9 @@ libc {
   GLIBC_2.23 {
     # SHLIB_COMPAT(GLIBC_2_0, GLIBC_2_23) used in regexp.c
   }
+  GLIBC_2.25 {
+    gnu_dev_major; gnu_dev_minor; gnu_dev_makedev;
+  }
   GLIBC_PRIVATE {
     __madvise;
     __mktemp;