Deprecate inclusion of <sys/sysmacros.h> by <sys/types.h>

The macros defined by <sys/sysmacros.h> are not part of POSIX nor XSI, and
their names frequently collide with user code; see for instance glibc bug
19239 and Red Hat bug 130601.  <stdlib.h> includes <sys/types.h> under
_GNU_SOURCE, and C++ code presently cannot avoid being compiled under
_GNU_SOURCE, exacerbating the problem.

	* NEWS: Inclusion of <sys/sysmacros.h> by <sys/types.h> is deprecated.
	* misc/sys/sysmacros.h: If __SYSMACROS_DEPRECATED_INCLUSION is defined,
	define major, minor, and makedev to issue deprecation warnings on use.
	If __SYSMACROS_DEPRECATED_INCLUSION is *not* defined, suppress
	previously-activated deprecation warnings for these macros and prevent
	subsequent inclusions of this header from having any effect.
	* posix/sys/types.h: Define __SYSMACROS_DEPRECATED_INCLUSION before
	including <sys/sysmacros.h>, and undefine it again afterward.

4 files changed, 88 insertions, 4 deletions

diff --git a/ChangeLog b/ChangeLog
index d6a3078..a261ada 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,17 @@
 2016-08-03  Zack Weinberg  <zackw@panix.com>
 
+	[BZ #19239]
+	* NEWS: Inclusion of <sys/sysmacros.h> by <sys/types.h> is deprecated.
+	* misc/sys/sysmacros.h: If __SYSMACROS_DEPRECATED_INCLUSION is defined,
+	define major, minor, and makedev to issue deprecation warnings on use.
+	If __SYSMACROS_DEPRECATED_INCLUSION is *not* defined, suppress
+	previously-activated deprecation warnings for these macros and prevent
+	subsequent inclusions of this header from having any effect.
+	* posix/sys/types.h: Define __SYSMACROS_DEPRECATED_INCLUSION before
+	including <sys/sysmacros.h>, and undefine it again afterward.
+
+2016-08-03  Zack Weinberg  <zackw@panix.com>
+
 	* sysdeps/generic/sys/sysmacros.h: Delete file.
 	* sysdeps/unix/sysv/linux/makedev.c: Delete file.
 	* sysdeps/unix/sysv/linux/sys/sysmacros.h: Move file ...
diff --git a/NEWS b/NEWS
index 495bde0..25c771d 100644
--- a/NEWS
+++ b/NEWS
@@ -17,6 +17,16 @@ Version 2.25
   from that TS.  Note that most features from that TS are not supported by
   the GNU C Library.
 
+* The inclusion of <sys/sysmacros.h> by <sys/types.h> is deprecated.  This
+  means that in a future release, the macros “major”, “minor”, and “makedev”
+  will only be available from <sys/sysmacros.h>.
+
+  These macros are not part of POSIX nor XSI, and their names frequently
+  collide with user code; see for instance glibc bug 19239 and Red Hat bug
+  130601.  <stdlib.h> includes <sys/types.h> under _GNU_SOURCE, and C++ code
+  presently cannot avoid being compiled under _GNU_SOURCE, exacerbating the
+  problem.
+
 Security related changes:
 
   [Add security related changes here]
diff --git a/misc/sys/sysmacros.h b/misc/sys/sysmacros.h
index dc2eb83..086e9af 100644
--- a/misc/sys/sysmacros.h
+++ b/misc/sys/sysmacros.h
@@ -16,6 +16,23 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#ifndef _SYS_SYSMACROS_H_OUTER
+
+#ifndef __SYSMACROS_DEPRECATED_INCLUSION
+# define _SYS_SYSMACROS_H_OUTER 1
+#endif
+
+/* If <sys/sysmacros.h> is included after <sys/types.h>, these macros
+   will already be defined, and we need to redefine them without the
+   deprecation warnings.  (If they are included in the opposite order,
+   the outer #ifndef will suppress this entire file and the macros
+   will be usable without warnings.)  */
+#undef major
+#undef minor
+#undef makedev
+
+/* This is the macro that must be defined to satisfy the misuse check
+   in bits/sysmacros.h. */
 #ifndef _SYS_SYSMACROS_H
 #define _SYS_SYSMACROS_H 1
 
@@ -23,32 +40,65 @@
 #include <bits/types.h>
 #include <bits/sysmacros.h>
 
+/* The extra "\n " moves gcc's [-Wdeprecated-declarations] annotation
+   onto the next line.  */
+#define __SYSMACROS_DEPRECATION_MSG(symbol)				     \
+  "\n  In the GNU C Library, `" #symbol "' is defined by <sys/sysmacros.h>." \
+  "\n  For historical compatibility, it is currently defined by"	     \
+  "\n  <sys/types.h> as well, but we plan to remove this soon."		     \
+  "\n  To use `" #symbol "', include <sys/sysmacros.h> directly."	     \
+  "\n  If you did not intend to use a system-defined macro `" #symbol "',"   \
+  "\n  you should #undef it after including <sys/types.h>."		     \
+  "\n "
+
 #define __SYSMACROS_DECL_TEMPL(rtype, name, proto)			     \
   extern rtype gnu_dev_##name proto __THROW __attribute_const__;
 
+#define __SYSMACROS_FST_DECL_TEMPL(rtype, name, proto)			     \
+  extern rtype __REDIRECT_NTH (__##name##_from_sys_types, proto,	     \
+			       gnu_dev_##name)				     \
+       __attribute_const__						     \
+       __attribute_deprecated_msg__ (__SYSMACROS_DEPRECATION_MSG (name));
+
 #define __SYSMACROS_IMPL_TEMPL(rtype, name, proto)			     \
   __extension__ __extern_inline __attribute_const__ rtype		     \
   __NTH (gnu_dev_##name proto)
 
+#define __SYSMACROS_FST_IMPL_TEMPL(rtype, name, proto)			     \
+  __extension__ __extern_inline __attribute_const__ rtype		     \
+  __NTH (__##name##_from_sys_types proto)
+
 __BEGIN_DECLS
 
 __SYSMACROS_DECLARE_MAJOR (__SYSMACROS_DECL_TEMPL)
 __SYSMACROS_DECLARE_MINOR (__SYSMACROS_DECL_TEMPL)
 __SYSMACROS_DECLARE_MAKEDEV (__SYSMACROS_DECL_TEMPL)
 
+__SYSMACROS_DECLARE_MAJOR (__SYSMACROS_FST_DECL_TEMPL)
+__SYSMACROS_DECLARE_MINOR (__SYSMACROS_FST_DECL_TEMPL)
+__SYSMACROS_DECLARE_MAKEDEV (__SYSMACROS_FST_DECL_TEMPL)
+
 #ifdef __USE_EXTERN_INLINES
 
 __SYSMACROS_DEFINE_MAJOR (__SYSMACROS_IMPL_TEMPL)
 __SYSMACROS_DEFINE_MINOR (__SYSMACROS_IMPL_TEMPL)
 __SYSMACROS_DEFINE_MAKEDEV (__SYSMACROS_IMPL_TEMPL)
 
+__SYSMACROS_DEFINE_MAJOR (__SYSMACROS_FST_IMPL_TEMPL)
+__SYSMACROS_DEFINE_MINOR (__SYSMACROS_FST_IMPL_TEMPL)
+__SYSMACROS_DEFINE_MAKEDEV (__SYSMACROS_FST_IMPL_TEMPL)
+
 #endif
 
 __END_DECLS
 
+#endif /* _SYS_SYSMACROS_H */
+
 #ifndef __SYSMACROS_NEED_IMPLEMENTATION
 # undef __SYSMACROS_DECL_TEMPL
+# undef __SYSMACROS_FST_DECL_TEMPL
 # undef __SYSMACROS_IMPL_TEMPL
+# undef __SYSMACROS_FST_IMPL_TEMPL
 # undef __SYSMACROS_DECLARE_MAJOR
 # undef __SYSMACROS_DECLARE_MINOR
 # undef __SYSMACROS_DECLARE_MAKEDEV
@@ -57,8 +107,14 @@ __END_DECLS
 # undef __SYSMACROS_DEFINE_MAKEDEV
 #endif
 
-#define major(dev) gnu_dev_major (dev)
-#define minor(dev) gnu_dev_minor (dev)
-#define makedev(maj, min) gnu_dev_makedev (maj, min)
+#ifdef __SYSMACROS_DEPRECATED_INCLUSION
+# define major(dev) __major_from_sys_types (dev)
+# define minor(dev) __minor_from_sys_types (dev)
+# define makedev(maj, min) __makedev_from_sys_types (maj, min)
+#else
+# define major(dev) gnu_dev_major (dev)
+# define minor(dev) gnu_dev_minor (dev)
+# define makedev(maj, min) gnu_dev_makedev (maj, min)
+#endif
 
 #endif /* sys/sysmacros.h */
diff --git a/posix/sys/types.h b/posix/sys/types.h
index a728567..83dadcd 100644
--- a/posix/sys/types.h
+++ b/posix/sys/types.h
@@ -218,8 +218,14 @@ typedef int register_t __attribute__ ((__mode__ (__word__)));
 /* It also defines `fd_set' and the FD_* macros for `select'.  */
 # include <sys/select.h>
 
-/* BSD defines these symbols, so we follow.  */
+/* BSD defines `major', `minor', and `makedev' in this header.
+   However, these symbols are likely to collide with user code, so we are
+   going to stop defining them here in an upcoming release.  Code that needs
+   these macros should include <sys/sysmacros.h> directly.  Code that does
+   not need these macros should #undef them after including this header.  */
+# define __SYSMACROS_DEPRECATED_INCLUSION
 # include <sys/sysmacros.h>
+# undef __SYSMACROS_DEPRECATED_INCLUSION
 #endif /* Use misc.  */