[PATCH 4/4] Deprecate inclusion of <sys/sysmacros.h> by <sys/types.h>

[Zack Weinberg <zackw at panix dot com>]

The macros defined by <sys/sysmacros.h> are not part of POSIX nor XSI,
and their names have been found frequently to 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.

ChangeLog:
	* 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.
---
 NEWS                 | 15 ++++++++++
 misc/sys/sysmacros.h | 82 +++++++++++++++++++++++++++++++++++++++-------------
 posix/sys/types.h    |  8 ++++-
 3 files changed, 84 insertions(+), 21 deletions(-)

diff --git a/NEWS b/NEWS
index b3fd3cc..e8d3b93 100644
--- a/NEWS
+++ b/NEWS
@@ -33,6 +33,21 @@ Version 2.24
   group: files [SUCCESS=merge] nis
   Implemented by Stephen Gallagher (Red Hat).
 
+* The inclusion of <sys/sysmacros.h> by <sys/types.h> is deprecated.  This
+  means that in a future release, the macros âmajorâ, âminorâ, and âmakedevâ
+  will only be available from <sys/sysmacros.h>.
+
+  The macros defined by <sys/sysmacros.h> are not part of POSIX nor XSI,
+  and their names have been found frequently to 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.
+
+  Code that does not need these macros should #undef them after including
+  <sys/types.h>; this will also improve portability to BSD-derived systems.
+  Code that *does* need these macros should include <sys/types.h>, and then
+  include <sys/sysmacros.h> if __GLIBC__ is defined.
+
 Security related changes:
 
 * An unnecessary stack copy in _nss_dns_getnetbyname_r was removed.  It
diff --git a/misc/sys/sysmacros.h b/misc/sys/sysmacros.h
index edc6bac..3dc6133 100644
--- a/misc/sys/sysmacros.h
+++ b/misc/sys/sysmacros.h
@@ -16,25 +16,59 @@
    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
+# define _SYS_SYSMACROS_H 1
 
-#include <features.h>
-#include <bits/types.h>
-#include <bits/sysmacros.h>
+# include <features.h>
+# include <bits/types.h>
+# include <bits/sysmacros.h>
 
-#define __SYSMACROS_DECL(rtype, name, proto)                            \
-  extern rtype gnu_dev_##name proto __THROW __attribute_const__;
+/* 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 "
 
-#ifdef __USE_EXTERN_INLINES
-# define __SYSMACROS_IMPL(rtype, name, proto, body)             \
-  __SYSMACROS_DECL (rtype, name, proto)                         \
-  __extension__ __extern_inline __attribute_const__ rtype       \
-  __NTH (gnu_dev_##name proto) { body }
-#else
-# define __SYSMACROS_IMPL(rtype, name, proto, expr)    \
-  __SYSMACROS_DECL (rtype, name, proto)
-#endif
+# define __SYSMACROS_DECL(rtype, name, proto)				     \
+   extern rtype gnu_dev_##name proto __THROW __attribute_const__;	     \
+   extern rtype __REDIRECT_NTH (__##name##_from_sys_types, proto,	     \
+				gnu_dev_##name)				     \
+    __attribute_const__							     \
+    __attribute_deprecated_msg__ (__SYSMACROS_DEPRECATION_MSG (name));
+
+# ifdef __USE_EXTERN_INLINES
+#  define __SYSMACROS_IMPL(rtype, name, proto, body)			     \
+    __SYSMACROS_DECL (rtype, name, proto)				     \
+    __extension__ __extern_inline __attribute_const__ rtype		     \
+    __NTH (gnu_dev_##name proto) { body }				     \
+    __extension__ __extern_inline __attribute_const__ rtype		     \
+    __NTH (__##name##_from_sys_types proto) { body }
+# else
+#  define __SYSMACROS_IMPL(rtype, name, proto, expr)			     \
+    __SYSMACROS_DECL (rtype, name, proto)
+# endif
 
 __BEGIN_DECLS
 
@@ -46,11 +80,19 @@ __SYSMACROS_IMPL (__dev_t, makedev,
 
 __END_DECLS
 
-#undef __SYSMACROS_IMPL
-#undef __SYSMACROS_DECL
+# undef __SYSMACROS_IMPL
+# undef __SYSMACROS_DECL
+
+# endif /* _SYS_SYSMACROS_H */
 
-#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.  */
 
 
-- 
2.8.1