sys_types: avoid glibc 2.25 warnings about major()

glibc 2.25 is deprecating the namespace pollution of <sys/types.h>
injecting major(), minor(), and makedev() into the compilation
environment, with a warning that insists that users include
<sys/sysmacros.h> instead.  However, because the expansion of
AC_HEADER_MAJOR didn't bother checking sys/sysmacros.h until
after probing whether sys/types.h pollutes the namespace, it was
not defining MAJOR_IN_SYSMACROS, with the result that code
compiled with -Werror chokes on the deprecation warnings because
it was not including sysmacros.h.

Backport the autoconf fix (see autoconf commit e17a30e98), so that
gnulib projects avoid the warnings even when using older autoconf.

* m4/sys_types_h.m4 (AC_HEADER_MAJOR): Replace broken version in
older autoconf.
* doc/posix-headers/sys_types.texi (sys/types.h): Document fix.
* doc/glibc-functions/gnu_dev_major.texi (gnu_dev_major): Likewise.
* doc/glibc-functions/gnu_dev_makedev.texi (gnu_dev_makedev): Likewise.
* doc/glibc-functions/gnu_dev_minor.texi (gnu_dev_minor): Likewise.

Signed-off-by: Eric Blake <eblake@redhat.com>

4 files changed, 18 insertions, 0 deletions

diff --git a/doc/glibc-functions/gnu_dev_major.texi b/doc/glibc-functions/gnu_dev_major.texi
index f7a2cfdee4..3a8530089e 100644
--- a/doc/glibc-functions/gnu_dev_major.texi
+++ b/doc/glibc-functions/gnu_dev_major.texi
@@ -6,6 +6,10 @@ Gnulib module: ---
 
 Portability problems fixed by Gnulib:
 @itemize
+The @code{AC_HEADER_MAJOR} macro in Autoconf 2.69 and earlier fails to
+set @code{MAJOR_IN_SYSMACROS} when it detects namespace pollution in
+@file{sys/types.h}; which in turn provokes deprecation warnings in
+glibc 2.25.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/doc/glibc-functions/gnu_dev_makedev.texi b/doc/glibc-functions/gnu_dev_makedev.texi
index febd7f841c..27386985f8 100644
--- a/doc/glibc-functions/gnu_dev_makedev.texi
+++ b/doc/glibc-functions/gnu_dev_makedev.texi
@@ -6,6 +6,10 @@ Gnulib module: ---
 
 Portability problems fixed by Gnulib:
 @itemize
+The @code{AC_HEADER_MAJOR} macro in Autoconf 2.69 and earlier fails to
+set @code{MAJOR_IN_SYSMACROS} when it detects namespace pollution in
+@file{sys/types.h}; which in turn provokes deprecation warnings in
+glibc 2.25.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/doc/glibc-functions/gnu_dev_minor.texi b/doc/glibc-functions/gnu_dev_minor.texi
index a3dbefe344..b4c789cffa 100644
--- a/doc/glibc-functions/gnu_dev_minor.texi
+++ b/doc/glibc-functions/gnu_dev_minor.texi
@@ -6,6 +6,10 @@ Gnulib module: ---
 
 Portability problems fixed by Gnulib:
 @itemize
+The @code{AC_HEADER_MAJOR} macro in Autoconf 2.69 and earlier fails to
+set @code{MAJOR_IN_SYSMACROS} when it detects namespace pollution in
+@file{sys/types.h}; which in turn provokes deprecation warnings in
+glibc 2.25.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/doc/posix-headers/sys_types.texi b/doc/posix-headers/sys_types.texi
index 29bb9ae589..cf44beaf33 100644
--- a/doc/posix-headers/sys_types.texi
+++ b/doc/posix-headers/sys_types.texi
@@ -19,6 +19,12 @@ MSVC 9.
 @item
 The type @code{mode_t} is not defined on some platforms:
 MSVC 9.
+@item
+Some systems leak definitions of @code{major}, @code{minor}, and
+@code{makedev} through this header; however, when
+@file{sys/sysmacros.h} exists, that file should also be included to
+avoid deprecation warnings from the versions in this header:
+glibc 2.25.
 @end itemize
 
 Portability problems not fixed by Gnulib: