sys_random: Work around macOS bug

[Bruno Haible]

On Mac OS X, the header file <sys/random.h> is not self-contained.

On Mac OS X 10.5:

  In file included from ./sys/random.h:28,
                   from ../../gllib/getrandom.c:22:
  /usr/include/sys/random.h:37: error: syntax error before ‘u_int’

It needs <sys/types.h> to be included first.

On Mac OS X 10.13:

  In file included from ../../gllib/getrandom.c:22:
  In file included from ./sys/random.h:28:
  /usr/include/sys/random.h:36:17: error: expected parameter declarator
  __OSX_AVAILABLE(10.12) __IOS_AVAILABLE(10.0) __TVOS_AVAILABLE(10.0) 
__WATCHOS_AVAILABLE(3.0)
                  ^

It needs <stdlib.h> or <unistd.h> to be included first.

This patch provides a workaround.


2020-05-30  Bruno Haible  <bruno@clisp.org>

        sys_random: Work around macOS bug.
        * m4/sys_random_h.m4 (gl_HEADER_SYS_RANDOM): Include <sys/types.h> and
        <stdlib.h> before <sys/random.h>.
        * m4/getrandom.m4 (gl_FUNC_GETRANDOM): Likewise.
        * lib/sys_random.in.h: On macOS, include <sys/types.h> and <stdlib.h>
        first.
        * doc/glibc-headers/sys_random.texi: Mention the macOS problem.

diff --git a/doc/glibc-headers/sys_random.texi 
b/doc/glibc-headers/sys_random.texi
index 1c28595..3f33962 100644
--- a/doc/glibc-headers/sys_random.texi
+++ b/doc/glibc-headers/sys_random.texi
@@ -24,6 +24,9 @@ Portability problems fixed by Gnulib:
 This header file is missing on some platforms:
 glibc 2.24, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 7.1, HP-UX 11.11, IRIX 
6.5, Cygwin, mingw, MSVC 14.
 @item
+This header file is not self-contained on some platforms:
+Mac OS X 10.13.
+@item
 This header file does not declare the @code{getrandom} function on some 
platforms:
 Mac OS X 10.5, FreeBSD 11.0, HP-UX 11.31, Solaris 11.0.
 @end itemize
diff --git a/lib/sys_random.in.h b/lib/sys_random.in.h
index 4d12db9..290fa39 100644
--- a/lib/sys_random.in.h
+++ b/lib/sys_random.in.h
@@ -23,6 +23,14 @@
 
 #if @HAVE_SYS_RANDOM_H@
 
+/* On Mac OS X 10.5, <sys/random.h> assumes prior inclusion of <sys/types.h>.
+   On Max OS X 10.13, <sys/random.h> assumes prior inclusion of a file that
+   includes <Availability.h>, such as <stdlib.h> or <unistd.h>.  */
+# if defined __APPLE__ && defined __MACH__                  /* Mac OS X */
+#  include <sys/types.h>
+#  include <stdlib.h>
+# endif
+
 /* The include_next requires a split double-inclusion guard.  */
 # @INCLUDE_NEXT@ @NEXT_SYS_RANDOM_H@
 
diff --git a/m4/getrandom.m4 b/m4/getrandom.m4
index 9fee059..779c6ad 100644
--- a/m4/getrandom.m4
+++ b/m4/getrandom.m4
@@ -1,4 +1,4 @@
-# getrandom.m4 serial 3
+# getrandom.m4 serial 4
 dnl Copyright 2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -18,8 +18,10 @@ AC_DEFUN([gl_FUNC_GETRANDOM],
       [gl_cv_func_getrandom_ok],
       [AC_COMPILE_IFELSE(
          [AC_LANG_PROGRAM(
-            [[#include <sys/random.h>
+            [[/* Additional includes are needed before <sys/random.h> on Mac 
OS X.  */
               #include <sys/types.h>
+              #include <stdlib.h>
+              #include <sys/random.h>
               ssize_t getrandom (void *, size_t, unsigned int);
             ]],
             [[]])
diff --git a/m4/sys_random_h.m4 b/m4/sys_random_h.m4
index 135d241..c4505b6 100644
--- a/m4/sys_random_h.m4
+++ b/m4/sys_random_h.m4
@@ -1,4 +1,4 @@
-# sys_random_h.m4 serial 2
+# sys_random_h.m4 serial 3
 dnl Copyright (C) 2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -20,6 +20,9 @@ AC_DEFUN([gl_HEADER_SYS_RANDOM],
   dnl corresponding gnulib module is not in use.
   gl_WARN_ON_USE_PREPARE([[
 #if HAVE_SYS_RANDOM_H
+/* Additional includes are needed before <sys/random.h> on Mac OS X.  */
+# include <sys/types.h>
+# include <stdlib.h>
 # include <sys/random.h>
 #endif
     ]],