--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
 2008-06-17  Eric Blake  <ebb9@byu.net>
 
+	Simplify c-stack prerequisites.
+	* lib/c-stack.c (includes): Remove unused <sys/resource.h>.
+	* m4/c-stack.m4 (AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC): Posix 200x
+	no longer requires <ucontext.h> to exist.  Optimize setrlimit
+	check.
+	(gl_PREREQ_C_STACK): Remove check for unused getcontext and
+	<sys/resource.h>.
+
 	Move c-stack test into testsuite.
 	* modules/c-stack-tests: New file.
 	* lib/c-stack.c [DEBUG]: Move test program...

--- a/lib/c-stack.c
+++ b/lib/c-stack.c
@@ -57,16 +57,8 @@
 #include <stdlib.h>
 #include <string.h>
 
-#if HAVE_SYS_RESOURCE_H
-/* Include sys/time.h here, because...
-   SunOS-4.1.x <sys/resource.h> fails to include <sys/time.h>.
-   This gives "incomplete type" errors for ru_utime and tu_stime.  */
-# if HAVE_SYS_TIME_H
-#  include <sys/time.h>
-# endif
-# include <sys/resource.h>
-#endif
-
+/* Posix 2001 declares ucontext_t in <ucontext.h>, Posix 200x in
+   <signal.h>.  */
 #if HAVE_UCONTEXT_H
 # include <ucontext.h>
 #endif

--- a/m4/c-stack.m4
+++ b/m4/c-stack.m4
@@ -1,16 +1,19 @@
 # Check prerequisites for compiling lib/c-stack.c.
 
-# Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
+# Copyright (C) 2002, 2003, 2004, 2008 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
 
 # Written by Paul Eggert.
 
+# serial 2
+
 AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
   [# for STACK_DIRECTION
    AC_REQUIRE([AC_FUNC_ALLOCA])
-   AC_CHECK_FUNCS(setrlimit)
+   AC_CHECK_FUNCS_ONCE([setrlimit])
+   AC_CHECK_HEADERS_ONCE([ucontext.h])
 
    AC_CACHE_CHECK([for working C stack overflow detection],
      ac_cv_sys_xsi_stack_overflow_heuristic,
@@ -18,7 +21,9 @@
 	[
 	 #include <unistd.h>
 	 #include <signal.h>
-	 #include <ucontext.h>
+	 #if HAVE_UCONTEXT_H
+	 # include <ucontext.h>
+	 #endif
 	 #if HAVE_SETRLIMIT
 	 # include <sys/types.h>
 	 # include <sys/time.h>
@@ -120,9 +125,9 @@
 	a SIGSEGV, and an alternate stack can be established with sigaltstack,
 	and the signal handler is passed a context that specifies the
 	run time stack.  This behavior is defined by POSIX 1003.1-2001
-        with the X/Open System Interface (XSI) option
+	with the X/Open System Interface (XSI) option
 	and is a standardized way to implement a SEGV-based stack
-        overflow detection heuristic.])
+	overflow detection heuristic.])
    fi])
 
 
@@ -132,12 +137,10 @@
    # for STACK_DIRECTION
    AC_REQUIRE([AC_FUNC_ALLOCA])
 
-   AC_CHECK_FUNCS(getcontext sigaltstack)
-   AC_CHECK_DECLS([getcontext], , , [#include <ucontext.h>])
+   AC_CHECK_FUNCS_ONCE([sigaltstack])
    AC_CHECK_DECLS([sigaltstack], , , [#include <signal.h>])
 
-   AC_CHECK_HEADERS_ONCE(sys/time.h unistd.h)
-   AC_CHECK_HEADERS(sys/resource.h ucontext.h)
+   AC_CHECK_HEADERS_ONCE([unistd.h ucontext.h])
 
    AC_CHECK_MEMBERS([struct sigaction.sa_sigaction], , , [#include <signal.h>])