--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2008-08-16  Eric Blake  <ebb9@byu.net>
+
+	c-stack: fix regression on Irix 5.3 from 2008-06-21
+	* m4/c-stack.m4 (gl_PREREQ_C_STACK): Move check for
+	sa_sigaction...
+	* m4/sigaction.m4 (gl_PREREQ_SIG_HANDLER_H): ...here.
+	(gl_PREREQ_SIGACTION): Depend on sig-handler.h prereq's.
+	* m4/signal_h.m4 (gl_SIGNAL_H_DEFAULTS): Set the default.
+	* modules/signal (Makefile.am): Use the value.
+	* lib/signal.in.h (sa_sigaction) [HAVE_SIGACTION
+	&& !HAVE_STRUCT_SIGACTION_SA_SIGACTION]: Define.
+	* doc/posix-headers/signal.texi (signal.h): Document this
+	portability issue.
+	* doc/posix-functions/sigaction.texi (sigaction): Likewise.
+	Reported by Tom G. Christensen.
+
 2008-08-17  Bruno Haible  <bruno@clisp.org>
 
 	New module 'threadlib'.

--- a/doc/posix-functions/sigaction.texi
+++ b/doc/posix-functions/sigaction.texi
@@ -37,6 +37,11 @@
 mingw.
 
 @item
+In spite of having SA_SIGACTION, struct sigaction lacks the
+sa_sigaction member on some platforms:
+Irix 5.3.
+
+@item
 The symbolic value @code{SIG_IGN} for the @code{SIGCHLD} signal is equivalent
 to a signal handler
 @smallexample

--- a/doc/posix-headers/signal.texi
+++ b/doc/posix-headers/signal.texi
@@ -15,12 +15,13 @@
 @code{struct sigaction} and @code{siginfo_t} are missing on some
 platforms:
 mingw.
+
+@item
+@code{struct sigaction} lacks the @code{sa_sigaction} member on some
+platforms:
+Irix 5.3, Interix 3.5.
 @end itemize
 
 Portability problems not fixed by Gnulib:
 @itemize
-@item
-@code{struct sigaction} lacks the @code{sa_sigaction} member on some
-platforms; this can also be detected by whether @code{SA_SIGINFO} is defined:
-Interix 3.5.
 @end itemize

--- a/lib/signal.in.h
+++ b/lib/signal.in.h
@@ -146,7 +146,11 @@
 extern int sigaction (int, const struct sigaction *restrict,
                       struct sigaction *restrict);
 
-#endif /* !@HAVE_SIGACTION@ */
+#elif !@HAVE_STRUCT_SIGACTION_SA_SIGACTION@
+
+# define sa_sigaction sa_handler
+
+#endif /* !@HAVE_SIGACTION@, !@HAVE_STRUCT_SIGACTION_SA_SIGACTION@ */
 
 
 #ifdef __cplusplus

--- a/m4/c-stack.m4
+++ b/m4/c-stack.m4
@@ -7,7 +7,7 @@
 
 # Written by Paul Eggert.
 
-# serial 3
+# serial 4
 
 AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
   [# for STACK_DIRECTION
@@ -146,8 +146,6 @@
 
    AC_CHECK_HEADERS_ONCE([unistd.h ucontext.h])
 
-   AC_CHECK_MEMBERS([struct sigaction.sa_sigaction], , , [#include <signal.h>])
-
    AC_CHECK_TYPES([stack_t], , , [#include <signal.h>])
 
    dnl c-stack does not need -lsigsegv if the system has XSI heuristics.

--- a/m4/sigaction.m4
+++ b/m4/sigaction.m4
@@ -1,4 +1,4 @@
-# sigaction.m4 serial 3
+# sigaction.m4 serial 4
 dnl Copyright (C) 2008 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -22,6 +22,7 @@
   AC_REQUIRE([gl_SIGNAL_H_DEFAULTS])
   AC_REQUIRE([AC_C_RESTRICT])
   AC_REQUIRE([AC_TYPE_UID_T])
+  AC_REQUIRE([gl_PREREQ_SIG_HANDLER_H])
   AC_CHECK_FUNCS_ONCE([sigaltstack siginterrupt])
   AC_CHECK_TYPES([siginfo_t], [], [], [[
 #include <signal.h>
@@ -36,5 +37,10 @@
 AC_DEFUN([gl_PREREQ_SIG_HANDLER_H],
 [
   AC_REQUIRE([AC_C_INLINE])
-  :
+  AC_CHECK_MEMBERS([struct sigaction.sa_sigaction], , ,
+                   [[#include <signal.h>]])
+  if test $ac_cv_member_struct_sigaction_sa_sigaction = no; then
+    HAVE_STRUCT_SIGACTION_SA_SIGACTION=0
+    AC_SUBST([HAVE_STRUCT_SIGACTION_SA_SIGACTION])
+  fi
 ])

--- a/m4/signal_h.m4
+++ b/m4/signal_h.m4
@@ -1,4 +1,4 @@
-# signal_h.m4 serial 4
+# signal_h.m4 serial 5
 dnl Copyright (C) 2007, 2008 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -26,4 +26,6 @@
   HAVE_SIGSET_T=1;             AC_SUBST([HAVE_SIGSET_T])
   HAVE_SIGINFO_T=1;            AC_SUBST([HAVE_SIGINFO_T])
   HAVE_SIGACTION=1;            AC_SUBST([HAVE_SIGACTION])
+  HAVE_STRUCT_SIGACTION_SA_SIGACTION=1;
+                               AC_SUBST([HAVE_STRUCT_SIGACTION_SA_SIGACTION])
 ])

--- a/modules/signal
+++ b/modules/signal
@@ -28,6 +28,7 @@
 	      -e 's|@''HAVE_SIGSET_T''@|$(HAVE_SIGSET_T)|g' \
 	      -e 's|@''HAVE_SIGINFO_T''@|$(HAVE_SIGINFO_T)|g' \
 	      -e 's|@''HAVE_SIGACTION''@|$(HAVE_SIGACTION)|g' \
+	      -e 's|@''HAVE_STRUCT_SIGACTION_SA_SIGACTION''@|$(HAVE_STRUCT_SIGACTION_SA_SIGACTION)|g' \
 	      -e '/definition of GL_LINK_WARNING/r $(LINK_WARNING_H)' \
 	      < $(srcdir)/signal.in.h; \
 	} > $@-t