ucontext.h check requires signal.h.

configure

@@ -11541,7 +11541,6 @@ done
 
 
 
-
 for ac_header in \
 	arpa/inet.h \
 	arpa/nameser.h \
@@ -11608,7 +11607,6 @@ for ac_header in \
 	sys/wait.h \
 	syscall.h \
 	termios.h \
-	ucontext.h \
 	unistd.h \
 	utime.h \
 
@@ -11990,6 +11988,54 @@ done
 
 
 
+for ac_header in ucontext.h
+do
+as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  cat >conftest.$ac_ext <<_ACEOF
+#line $LINENO "configure"
+#include "confdefs.h"
+#include <signal.h>
+
+#include <$ac_header>
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+         { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  eval "$as_ac_Header=yes"
+else
+  echo "$as_me: failed program was:" >&5
+cat conftest.$ac_ext >&5
+eval "$as_ac_Header=no"
+fi
+rm -f conftest.$ac_objext conftest.$ac_ext
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+if test `eval echo '${'$as_ac_Header'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_header" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+
+done
+
+
+
 echo "$as_me:$LINENO: checking for an ANSI C-conforming const" >&5
 echo $ECHO_N "checking for an ANSI C-conforming const... $ECHO_C" >&6
 if test "${ac_cv_c_const+set}" = set; then

configure.ac

@@ -1022,7 +1022,6 @@ AC_CHECK_HEADERS(\
 	sys/wait.h \
 	syscall.h \
 	termios.h \
-	ucontext.h \
 	unistd.h \
 	utime.h \
 )
@@ -1057,6 +1056,8 @@ AC_CHECK_HEADERS(resolv.h,,,
      # include <sys/socket.h>
      #endif])
 
+AC_CHECK_HEADERS(ucontext.h,,,[#include <signal.h>])
+
 dnl **** Check for types ****
 
 AC_C_CONST