oksh-noxz [fork] Portable OpenBSD ksh, based on the Public Domain Korn Shell (pdksh).
	git clone https://noxz.tech/git/oksh-noxz.git
	oksh-noxz

commit: 62f501f0b29cd88ed4fd4ed6d252dcd62a42b954
parent: 34dc34c156d68e59255fa37b8d2b29f6091a474d
author: Brian Callahan <bcallah@openbsd.org>
date:   Tue, 16 Jan 2018 23:16:58 -0500

Last commit added a function declared __dead which is a synonym for __attribute__((__no_return__)).
Check for it in configure as well as the FreeBSD synonym __dead2.
Fall back to __attribute__((__no_return__)) if you don't have either.

diff --git a/configure b/configure
@@ -51,6 +51,36 @@ EOF
   fi
 }
 
+deadcheck() {
+  cat << EOF > conftest.c
+#include <stdlib.h>
+__dead usage(void){exit(1);}int main(void){usage();return 0;}
+EOF
+  $cc $tflags -o conftest conftest.c > /dev/null 2>&1
+  if [ $? -eq 0 ] ; then
+    rm -f conftest conftest.c
+    return 0
+  else
+    rm -f conftest conftest.c
+    return 1
+  fi
+}
+
+dead2check() {
+  cat << EOF > conftest.c
+#include <stdlib.h>
+__dead2 usage(void){exit(1);}int main(void){usage();return 0;}
+EOF
+  $cc $tflags -o conftest conftest.c > /dev/null 2>&1
+  if [ $? -eq 0 ] ; then
+    rm -f conftest conftest.c
+    return 0
+  else
+    rm -f conftest conftest.c
+    return 1
+  fi
+}
+
 pledgecheck() {
   cat << EOF > conftest.c
 #include <unistd.h>
@@ -332,6 +362,23 @@ cat << EOF > pconfig.h
 
 EOF
 
+printf "checking for __dead... "
+deadcheck
+if [ $? -eq 0 ] ; then
+  echo "yes"
+else
+  echo "no"
+  printf "checking for __dead2... "
+  dead2check
+  if [ $? -eq 0 ] ; then
+    echo "#define __dead __dead2" >> pconfig.h
+    echo "yes"
+  else
+    echo "#define __dead __attribute__((__no_return__))" >> pconfig.h
+    echo "no"
+  fi
+fi
+
 printf "checking for confstr... "
 confstrcheck
 if [ $? -eq 0 ] ; then