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: db2df189e3315545ef0f9dceb07dbdc2aae8515e
parent: 668c326d5d10bc574eff91fbaadac6cb7f10d416
author: Brian Callahan <bcallah@openbsd.org>
date:   Sun, 3 Jan 2021 03:48:50 -0500

We weren't actually checking the case where you don't use -std=c99.
We are now! Should be a no-op on all modern-ish clang and gcc.

diff --git a/configure b/configure
@@ -390,6 +390,22 @@ EOF
   fi
 }
 
+noc99check() {
+  cat << EOF > conftest.c
+#include <stdio.h>
+int main(void){long long l;for (int i=0;i<1;i++)printf("%s",__func__);return 0;}
+EOF
+  $cc $cflags -o conftest.o -c conftest.c > /dev/null 2>&1
+  $cc $ldflags -o conftest conftest.o > /dev/null 2>&1
+  if [ $? -eq 0 ] ; then
+    rm -f conftest conftest.o conftest.c
+    return 0
+  else
+    rm -f conftest conftest.o conftest.c
+    return 1
+  fi
+}
+
 noreturncheck() {
   cat << EOF > conftest.c
 #include <stdlib.h>
@@ -896,7 +912,7 @@ else
 fi
 
 printf "checking if C compiler can compile C99 without -std=c99... "
-c99check
+noc99check
 if [ $? -ne 0 ] ; then
   echo "no"
   printf "checking if C compiler can compile C99 with -std=c99... "