--- zip30/unix/configure.old	2022-09-08 10:48:41.374211517 -0400
+++ zip30/unix/configure	2022-09-08 10:55:09.859229607 -0400
@@ -507,18 +507,18 @@ $CC $CFLAGS -c conftest.c >/dev/null 2>/
 # add NO_'function_name' to flags if missing
 
 for func in rmdir strchr strrchr rename mktemp mktime mkstemp
 do
   echo Check for $func
-  echo "int main(){ $func(); return 0; }" > conftest.c
+  echo "char $func(); int main(){ return $func(); }" > conftest.c
   $CC $BFLAG -o conftest conftest.c >/dev/null 2>/dev/null
   [ $? -ne 0 ] && CFLAGS="${CFLAGS} -DNO_`echo $func | tr '[a-z]' '[A-Z]'`"
 done
 
 
 echo Check for memset
-echo "int main(){ char k; memset(&k,0,0); return 0; }" > conftest.c
+echo "int main(){ char memset(); return memset(); }" > conftest.c
 $CC -o conftest conftest.c >/dev/null 2>/dev/null
 [ $? -ne 0 ] && CFLAGS="${CFLAGS} -DZMEM"
 
 
 echo Check for memmove
@@ -551,11 +551,11 @@ $CC $CFLAGS -c conftest.c >/dev/null 2>/
 [ $? -ne 0 ] && CFLAGS="${CFLAGS} -DNO_ERRNO"
 
 
 echo Check for directory libraries
 cat > conftest.c << _EOF_
-int main() { return closedir(opendir(".")); }
+int main() { char closedir(); char opendir(); return closedir(opendir()); }
 _EOF_
 
 $CC -o conftest conftest.c >/dev/null 2>/dev/null
 if [ $? -ne 0 ]; then
   OPT=""
@@ -573,11 +573,11 @@ fi
 
 
 # Dynix/ptx 1.3 needed this
 
 echo Check for readlink
-echo "int main(){ return readlink(); }" > conftest.c
+echo "int main(){ char readlink(); return readlink(); }" > conftest.c
 $CC -o conftest conftest.c >/dev/null 2>/dev/null
 if [ $? -ne 0 ]; then
   $CC -o conftest conftest.c -lseq >/dev/null 2>/dev/null
   [ $? -eq 0 ] && LFLAGS2="${LFLAGS2} -lseq"
 fi