https://bugs.gentoo.org/show_bug.cgi?id=251745
https://sourceforge.net/tracker/index.php?func=detail&aid=2520894&group_id=5982&atid=105982

--- a/libwsmake/wsSubTag.cpp
+++ b/libwsmake/wsSubTag.cpp
@@ -22,6 +22,7 @@
  ***********************************************************************/
 #include <cstdio>
 #include <cstring>
+#include <cstdlib>
 
 #include <unistd.h>
 #ifdef HAVE_SYS_WAIT_H
--- a/libwsmake/wsWebPage.cpp
+++ b/libwsmake/wsWebPage.cpp
@@ -23,6 +23,7 @@
 #include <cassert>
 #include <cerrno>
 #include <ctime>
+#include <cstdlib>
 
 #include "wsmake.h"
 
--- a/libwsmake/wsUtil.cpp
+++ b/libwsmake/wsUtil.cpp
@@ -28,6 +28,7 @@
 #include <cassert>
 #include <cerrno>
 #include <cstring>
+#include <cstdlib>
 
 #ifdef HAVE_UTIME_H
 #include <utime.h>