Include <stdlib.h> for the exit function.
Submitted upstream: <https://sourceforge.net/p/sing/bugs/7/>
diff --git a/help.c b/help.c
index f11150a54245c048..67bd1ff115c31aae 100644
--- a/help.c
+++ b/help.c
@@ -13,6 +13,10 @@ static const char rcsid[] =
#include <stdio.h>
+#ifdef STDC_HEADERS
+#include <stdlib.h>
+#endif
+
void
help(void)
{