The change from #2495 didn't take into account that recursive calls to main()

are legal in C. With the changes from #2495, such calls will usually crash the
machine. But recursive calls to main() are rare and on the 6502 every byte
saved is precious. So this change limits the effect of #2495 to cc65 mode and
at the same time disallows recursive calls to main() in this mode. If
recursive calls to main() are actually required, the code must be compiled in
c89 or c99 mode.

doc/cc65.sgml

@@ -823,6 +823,11 @@ and the one defined by the ISO standard:
         as it sounds, since the 6502 has so few registers that it isn't
         possible to keep values in registers anyway.
         <p>
+<item>  In <tt/cc65/ mode, <tt/main()/ cannot be called recursively. If this
+        is necessary, the program must be compiled in <tt/c89/ or <tt/c99/ mode
+        using the <tt><ref id="option--standard" name="--standard"></tt>
+        command line option.
+        <p>
 </itemize>
 
 There may be some more minor differences I'm currently not aware of. The