ChangeLog:

- big commit.

libc/conio/conio.c

@@ -356,6 +356,11 @@ char cputs(const char *s) __naked
         or    a, l
         ret   z
 
+        ;; IX is callee-saved under SDCC's z80 ABI. We use it as a
+        ;; function pointer below (ld ix, #__raw_putch_raw0/1) so save
+        ;; the caller's value up front and restore before every ret.
+        push  ix
+
         ;; KEEP_EXIST_ATTR? high byte of g_text_attr != 0
         ld    a, (_g_text_attr + 1)
         or    a, a
@@ -398,11 +403,13 @@ char cputs(const char *s) __naked
     _cputs_loop_end:
 
         call  __set_cursor
+        pop   ix                        ; restore caller's IX
         xor   a, a                      ; return 0
         ret
 
     _cputs_fast:
         call  __cputs_pchars
+        pop   ix                        ; restore caller's IX
         xor   a, a                      ; return 0
         ret
     __endasm;