avr_register_io_[read,write](): fail if overriding earlier registration.

[simavr] / simavr / sim / sim_io.c

diff --git a/simavr/sim/sim_io.c b/simavr/sim/sim_io.c
index 42e8c1b..3ef9d35 100644 (file)
--- a/simavr/sim/sim_io.c
+++ b/simavr/sim/sim_io.c
@@ -47,6 +47,10 @@ void avr_register_io(avr_t *avr, avr_io_t * io)
 void avr_register_io_read(avr_t *avr, avr_io_addr_t addr, avr_io_read_t readp, void * param)
 {
        avr_io_addr_t a = AVR_DATA_TO_IO(addr);
+       if (avr->io[a].r.param || avr->io[a].r.c) {
+               fputs("Error: avr_register_io_read(): Already registered, refusing to override.\n", stderr);
+               exit(1);
+       }
        avr->io[a].r.param = param;
        avr->io[a].r.c = readp;
 }
@@ -54,6 +58,10 @@ void avr_register_io_read(avr_t *avr, avr_io_addr_t addr, avr_io_read_t readp, v
 void avr_register_io_write(avr_t *avr, avr_io_addr_t addr, avr_io_write_t writep, void * param)
 {
        avr_io_addr_t a = AVR_DATA_TO_IO(addr);
+       if (avr->io[a].w.param || avr->io[a].w.c) {
+               fputs("Error: avr_register_io_write(): Already registered, refusing to override.\n", stderr);
+               exit(1);
+       }
        avr->io[a].w.param = param;
        avr->io[a].w.c = writep;
 }