Hi, The attached patch fixes this issue for me. I tried finding the right combination of _???_SOURCE defines to avoid having to do this, but was unsuccessful.
-- Matt Kraai https://ftbfs.org/kraai
diff -ru xtrs-4.9c~/debug.c xtrs-4.9c/debug.c --- xtrs-4.9c~/debug.c 2011-12-04 02:52:24.000000000 +0000 +++ xtrs-4.9c/debug.c 2011-12-04 02:52:38.000000000 +0000 @@ -18,14 +18,14 @@ Last modified on Tue May 1 17:52:20 PDT 2001 by mann */ -#include "z80.h" -#include "trs.h" - #include <stdlib.h> #include <signal.h> #include <errno.h> #include <string.h> +#include "z80.h" +#include "trs.h" + #ifdef READLINE #include <readline/readline.h> #include <readline/history.h> diff -ru xtrs-4.9c~/z80.h xtrs-4.9c/z80.h --- xtrs-4.9c~/z80.h 2011-12-04 02:52:24.000000000 +0000 +++ xtrs-4.9c/z80.h 2011-12-04 02:53:38.000000000 +0000 @@ -149,6 +149,7 @@ #define REG_IY_LOW (z80_state.iy.byte.low) #define REG_SP (z80_state.sp.word) +#undef REG_PC #define REG_PC (z80_state.pc.word) #define REG_AF (z80_state.af.word)