"hardware" (haha) watch points (one!) in progs. only catches changes done by progs, and the expression parser is as flaky as anything, but it's better than nothing :)

include/QF/progs.h

@@ -1283,6 +1283,7 @@ void *PR_Zone_Realloc (progs_t *pr, void *ptr, pr_int_t size);
 void PR_Debug_Init (void);
 void PR_Debug_Init_Cvars (void);
 int PR_LoadDebug (progs_t *pr);
+void PR_Debug_Watch (progs_t *pr, const char *expr);
 pr_auxfunction_t *PR_Get_Lineno_Func (progs_t *pr, pr_lineno_t *lineno);
 pr_uint_t PR_Get_Lineno_Addr (progs_t *pr, pr_lineno_t *lineno);
 pr_uint_t PR_Get_Lineno_Line (progs_t *pr, pr_lineno_t *lineno);
@@ -1452,6 +1453,7 @@ struct progs_s {
 	struct pr_auxfunction_s **auxfunction_map;
 	struct pr_lineno_s *linenos;
 	ddef_t     *local_defs;
+	pr_type_t  *watch;
 	//@}
 
 	/// required globals (for OP_STATE)

libs/gamecode/engine/pr_debug.c

@@ -41,7 +41,7 @@ static __attribute__ ((used)) const char rcsid[] =
 # include <strings.h>
 #endif
 #include <ctype.h>
-
+#include <sys/types.h>
 #include <stdlib.h>
 
 #include "QF/cvar.h"
@@ -51,6 +51,7 @@ static __attribute__ ((used)) const char rcsid[] =
 #include "QF/progs.h"
 #include "QF/qendian.h"
 #include "QF/quakefs.h"
+#include "QF/script.h"
 #include "QF/sys.h"
 #include "QF/va.h"
 #include "QF/zone.h"
@@ -119,6 +120,68 @@ source_path_f (cvar_t *var)
 	source_paths[i] = 0;
 }
 
+static void
+pr_debug_watch_error (script_t *script, const char *msg)
+{
+	Sys_Printf ("%s\n", msg);
+}
+
+VISIBLE void
+PR_Debug_Watch (progs_t *pr, const char *expr)
+{
+	script_t   *ws;
+	char       *e;
+
+	if (!expr) {
+		Sys_Printf ("watch <watchpoint expr>\n");
+		if (pr->watch) {
+			Sys_Printf ("    watching [%d]\n",
+						(int) (intptr_t) (pr->watch - pr->pr_globals));
+		} else {
+			Sys_Printf ("    none active\n");
+		}
+		return;
+	}
+	ws = Script_New ();
+	ws->error = pr_debug_watch_error;
+	Script_Start (ws, "<console>", expr);
+	pr->watch = 0;
+	if (Script_GetToken (ws, 1)) {
+		if (strequal (ws->token->str, "[")) {
+			edict_t    *ent;
+			ddef_t     *field;
+
+			if (!Script_GetToken (ws, 1))
+				goto error;
+			ent = EDICT_NUM (pr, strtol (ws->token->str, &e, 0));
+			if (e == ws->token->str)
+				goto error;
+			if (!Script_GetToken (ws, 1) && !strequal (ws->token->str, "]" ))
+				goto error;
+			if (!Script_GetToken (ws, 1) && !strequal (ws->token->str, "." ))
+				goto error;
+			if (!Script_GetToken (ws, 1))
+				goto error;
+			field = PR_FindField (pr, ws->token->str);
+			if (!field)
+				goto error;
+			if (Script_TokenAvailable (ws, 1))
+				Sys_Printf ("ignoring tail\n");
+			pr->watch = &ent->v[field->ofs];
+		} else {
+			ddef_t     *global = PR_FindGlobal (pr, ws->token->str);
+			if (!global)
+				goto error;
+			pr->watch = PR_GetPointer (pr, global->ofs);
+		}
+	}
+error:
+	if (pr->watch)
+		Sys_Printf ("watchpoint set to [%d]\n", PR_SetPointer (pr, pr->watch));
+	else
+		Sys_Printf ("watchpoint cleared\n");
+}
+
 void
 PR_Debug_Init (void)
 {

libs/gamecode/engine/pr_exec.c

@@ -307,6 +307,7 @@ PR_ExecuteProgram (progs_t * pr, func_t fnum)
 	dstatement_t *st;
 	edict_t    *ed;
 	pr_type_t  *ptr;
+	pr_type_t   old_val, *watch = 0;
 
 	// make a stack frame
 	exitdepth = pr->pr_depth;
@@ -321,6 +322,11 @@ PR_ExecuteProgram (progs_t * pr, func_t fnum)
 	}
 	st = pr->pr_statements + pr->pr_xstatement;
 
+	if (pr->watch) {
+		watch = pr->watch;
+		old_val = *watch;
+	}
+
 	while (1) {
 		pr_type_t  *op_a, *op_b, *op_c;
 
@@ -1014,5 +1020,8 @@ op_call:
 			default:
 				PR_RunError (pr, "Bad opcode %i", st->op);
 		}
+		if (watch && watch->integer_var != old_val.integer_var)
+			PR_RunError (pr, "watchpoint hit: %d -> %d", old_val.integer_var,
+						 watch->integer_var);
 	}
 }

qw/source/sv_progs.c

@@ -157,6 +157,12 @@ PR_Profile_f (void)
 	PR_Profile (&sv_pr_state);
 }
 
+static void
+watch_f (void)
+{
+	PR_Debug_Watch (&sv_pr_state, Cmd_Argc () < 2 ? 0 : Cmd_Args (1));
+}
+
 static int
 parse_field (progs_t *pr, const char *key, const char *value)
 {
@@ -528,6 +534,7 @@ SV_Progs_Init (void)
 					"Display summary information on the edicts in the game.");
 	Cmd_AddCommand ("profile", PR_Profile_f, "FIXME: Report information about "
 					"QuakeC Stuff (\?\?\?) No Description");
+	Cmd_AddCommand ("watch", watch_f, "set watchpoint");
 }
 
 void