diff: svar.m changes

[Fergus Henderson]

clpr/svar.m:
	Restore `stamp' after a commit.  This is necessary to ensure that
	`stamp' stays in sync with MR_ticket_counter, so that the test
	`stamp != MR_current_choicepoint_id()' remains valid.

	Check for doing a commit when `nlin_count' is non-zero,
	and if so, issue a warning.  (Any such commit is potentially
	unsound, and might lead to wrong answers.)

	Also add a couple of comments.

Index: svar.m
===================================================================
RCS file: /home/staff/zs/imp/clpr/svar.m,v
retrieving revision 1.5
diff -u -u -r1.5 svar.m
--- 1.5	1997/08/24 10:33:01
+++ svar.m	1997/08/25 17:38:53
@@ -306,7 +306,7 @@
 /*
 ** There are three trails:
 **	- the Mercury trail
-**	- the svar.m trail
+**	- the svar.m trail-info free list
 **	- the CLP(R) trail
 ** The Mercury trail contains function trail entries which point to
 ** the svar.m trail.  (The reason why those two are separate is modularity.)
@@ -314,6 +314,7 @@
 ** The svar.m trail entries store the CLP(R) global variables, including
 ** the `trtop' variable, which points to the top of the CLP(R) trail.
 */
+/* XXX rename as `choicepoint' */
 typedef struct ML_svar_trail_entry {
 	int stamp;
 	int slack_id;
@@ -326,9 +327,12 @@
 ML_svar_trail_entry ML_svar_first_trail_entry;
 ML_svar_trail_entry * ML_svar_trail_ptr = &ML_svar_first_trail_entry;
 
+/* XXX efficiency could be improved -- we should use a free list here */
+
 #define ML_svar_next_trail_entry()					\
 	( ML_svar_trail_ptr->next == NULL ?				\
 		(ML_svar_trail_ptr->next = make(ML_svar_trail_entry),	\
+		ML_svar_trail_ptr->next->next = NULL,			\
 		ML_svar_trail_ptr->next->prev = ML_svar_trail_ptr,	\
 		ML_svar_trail_ptr = ML_svar_trail_ptr->next)		\
 	:								\
@@ -339,7 +343,7 @@
 		
 #define ML_svar_maybe_trail_solver()				\
 	do {							\
-		if(stamp != MR_current_choicepoint_id()) {	\
+		if (stamp != MR_current_choicepoint_id()) {	\
 			save_transient_registers();		\
 			ML_svar_trail_solver();			\
 			restore_transient_registers();		\
@@ -381,10 +385,16 @@
 			trtop = old_trtop;
 			break;
 		}
-		case MR_gc:
 		case MR_commit:
+			stamp = trail_entry->stamp;
+			if (nlin_count != 0) {
+				fprintf(stderr, ""svar.m: warning: ""
+					""non-linear goals delayed, ""
+					""but committing anyway\n"");
+			}
+			break;
 		default:
-			/* do nothing */ ;
+			fatal_error(""svar.m: unknown MR_untrail_reason"");
 	}
 	ML_svar_prev_trail_entry();
 }
@@ -469,7 +479,7 @@
 /*
 INIT init_svar_module
 */
-void init_svar_module(void) __attribute__((constructor)); /* XXX */
+void init_svar_module(void) __attribute__((constructor)); /* XXX gcc-ism */
 void init_svar_module(void) {
 	extern ModuleFunc svar_module;
 	svar_module();

-- 
Fergus Henderson <fjh at cs.mu.oz.au>   |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3         |     -- the last words of T. S. Garp.