From 399f329936d9b11f48257f0f6aa323d65ccc6aaf Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Sun, 22 Jun 2014 15:18:32 +1000
Subject: [PATCH] parsergen: improve tracing.

1/ perform the "is null?" test on trace find in parser_trace.
   code is cleaner that way

2/ Report the action at each step in the parse.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 csrc/parsergen.mdc | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/csrc/parsergen.mdc b/csrc/parsergen.mdc
index 19703bc..9306592 100644
--- a/csrc/parsergen.mdc
+++ b/csrc/parsergen.mdc
@@ -2601,14 +2601,14 @@ since the last state which could have been at the start of a line.
 			if (!tk)
 				tk = tok_copy(token_next(tokens));
 			next.sym = tk->num;
-			if (trace)
-				parser_trace(trace, &p, &next, tk, states, non_term, config->known_count);
+			parser_trace(trace, &p, &next, tk, states, non_term, config->known_count);
 
 			if (next.sym == TK_in) {
 				next.starts_indented = 1;
 				next.indents = 1;
 				free(tk);
 				tk = NULL;
+				parser_trace_action(trace, "Record");
 				continue;
 			}
 			if (next.sym == TK_out) {
@@ -2625,6 +2625,7 @@ since the last state which could have been at the start of a line.
 					}
 					free(tk);
 					tk = NULL;
+					parser_trace_action(trace, "Cancel");
 					continue;
 				}
 				// fall through and force a REDUCE (as 'shift'
@@ -2634,6 +2635,7 @@ since the last state which could have been at the start of a line.
 				if (! tos->newline_permitted) {
 					free(tk);
 					tk = NULL;
+					parser_trace_action(trace, "Discard");
 					continue;
 				}
 			}
@@ -2641,6 +2643,7 @@ since the last state which could have been at the start of a line.
 				tk = NULL;
 				next.starts_indented = 0;
 				next.indents = 0;
+				parser_trace_action(trace, "Shift");
 				continue;
 			}
 			if (states[tos->state].reduce_prod >= 0) {
@@ -2673,6 +2676,7 @@ since the last state which could have been at the start of a line.
 					accepted = 1;
 					ret = res;
 				}
+				parser_trace_action(trace, "Reduce");
 				continue;
 			}
 			if (tk->num == TK_out) {
@@ -2683,6 +2687,7 @@ since the last state which could have been at the start of a line.
 				frame.sym = states[tos->state].shift_sym;
 				shift(&p, &frame, tok_copy(*tk), states);
 				// FIXME need to report this error somehow
+				parser_trace_action(trace, "Synthesize");
 				continue;
 			}
 			/* Error. We walk up the stack until we
@@ -2692,6 +2697,7 @@ since the last state which could have been at the start of a line.
 			 * Then we discard input tokens until
 			 * we find one that is acceptable.
 			 */
+			parser_trace_action(trace, "ERROR");
 
 			err_tk = tok_copy(*tk);
 			next.sym = TK_error;
@@ -2777,6 +2783,8 @@ end inside square brackets.
 			  const char *non_term[], int knowns)
 	{
 		int i;
+		if (!trace)
+			return;
 		for (i = 0; i < p->tos; i++) {
 			struct frame *f = &p->stack[i];
 			if (i) {
@@ -2806,7 +2814,13 @@ end inside square brackets.
 		if (n->indents)
 			fprintf(trace, "%c%d", n->starts_indented?':':'.',
 				n->indents);
-		fputs("]\n", trace);
+		fputs("]", trace);
+	}
+
+	void parser_trace_action(FILE *trace, char *action)
+	{
+		if (trace)
+			fprintf(trace, " - %s\n", action);
 	}
 
 # A Worked Example
-- 
2.43.0