%expect-rr: fix the computation of the overall number of conflicts

On a grammar such as

   exp: "num" | "num" | "num"

we currently report only one RR conflict, instead of two.

This bug is present since the origins of Bison

    commit 08089d5d35
    Author: David MacKenzie <djm@djmnet.org>
    Date:   Tue Apr 20 05:42:52 1993 +0000

       Initial revision

and was preserved in

    commit 676385e29c
    Author: Paul Hilfinger <Hilfinger@CS.Berkeley.EDU>
    Date:   Fri Jun 28 02:26:44 2002 +0000

       Initial check-in introducing experimental GLR parsing.  See entry in
       ChangeLog dated 2002-06-27 from Paul Hilfinger for details.

See
https://lists.gnu.org/archive/html/bison-patches/2018-11/msg00011.html

* src/conflicts.h, src/conflicts.c (count_state_rr_conflicts)
(count_rr_conflicts): Use only the correct count of conflicts.
* tests/glr-regression.at: Fix expectations.

NEWS

@@ -26,6 +26,20 @@ GNU Bison NEWS
   The use of the %error-verbose directive is deprecated in favor of "%define
   parse.error verbose" since Bison 3.0, but no warning was issued.
 
+** Bug fixes
+
+*** Incorrect number of reduce-reduce conflicts
+
+  On a grammar such as
+
+     exp: "num" | "num" | "num"
+
+  bison used report a single RR conflict, instead of two.  This is now
+  fixed.  This was the oldest (known) bug in Bison: it was there when Bison
+  was entered in the RCS version control system, in December 1987.
+
+  Some grammar files might have to adjust their %expect-rr.
+
 * Noteworthy changes in release 3.2.2 (2018-11-21) [stable]
 
 ** Bug fixes

src/conflicts.c

@@ -467,15 +467,13 @@ count_sr_conflicts (void)
 
 
 
-/*----------------------------------------------------------------.
+/*-----------------------------------------------------------------.
-| Count the number of reduce/reduce conflicts.  If ONE_PER_TOKEN, |
+| Count the number of reduce/reduce conflicts.  Count one conflict |
-| count one conflict for each token that has any reduce/reduce    |
+| for each reduction after the first for a given token.            |
-| conflicts.  Otherwise, count one conflict for each reduction    |
+`-----------------------------------------------------------------*/
-| after the first for a given token.                              |
-`----------------------------------------------------------------*/
 
 static size_t
-count_state_rr_conflicts (state *s, bool one_per_token)
+count_state_rr_conflicts (state *s)
 {
   reductions *reds = s->reductions;
   size_t res = 0;
@@ -486,20 +484,20 @@ count_state_rr_conflicts (state *s, bool one_per_token)
       for (int j = 0; j < reds->num; ++j)
         count += bitset_test (reds->lookahead_tokens[j], i);
       if (count >= 2)
-        res += one_per_token ? 1 : count-1;
+        res += count-1;
     }
 
   return res;
 }
 
 static size_t
-count_rr_conflicts (bool one_per_token)
+count_rr_conflicts (void)
 {
   size_t res = 0;
   /* Conflicts by state.  */
   for (state_number i = 0; i < nstates; ++i)
     if (conflicts[i])
-      res += count_state_rr_conflicts (states[i], one_per_token);
+      res += count_state_rr_conflicts (states[i]);
   return res;
 }
 
@@ -591,7 +589,7 @@ conflicts_output (FILE *out)
       if (conflicts[i])
         {
           int src = count_state_sr_conflicts (s);
-          int rrc = count_state_rr_conflicts (s, true);
+          int rrc = count_state_rr_conflicts (s);
           fprintf (out, _("State %d "), i);
           if (src && rrc)
             fprintf (out,
@@ -608,17 +606,14 @@ conflicts_output (FILE *out)
     fputs ("\n\n", out);
 }
 
-/*--------------------------------------------------------.
+/*--------------------------------------------.
-| Total the number of S/R and R/R conflicts.  Unlike the  |
+| Total the number of S/R and R/R conflicts.  |
-| code in conflicts_output, however, count EACH pair of   |
+`--------------------------------------------*/
-| reductions for the same state and lookahead as one      |
-| conflict.                                               |
-`--------------------------------------------------------*/
 
 int
 conflicts_total_count (void)
 {
-  return count_sr_conflicts () + count_rr_conflicts (false);
+  return count_sr_conflicts () + count_rr_conflicts ();
 }
 
 /*------------------------------.
@@ -692,7 +687,7 @@ conflicts_print (void)
   }
 
   {
-    int total = count_rr_conflicts (true);
+    int total = count_rr_conflicts ();
     /* If %expect-rr is not used, but %expect is, then expect 0 rr.  */
     int expected =
       (expected_rr_conflicts == -1 && expected_sr_conflicts != -1)

src/conflicts.h

@@ -44,4 +44,5 @@ void conflicts_free (void);
 /* Were there conflicts? */
 extern int expected_sr_conflicts;
 extern int expected_rr_conflicts;
+
 #endif /* !CONFLICTS_H_ */

tests/glr-regression.at

@@ -342,7 +342,7 @@ AT_BISON_OPTION_POPDEFS
 
 AT_BISON_CHECK([[-o glr-regr3.c -rall glr-regr3.y]], 0, [],
 [[glr-regr3.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
-glr-regr3.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
+glr-regr3.y: warning: 2 reduce/reduce conflicts [-Wconflicts-rr]
 ]])
 AT_COMPILE([glr-regr3])
 
@@ -437,7 +437,7 @@ merge (YYSTYPE s1, YYSTYPE s2)
 AT_BISON_OPTION_POPDEFS
 
 AT_BISON_CHECK([[-o glr-regr4.c -rall glr-regr4.y]], 0, [],
-[[glr-regr4.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
+[[glr-regr4.y: warning: 2 reduce/reduce conflicts [-Wconflicts-rr]
 ]])
 AT_COMPILE([glr-regr4])
 
@@ -799,7 +799,7 @@ main (void)
 AT_BISON_OPTION_POPDEFS
 
 AT_BISON_CHECK([[-o glr-regr9.c -rall glr-regr9.y]], 0, [],
-[[glr-regr9.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
+[[glr-regr9.y: warning: 2 reduce/reduce conflicts [-Wconflicts-rr]
 ]])
 AT_COMPILE([glr-regr9])
 
@@ -1363,7 +1363,7 @@ main (void)
 AT_BISON_OPTION_POPDEFS
 
 AT_BISON_CHECK([[-o glr-regr14.c -rall glr-regr14.y]], 0, [],
-[[glr-regr14.y: warning: 3 reduce/reduce conflicts [-Wconflicts-rr]
+[[glr-regr14.y: warning: 5 reduce/reduce conflicts [-Wconflicts-rr]
 ]])
 AT_COMPILE([glr-regr14])