FYI: fix bugs when user action cuts nondeterministic parse

[Joel E. Denny]

2006-01-05  Joel E. Denny  <address@hidden>

        * data/glr.c (yyresolveValue): When merging semantic options, if at
        least one user action succeeds but a later one cuts the parse, then
        destroy the semantic value before returning rather than leaking it.
        (yyresolveStates): If a user action cuts the parse and thus
        yyresolveValue fails, ignore the (unset) semantic value rather than
        corrupting the yyGLRState, and empty the semantic options list since
        the user actions should have called all necessary destructors.
        Simplify code with YYCHK.
        * tests/glr-regression.at (Corrupted semantic options if user action
        cuts parse): New test case.
        (Undesirable destructors if user action cuts parse): New test case.
        Before applying any of this patch, this test case never actually failed
        for me... but only because the corrupted semantic options usually
        masked this bug.
        (Leaked merged semantic value if user action cuts parse): New test
        case.

Index: data/glr.c
===================================================================
RCS file: /sources/bison/bison/data/glr.c,v
retrieving revision 1.153
diff -p -u -r1.153 glr.c
--- data/glr.c  3 Jan 2006 20:25:54 -0000       1.153
+++ data/glr.c  5 Jan 2006 20:34:14 -0000
@@ -1612,7 +1612,7 @@ yypreference (yySemanticOption* y0, yySe
   return 0;
 }
 
-static YYRESULTTAG yyresolveValue (yySemanticOption* yyoptionList,
+static YYRESULTTAG yyresolveValue (yyGLRState* yys,
                                   yyGLRStack* yystackp, YYSTYPE* yyvalp,
                                   YYLTYPE* yylocp]b4_user_formals[);
 
@@ -1620,20 +1620,21 @@ static YYRESULTTAG
 yyresolveStates (yyGLRState* yys, int yyn,
                 yyGLRStack* yystackp]b4_user_formals[)
 {
-  YYRESULTTAG yyflag;
   if (0 < yyn)
     {
       YYASSERT (yys->yypred);
-      yyflag = yyresolveStates (yys->yypred, yyn-1, yystackp]b4_user_args[);
-      if (yyflag != yyok)
-       return yyflag;
+      YYCHK (yyresolveStates (yys->yypred, yyn-1, yystackp]b4_user_args[));
       if (! yys->yyresolved)
        {
-         yyflag = yyresolveValue (yys->yysemantics.yyfirstVal, yystackp,
-                                  &yys->yysemantics.yysval, &yys->yyloc
-                                 ]b4_user_args[);
+         YYSTYPE yysval;
+         YYRESULTTAG yyflag = yyresolveValue (yys, yystackp, &yysval,
+                                              &yys->yyloc]b4_user_args[);
          if (yyflag != yyok)
-           return yyflag;
+           {
+             yys->yysemantics.yyfirstVal = NULL;
+             return yyflag;
+           }
+         yys->yysemantics.yysval = yysval;
          yys->yyresolved = yytrue;
        }
     }
@@ -1728,12 +1729,13 @@ yyreportAmbiguity (yySemanticOption* yyx
 }
 
 
-/** Resolve the ambiguity represented by OPTIONLIST, perform the indicated
+/** Resolve the ambiguity represented in state S, perform the indicated
  *  actions, and return the result.  */
 static YYRESULTTAG
-yyresolveValue (yySemanticOption* yyoptionList, yyGLRStack* yystackp,
-               YYSTYPE* yyvalp, YYLTYPE* yylocp]b4_user_formals[)
+yyresolveValue (yyGLRState* yys, yyGLRStack* yystackp, YYSTYPE* yyvalp,
+               YYLTYPE* yylocp]b4_user_formals[)
 {
+  yySemanticOption* yyoptionList = yys->yysemantics.yyfirstVal;
   yySemanticOption* yybest;
   yySemanticOption** yypp;
   yybool yymerge;
@@ -1786,8 +1788,15 @@ yyresolveValue (yySemanticOption* yyopti
            {
              YYSTYPE yyval1;
              YYLTYPE yydummy;
-             YYCHK (yyresolveAction (yyp, yystackp, &yyval1,
-                                     &yydummy]b4_user_args[));
+             YYRESULTTAG yyflag = yyresolveAction (yyp, yystackp, &yyval1,
+                                                   &yydummy]b4_user_args[);
+             if (yyflag != yyok)
+               {
+                 yydestruct ("Cleanup: discarding merged value",
+                             yystos[yys->yylrState],
+                             yyvalp]b4_location_if([, yylocp])[]b4_user_args[);
+                 return yyflag;
+               }
              yyuserMerge (yymerger[yyp->yyrule], yyvalp, &yyval1);
            }
        }
Index: tests/glr-regression.at
===================================================================
RCS file: /sources/bison/bison/tests/glr-regression.at,v
retrieving revision 1.22
diff -p -u -r1.22 glr-regression.at
--- tests/glr-regression.at     22 Dec 2005 11:40:05 -0000      1.22
+++ tests/glr-regression.at     5 Jan 2006 20:34:14 -0000
@@ -815,3 +815,203 @@ AT_CHECK([[./glr-regr9]], 0, [],
 ])
 
 AT_CLEANUP
+
+
+## ------------------------------------------------------------------------- ##
+## Corrupted semantic options if user action cuts parse.                    ##
+## ------------------------------------------------------------------------- ##
+
+AT_SETUP([Corrupted semantic options if user action cuts parse.])
+
+AT_DATA_GRAMMAR([glr-regr10.y],
+[[
+%{
+# include <stdio.h>
+  static void yyerror (char const *);
+  static int yylex (void);
+  #define GARBAGE_SIZE 50
+  static char garbage[GARBAGE_SIZE];
+%}
+
+%glr-parser
+%union { char *ptr; }
+%type <ptr> start
+
+%%
+
+start:
+    %dprec 2 { $$ = garbage; YYACCEPT; }
+  | %dprec 1 { $$ = garbage; YYACCEPT; }
+  ;
+
+%%
+
+static void
+yyerror (char const *msg)
+{
+  fprintf (stderr, "%s\n", msg);
+}
+
+static int
+yylex (void)
+{
+  return 0;
+}
+
+int
+main (void)
+{
+  int index;
+  for (index = 0; index < GARBAGE_SIZE; index+=1)
+    garbage[index] = 132;
+  return yyparse ();
+}
+]])
+
+AT_CHECK([[bison -t -o glr-regr10.c glr-regr10.y]], 0, [],
+[glr-regr10.y: conflicts: 1 reduce/reduce
+])
+AT_COMPILE([glr-regr10])
+
+AT_CHECK([[./glr-regr10]], 0, [], [])
+
+AT_CLEANUP
+
+
+## ------------------------------------------------------------------------- ##
+## Undesirable destructors if user action cuts parse.                       ##
+## ------------------------------------------------------------------------- ##
+
+AT_SETUP([Undesirable destructors if user action cuts parse.])
+
+AT_DATA_GRAMMAR([glr-regr11.y],
+[[
+%{
+# include <stdlib.h>
+  static void yyerror (char const *);
+  static int yylex (void);
+  static int destructors = 0;
+# define USE(val)
+%}
+
+%glr-parser
+%union { int dummy; }
+%type <int> 'a'
+%destructor { destructors += 1; } 'a'
+
+%%
+
+start:
+    'a' %dprec 2 { USE ($1); destructors += 1; YYACCEPT; }
+  | 'a' %dprec 1 { USE ($1); destructors += 1; YYACCEPT; }
+  ;
+
+%%
+
+static void
+yyerror (char const *msg)
+{
+  fprintf (stderr, "%s\n", msg);
+}
+
+static int
+yylex (void)
+{
+  static char const *input = "a";
+  return *input++;
+}
+
+int
+main (void)
+{
+  int exit_status = yyparse ();
+  if (destructors != 1)
+    {
+      fprintf (stderr, "Destructor calls: %d\n", destructors);
+      return 1;
+    }
+  return exit_status;
+}
+]])
+
+AT_CHECK([[bison -t -o glr-regr11.c glr-regr11.y]], 0, [],
+[glr-regr11.y: conflicts: 1 reduce/reduce
+])
+AT_COMPILE([glr-regr11])
+
+AT_CHECK([[./glr-regr11]], 0, [], [])
+
+AT_CLEANUP
+
+
+## ------------------------------------------------------------------------- ##
+## Leaked merged semantic value if user action cuts parse.                  ##
+## ------------------------------------------------------------------------- ##
+
+AT_SETUP([Leaked merged semantic value if user action cuts parse.])
+
+AT_DATA_GRAMMAR([glr-regr12.y],
+[[
+%glr-parser
+%union { int dummy; }
+%type <dummy> start
+%destructor { has_value = 0; } start
+
+%{
+# include <stdlib.h>
+  static int merge (YYSTYPE, YYSTYPE);
+  static void yyerror (char const *);
+  static int yylex (void);
+  static int has_value = 0;
+# define USE(val)
+%}
+
+%%
+
+start:
+    %merge<merge> { has_value = 1; USE ($$); }
+  | %merge<merge> { USE ($$); YYACCEPT; }
+  ;
+
+%%
+
+static int
+merge (YYSTYPE s1, YYSTYPE s2)
+{
+  /* Not invoked. */
+  return 0;
+}
+
+static void
+yyerror (char const *msg)
+{
+  fprintf (stderr, "%s\n", msg);
+}
+
+static int
+yylex (void)
+{
+  return 0;
+}
+
+int
+main (void)
+{
+  int exit_status = yyparse ();
+  if (has_value)
+    {
+      fprintf (stderr, "Destructor not called.\n");
+      return 1;
+    }
+  return exit_status;
+}
+]])
+
+AT_CHECK([[bison -t -o glr-regr12.c glr-regr12.y]], 0, [],
+[glr-regr12.y: conflicts: 1 reduce/reduce
+])
+AT_COMPILE([glr-regr12])
+
+AT_CHECK([[./glr-regr12]], 0, [], [])
+
+AT_CLEANUP