FYI: Fix leaked semantic values when reporting ambiguity

[Joel E. Denny]

In this patch, returning yyabort from yyreportAmbiguity seems to be fine 
for now.  Should there be a new result tag for it instead?

I'd like to weed out longjmp from "glr.c" as I find time.  In some cases, 
I might be able to write a test case to show a functionality problem.  In 
others, I'd like to get rid of it just to improve code readability.  Any 
objections?

Joel

2006-03-02  Joel E. Denny  <address@hidden>

        Avoid memory leaks by not invoking longjmp in yyreportAmbiguity.
        * tests/glr-regression.at (Leaked semantic values when reporting
        ambiguity): New test case.
        * data/glr.c (yyreportAmbiguity): Invoke yyyerror directly and return
        yyabort rather than invoking yyFail, which invokes longjmp.  Remove the
        now unnecessary yystackp parameter.
        (yyresolveValue): Return yyreportAmbiguity's result.  Now the necessary
        destructors can be called.

        * tests/glr-regression.at: Don't invoke bison with `-t' unnecessarily
        in existing testcases.

Index: data/glr.c
===================================================================
RCS file: /sources/bison/bison/data/glr.c,v
retrieving revision 1.165
diff -p -u -r1.165 glr.c
--- data/glr.c  2 Mar 2006 01:35:15 -0000       1.165
+++ data/glr.c  2 Mar 2006 05:58:00 -0000
@@ -1783,12 +1783,9 @@ yyreportTree (yySemanticOption* yyx, int
 }
 #endif
 
-static void yyreportAmbiguity (yySemanticOption* yyx0, yySemanticOption* yyx1,
-                              yyGLRStack* yystackp]b4_pure_formals[)
-  __attribute__ ((__noreturn__));
-/*ARGSUSED*/ static void
-yyreportAmbiguity (yySemanticOption* yyx0, yySemanticOption* yyx1,
-                  yyGLRStack* yystackp]b4_pure_formals[)
+/*ARGSUSED*/ static YYRESULTTAG
+yyreportAmbiguity (yySemanticOption* yyx0,
+                  yySemanticOption* yyx1]b4_pure_formals[)
 {
   YYUSE (yyx0);
   YYUSE (yyx1);
@@ -1801,7 +1798,9 @@ yyreportAmbiguity (yySemanticOption* yyx
   yyreportTree (yyx1, 2);
   YYFPRINTF (stderr, "\n");
 #endif
-  yyFail (yystackp][]b4_pure_args[, YY_("syntax is ambiguous"));
+
+  yyerror (]b4_yyerror_args[YY_("syntax is ambiguous"));
+  return yyabort;
 }
 
 
@@ -1838,7 +1837,7 @@ yyresolveValue (yyGLRState* yys, yyGLRSt
          switch (yypreference (yybest, yyp))
            {
            case 0:
-             yyreportAmbiguity (yybest, yyp, yystackp]b4_pure_args[);
+             return yyreportAmbiguity (yybest, yyp]b4_pure_args[);
              break;
            case 1:
              yymerge = yytrue;
Index: tests/glr-regression.at
===================================================================
RCS file: /sources/bison/bison/tests/glr-regression.at,v
retrieving revision 1.30
diff -p -u -r1.30 glr-regression.at
--- tests/glr-regression.at     2 Mar 2006 01:35:15 -0000       1.30
+++ tests/glr-regression.at     2 Mar 2006 05:58:00 -0000
@@ -864,7 +864,7 @@ main (void)
 }
 ]])
 
-AT_CHECK([[bison -t -o glr-regr10.c glr-regr10.y]], 0, [],
+AT_CHECK([[bison -o glr-regr10.c glr-regr10.y]], 0, [],
 [glr-regr10.y: conflicts: 1 reduce/reduce
 ])
 AT_COMPILE([glr-regr10])
@@ -930,7 +930,7 @@ main (void)
 }
 ]])
 
-AT_CHECK([[bison -t -o glr-regr11.c glr-regr11.y]], 0, [],
+AT_CHECK([[bison -o glr-regr11.c glr-regr11.y]], 0, [],
 [glr-regr11.y: conflicts: 1 reduce/reduce
 ])
 AT_COMPILE([glr-regr11])
@@ -1059,7 +1059,7 @@ main (void)
 }
 ]])
 
-AT_CHECK([[bison -t -o glr-regr12.c glr-regr12.y]], 0, [],
+AT_CHECK([[bison -o glr-regr12.c glr-regr12.y]], 0, [],
 [glr-regr12.y: conflicts: 1 shift/reduce, 1 reduce/reduce
 ])
 AT_COMPILE([glr-regr12])
@@ -1186,7 +1186,7 @@ main (void)
 }
 ]])
 
-AT_CHECK([[bison -t -o glr-regr13.c glr-regr13.y]], 0, [], [])
+AT_CHECK([[bison -o glr-regr13.c glr-regr13.y]], 0, [], [])
 AT_COMPILE([glr-regr13])
 
 AT_CHECK([[./glr-regr13]], 0,
@@ -1399,7 +1399,7 @@ main (void)
 }
 ]])
 
-AT_CHECK([[bison -t -o glr-regr14.c glr-regr14.y]], 0, [],
+AT_CHECK([[bison -o glr-regr14.c glr-regr14.y]], 0, [],
 [glr-regr14.y: conflicts: 3 reduce/reduce
 ])
 AT_COMPILE([glr-regr14])
@@ -1420,3 +1420,95 @@ start <- merge 'c' stack_explosion:
 ], [])
 
 AT_CLEANUP
+
+
+## ------------------------------------------------------------------------- ##
+## Leaked semantic values when reporting ambiguity.                         ##
+## ------------------------------------------------------------------------- ##
+
+AT_SETUP([Leaked semantic values when reporting ambiguity])
+
+AT_DATA_GRAMMAR([glr-regr15.y],
+[[
+%glr-parser
+%union { int dummy; }
+%type <dummy> parent_rhs_before
+%destructor { parent_rhs_before_value = 0; } parent_rhs_before
+
+%{
+# include <stdlib.h>
+  static void yyerror (char const *);
+  static int yylex (void);
+  static int parent_rhs_before_value = 0;
+# define USE(val)
+%}
+
+%%
+
+start:
+  alt1 %dprec 1
+  | alt2 %dprec 2
+  ;
+
+/* This stack must be merged into the other stacks *last* (added at the
+   beginning of the semantic options list) so that yyparse will choose to clean
+   it up rather than the tree for which some semantic actions have been
+   performed.  Thus, if yyreportAmbiguity longjmp's to yyparse, the values from
+   those other trees are not cleaned up.  */
+alt1: ;
+
+alt2:
+  parent_rhs_before ambiguity {
+    USE ($1);
+    parent_rhs_before_value = 0;
+  }
+  ;
+
+parent_rhs_before:
+  {
+    USE ($$);
+    parent_rhs_before_value = 1;
+  }
+  ;
+
+ambiguity: ambiguity1 | ambiguity2 ;
+ambiguity1: ;
+ambiguity2: ;
+
+%%
+
+static void
+yyerror (char const *msg)
+{
+  fprintf (stderr, "%s\n", msg);
+}
+
+static int
+yylex (void)
+{
+  return 0;
+}
+
+int
+main (void)
+{
+  int exit_status = yyparse () != 1;
+  if (parent_rhs_before_value)
+    {
+      fprintf (stderr, "`parent_rhs_before' destructor not called.\n");
+      exit_status = 1;
+    }
+  return exit_status;
+}
+]])
+
+AT_CHECK([[bison -o glr-regr15.c glr-regr15.y]], 0, [],
+[glr-regr15.y: conflicts: 2 reduce/reduce
+])
+AT_COMPILE([glr-regr15])
+
+AT_CHECK([[./glr-regr15]], 0, [],
+[syntax is ambiguous
+])
+
+AT_CLEANUP