parse.lac: implement as %define variable.

[bison.git] / ChangeLog

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+2010-12-11  Joel E. Denny  <jdenny@clemson.edu>
+
+       parse.lac: implement as %define variable.
+       LAC = lookahead correction.  See discussion at
+       <http://lists.gnu.org/archive/html/bison-patches/2009-09/msg00034.html>.
+       However, one point there must be corrected: because of %nonassoc,
+       LAC is *not* always redundant for lr.type=canonical-lr.
+       * data/yacc.c: Accept values of "none" (default) or "full" for
+       parse.lac.  Accept %define parse.lac.es-capacity to specify
+       capacity of LAC's temporary exploratory stack.  It defaults to 20
+       and, for now, will not grow dynamically.
+       (b4_lac_flag, b4_lac_if): New m4 macros.  Evaluate as true for
+       parse.lac!=none.
+       (YYBACKUP): Invoke YY_LAC_DISCARD.
+       (YY_LAC_ESTABLISH, YY_LAC_DISCARD): New cpp macros that invoke
+       yy_lac and track when it needs to be invoked
+       (yy_lac): New function that, given the current stack, determines
+       whether a token can eventually be shifted.  Return status mimics
+       yyparse return status.
+       (yysyntax_error): Change yystate argument to yyssp so stack top
+       can be passed to yy_lac.  If LAC is requested, build expected
+       token list by invoking yy_lac for every token instead of just
+       checking the current state for lookaheads.  Return 2 if yy_lac
+       exhausts memory.
+       (yyparse, yypush_parse): Use local variable yy_lac_established and
+       cpp macros YY_LAC_ESTABLISH and YY_LAC_DISCARD to implement LAC.
+       Update yysyntax_error invocation.  Add yyexhaustedlab code if LAC
+       is requested.
+       * tests/conflicts.at (%nonassoc and eof): Extend to check the
+       effect of each of -Dlr.type=canonical-lr and -Dparse.lac=full.
+       (parse.error=verbose and consistent errors): Likewise.
+       (LAC: %nonassoc requires splitting canonical LR states): New test
+       group demonstrating how LAC can fix canonical LR.
+       * tests/input.at (LAC: Errors for %define): New test group.
+       * tests/regression.at (LAC: Exploratory stack): New test group.
+       (LAC: Memory exhaustion): New test group.
+
 2010-11-21  Joel E. Denny  <jdenny@clemson.edu>
 
        build: use gnulib's new bootstrap_sync option.