glr2.cc: fix pointer arithmethics

A glr_state keeps tracks of its predecessor using an offset relative
to itself (i.e., pointer subtraction).  Unfortunately we sometimes
have to compute offsets for pointers that live in different
containers, in particular in yyfillin.  In that case there is no
reason for the distance between the two objects to be a multiple of
the object size (0x40 on my machine), and the resulting ptrdiff_t may
be "wrong", i.e., it does allow to recover one from the other.  We
cannot use "typed" pointer arithmetics here, the Euclidean division
has it wrong.  So use "plain" char* pointers.

Fixes 718 (Duplicate representation of merged trees: glr2.cc) and
examples/c++/glr/c++-types.

Still XFAIL:

    712: Improper handling of embedded actions and dollar(-N) in GLR parsers: glr2.cc
    730: Incorrectly initialized location for empty right-hand side in GLR: glr2.cc
    748: Incorrect lookahead during nondeterministic GLR: glr2.cc

* data/skeletons/glr2.cc (glr_state::as_pointer_): New.
(glr_state::pred): Use it.
* examples/c++/glr/c++-types.test: The test passes.
* tests/glr-regression.at (Duplicate representation of merged trees:
glr2.cc): Passes.

1 files changed, 3 insertions, 0 deletions

diff --git a/TODO b/TODO
index e1bcb8d1..b857199a 100644
--- a/TODO
+++ b/TODO
@@ -202,6 +202,9 @@ parser::location_type.  Undefine YYSTYPE and YYLTYPE.
 Currently all the assertions are enabled.  Once we are confident in glr2.cc,
 let parse.assert use the same approach as in lalr1.cc.
 
+*** debug_stream
+Stop using std::cerr everywhere.
+
 *** glr.c
 When glr2.cc fully replaces glr.cc, get rid of the glr.cc scaffolding in
 glr.c.