The current approach was too adhoc: the symbols were not sufficiently
self-contained, in particular wrt memory management. The "new"
guideline is the one that should have been followed from the start:
let the symbols handle themslves, instead of leaving their users to
it. It was justified by the will to avoid gratuitious moves and
copies, but the current approach does not seem to be slower, yet it
will probably be simpler to adjust to support move semantics from
C++11.
The documentation says that the %parse-param are available from the
%destructor. In retrospect, that was a silly design decision, which
we can break for variants, as its a new feature. It should be phased
out for non-variants too.
* data/variant.hh: A variant never knows if it stores something or
not, it is up to its users to store this information.
Yet, in parse.assert mode, make sure the empty/filled variants
are properly used.
(b4_symbol_constructor_define_): Don't call directly the symbol
constructor, to save a useless temporary.
* data/stack.hh (push): Steal the pushed value instead of duplicating
it.
This will simplify the callers of push, who handled this "move"
approach themselves.
* data/c++.m4 (basic_symbol): Let -1, as kind, denote the fact that
a symbol is empty.
This is needed for instance when shifting the lookahead: yyla
is given as argument to "push", and its value is then moved on
the stack. But then yyla must be declared "empty" so that its
destructor won't be called.
(basic_symbol::move): New.
Move the responsibility of calling the destructor from yy_destroy
to ~basic_symbol in the case of variants.
* data/lalr1.cc (stack_symbol_type): Now a derived class from its
previous value, so that we can add a constructor from a symbol_type.
(by_state): State -1 means empty.
(yypush_): Factor, by calling one overload from the other one, and
using the new semantics of stack::push.
No longer reclaim by hand the memory from rhs symbols, since now
that we store objects with proper destructors, they will be reclaimed
automatically.
Conversely, be sure to delete yylhs.
* tests/c++.at (C++ Variant-based Symbols): New "unit" test for
symbols.
* data/c++.m4 (basic_symbol): Keep 'inline' in the prototypes, but don't
duplicate it in the implementation.
* data/variant.hh (variant): 'inline' is not needed when the implementation is
provided in the class definition.
* data/variant.hh (variant, operator=): Make private.
* data/c++.m4 (operator=): New, to avoid needing a definition of that operator
for each class member (such as a possible variant).
* data/glr.cc, data/lalr.cc: Add the necessary include for the abort.
The "variant" structure provides a means to store, in a typeless way,
C++ objects. Manipulating it without provide the type of the stored
content is doomed to failure. So provide a means to copy in a type
safe way, and prohibit typeless assignments.
* data/c++.m4 (symbol_type::move): New.
* data/lalr1.cc: Use it.
* data/variant.hh (b4_variant_define): Provide variant::copy.
Let variant::operator= abort.
We cannot undefine it, yet, as it is still uses by the implicit
assigment in symbols, which must also be disabled.
Equip variants with more checking code. Provide a means to request
includes.
* data/variant.hh (b4_variant_includes): New.
* data/lalr1.cc: Use it.
* data/variant.hh (variant::built): Define at the end, as a private member.
(variant::tname): New.
Somewhat makes "built" useless, but let's keep both for a start, in
case using "typeinfo" is considered unacceptable in some environments.
Fix some formatting issues.
* data/c++.m4, data/lalr1.cc (parser::symbol_type): Change the
constructor to take a token_type instead of the (internal) symbol
number.
Call yytranslate_.
* data/variant.hh (b4_symbol_constructor_define_): Therefore,
don't call yytranslate_ here.
* data/c++.m4 (b4_symbol_constructor_declare)
(b4_symbol_constructor_define): New empty stubs.
(b4_public_types_declare, b4_public_types_define): Use them.
* data/lalr1.cc (b4_symbol_constructor_declare)
(b4_symbol_constructor_declare_)
(b4_symbol_constructor_define_, b4_symbol_constructor_define):
Move to...
* data/variant.hh: here.
Remove the "b4_variant_if" parts, as variant.hh is loaded only if
needed.
* data/lalr1.cc: No longer invoke b4_symbol_constructor_define and
b4_symbol_constructor_declare, as it is now done by
b4_public_types_define and b4_public_types_declare.
* data/c++.m4 (b4_semantic_type_declare): New.
Factors and generalizes what was in glr.cc and lalr1.cc.
* data/variant.hh (b4_semantic_type_declare): Redefine it for
variants.
* data/lalr1.cc, data/glr.cc: Use it.
