Re: [RFA] Handle BINOP_INTDIV in valarith.c

Joel Brobecker
2008-01-23T23:09:52Z

> I wrote the floatdiv version, which allows me to easily force the
> conversion to double formats for left and right operand:

Right, but you are doing the conversion inside what I call "core-gdb",
which is a language-independent file. As a result, you ended up needing
a new operator. But the creation of this new operator would not be
necessary if you handled BINOP_DIV in a pascal-specific way.

> maybe
> || (op == BINOP_DIV && current_language = language_pascal))

That's not the proper way of doing this. What you need to do is to
setup your language to have a pascal-specific expression evaluator.
Right now, it's set to use the "standard" expression evaluator which
(IIRC) is the C evaluator. Your pascal expression evaluator will
defer back to the standard expression evaluator most of the time,
except for the case when the binary operator is FLOAT_DIV. In this
case, you'll do the division yourself.

You can have a look at ada-lang.c:ada_evaluate_subexp(). It's a large
routine because of a lot of stuff is special to Ada, but you'll also
see:

op = exp->elts[pc].opcode;
[...]
switch (op)
{
default:
*pos -= 1;
arg1 = evaluate_subexp_standard (expect_type, exp, pos, noside);
[...]
case BINOP_DIV:
arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
if (noside == EVAL_SKIP)
goto nosideret;
else if (noside == EVAL_AVOID_SIDE_EFFECTS
&& (op == BINOP_DIV || op == BINOP_REM || op == BINOP_MOD))
return value_zero (value_type (arg1), not_lval);
else
{
if (ada_is_fixed_point_type (value_type (arg1)))
arg1 = cast_from_fixed_to_double (arg1);
if (ada_is_fixed_point_type (value_type (arg2)))
arg2 = cast_from_fixed_to_double (arg2);
return ada_value_binop (arg1, arg2, op);
}

If you look at the "default:" case, you'll see that we let
the standard evaluator do the work for us. But we treat the
BINOP_DIV case specially: First we evaluate each side of our
division, and then perform the division and return the result.

This ada_evaluate_subexp routine is setup in the language through
the exp_descriptor structure.

--
Joel