On 04/22/2014 02:56 PM, Richard Sandiford wrote:
David Malcolm <dmalc...@redhat.com> writes:
Alternatively we could change the is-a.h API to eliminate this
discrepancy, and keep the typedefs; giving something like the following:
static void
dump_gimple_switch (pretty_printer *buffer, gimple_switch gs, int spc,
int flags)
[...snip...]
[...later, within pp_gimple_stmt_1:]
case GIMPLE_SWITCH:
dump_gimple_switch (buffer, as_a <gimple_switch> (gs), spc, flags);
break;
which is concise, readable, and avoid the change in pointerness compared
to the "gimple" typedef; the local decls above would look like this:
gimple some_stmt; /* note how this doesn't have a star... */
gimple_assign assign_stmt; /* ...and neither do these */
gimple_cond assign_stmt;
gimple_phi phi;
I think this last proposal is my preferred API, but it requires the
change to is-a.h
Attached is a proposed change to the is-a.h API that elimintates the
discrepancy, allowing the use of typedefs with is-a.h (doesn't yet
compile, but hopefully illustrates the idea). Note how it changes the
API to match C++'s dynamic_cast<> operator i.e. you do
Q* q = dyn_cast<Q*> (p);
not:
Q* q = dyn_cast<Q> (p);
Thanks for being flexible. :-) I like this version too FWIW, for the
reason you said: it really does look like a proper C++ cast.
If we ever decide to get rid of the typedefs (maybe at the same time as
using "auto") then the choice might be different, but that would be a much
more systematic and easily-automated change than this one.
Can we also consider making dyn_cast handle NULL at the same time? the
C++ dynamic_cast<> does, and I ended up supporting it in my branch as well.
so dyn_cast would be more like:
inline T
dyn_cast (U *p)
{
if (p && is_a <T> (p))
return is_a_helper <T>::cast (p);
else
return static_cast <T > (0);
}
both is_a<> and as_a<> would still require a valid pointer or you get a
NULL dereference...
I've found it very pragmatic...
Andrew
