Hi C++ folks,
There are a number of places in the coroutine codegen where we need to
build calls to promise methods.
Such methods can, in several cases, also be constexpr or static (or both)
which leads to the PR,
Now the mechanism I use is this;
1/ lookup the method in the relevant scope
tree method
= lookup_member (promise, member_id, /*protect=*/1, /*want_type=*/0,
tf_warning_or_error);
- this returns a BASELINK tree..
2/ In many cases, the calls are to methods with no parms.
so, with a dummy object, I do:
tree call
= build_new_method_call (dummy, method, NULL, NULL_TREE, LOOKUP_NORMAL, NULL,
flags);
‘args’ is the 3rd parm.
3/ The header comment on build_new_method_call says:
/* Build a call to "INSTANCE.FN (ARGS)". If FN_P is non-NULL, it will
be set, upon return, to the function called. ARGS may be NULL.
This may change ARGS. */
Which says that the 3rd arg can validly be NULL (as per my example).
4/ however, inside build_new_method_call ‘args' gets assigned to
‘user_args’ which is used in a lot of places without any guard to see if
it’s non-null. One of those places is passing it to add_candidates (),
which eventually in the case of a static method uses the pointer and ICEs.
=====
So…
A/ I’m doing something wrong, and my use of APIs is violating an
expectation (in which case what’s the right API usage?)
B/ It happens to be other callers to build_new_method_call() have either
had dummy args or not produced the same set of conditions
(for my case of static promise methods)
* if I provide an empty dummy ‘args' to the build_new_method_call it works
* if I fix the unguarded use of ‘args' in add_candidates (as below) it works,
AFAICT, the intent is to avoid every caller for build_new_method_call()
having to build a dummy argument list when that list is empty - it would
seem irritating to have to add one for every use in coros - but I can.
WDYT?
thanks
Iain
--------
the fix for call.c:
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 3c97b9846e2..dccc1bf596f 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -5862,7 +5862,7 @@ add_candidates (tree fns, tree first_arg, const
vec<tree, va_gc> *args,
}
/* Don't bother reversing an operator with two identical parameters. */
- else if (args->length () == 2 && (flags & LOOKUP_REVERSED))
+ else if (args && args->length () == 2 && (flags & LOOKUP_REVERSED))
{
tree parmlist = TYPE_ARG_TYPES (TREE_TYPE (fn));
if (same_type_p (TREE_VALUE (parmlist),
