Clang is generally fine with Genode::List and compiles code using it
without emitting any warnings. There is however one exception. Clang
fails hard when building base-hw/src/core/kernel/object.cc.
This is due to a call to Genode::List::remove made from
Object_identity::invalidate function. The error message clang
produces is:
list.h:96:33: error: 'Genode::List<Kernel::Object_identity_reference>::Element::_next'
is not a member of class 'const Kernel::Object_identity'
_first = le->List::Element::_next;
~~~~~~~~~~~~~~~^
When we look at the declaration of the Kernel::Object class on which
the remove method is called. as expected it does inherit Genode::List:
using Object_identity_list
= Genode::List<Kernel::Object_identity>;
class Kernel::Object : private Object_identity_list
{
...
}
Given the error message we see that List::Element should be resolved to
Genode::List<Kernel::Object_identity>::Element, and not
Genode::List<Kernel::Object_identity_reference>::Element. But how does
clang manage to figure out we're talking about Object_identity_refecence
list here? Well, I admit I don't know the exact steps it takes to arrive
at this conclusion, but it is not entirely wrong. If we take a look at
what Kernel::Object_identity is we'll see:
class Kernel::Object_identity
: public Object_identity_list::Element,
public Kernel::Object_identity_reference_list
{
...
}
Where as one can guess Object_identity_reference_list is defined as:
using Object_identity_reference_list
= Genode::List<Object_identity_reference>;
Long story short Kernel::Object has Genode::List of both Kernel::Object_identity
and Kernel::Object_identity_reference in its inheritance chain and clang
is not really sure to which of those the code refers to in
Genode::List::remove method by using List::Element::.
The fix for this is relatively simple, explicitly state the full type of
the base class the code intends to refer to. Replacing List::Element,
with List<LT>::Element makes the code buildable with both clang and GCC.
Fixes#3990
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
