The namespace draws a clear line between the base library and the core
component.
It is declared at the new core-local header <types.h>, which is expected
to be included by all code of the core component. It is thereby a
natural place for kernel-agnostic general types like commonly used C++
utilities.
Fixes#4777
For the constructor of Kernel_object<T> there are two variants. One for the
case that it is called from Core where the kernel object (type T) must be
created via a syscall and one when it is called from within the kernel and the
kernel object can be created directly. Selecting one of these variants was done
using a bool argument to the constructor. However, this implies that the
constructor of Kernel_object<T> and that of T have the same signature in the
variadic arguments, even in the syscall case, although technically it would
then not be necessary.
This becomes a problem as soon as kernel objects created by Core shall receive
additional arguments from the kernel, for instance a reference to the global
CPU pool, and therefore stands in the way when wanting to get rid of global
statics in the kernel. Therefore, this commit introduces two constructors that
are selected through enum arguments:
! Kernel_object(Called_from_kernel, ...);
! Kernel_object(Called_from_core, ...);
Ref #4217
Improve consistency with the other base repositories, in particular
- Indentation of class initializers
- Vertical whitespace around control-flow statements
- Preferably place control-flow statements (return, break, continue) at
beginning of a line
- Placing the opening brace of a namespace at the end of line
- Placing the opening brace of a class at a new line
- Removing superfluous braces around single statements
- Two empty lines between methods/functions in implementation files
This patch replaces the former prominent use of pointers by references
wherever feasible. This has the following benefits:
* The contract between caller and callee becomes more obvious. When
passing a reference, the contract says that the argument cannot be
a null pointer. The caller is responsible to ensure that. Therefore,
the use of reference eliminates the need to add defensive null-pointer
checks at the callee site, which sometimes merely exist to be on the
safe side. The bottom line is that the code becomes easier to follow.
* Reference members must be initialized via an object initializer,
which promotes a programming style that avoids intermediate object-
construction states. Within core, there are still a few pointers
as member variables left though. E.g., caused by the late association
of 'Platform_thread' objects with their 'Platform_pd' objects.
* If no pointers are present as member variables, we don't need to
manually provide declarations of a private copy constructor and
an assignment operator to avoid -Weffc++ errors "class ... has
pointer data members [-Werror=effc++]".
This patch also changes a few system bindings on NOVA and Fiasco.OC,
e.g., the return value of the global 'cap_map' accessor has become a
reference. Hence, the patch touches a few places outside of core.
Fixes#3135
The patch adjust the code of the base, base-<kernel>, and os repository.
To adapt existing components to fix violations of the best practices
suggested by "Effective C++" as reported by the -Weffc++ compiler
argument. The changes follow the patterns outlined below:
* A class with virtual functions can no longer publicly inherit base
classed without a vtable. The inherited object may either be moved
to a member variable, or inherited privately. The latter would be
used for classes that inherit 'List::Element' or 'Avl_node'. In order
to enable the 'List' and 'Avl_tree' to access the meta data, the
'List' must become a friend.
* Instead of adding a virtual destructor to abstract base classes,
we inherit the new 'Interface' class, which contains a virtual
destructor. This way, single-line abstract base classes can stay
as compact as they are now. The 'Interface' utility resides in
base/include/util/interface.h.
* With the new warnings enabled, all member variables must be explicitly
initialized. Basic types may be initialized with '='. All other types
are initialized with braces '{ ... }' or as class initializers. If
basic types and non-basic types appear in a row, it is nice to only
use the brace syntax (also for basic types) and align the braces.
* If a class contains pointers as members, it must now also provide a
copy constructor and assignment operator. In the most cases, one
would make them private, effectively disallowing the objects to be
copied. Unfortunately, this warning cannot be fixed be inheriting
our existing 'Noncopyable' class (the compiler fails to detect that
the inheriting class cannot be copied and still gives the error).
For now, we have to manually add declarations for both the copy
constructor and assignment operator as private class members. Those
declarations should be prepended with a comment like this:
/*
* Noncopyable
*/
Thread(Thread const &);
Thread &operator = (Thread const &);
In the future, we should revisit these places and try to replace
the pointers with references. In the presence of at least one
reference member, the compiler would no longer implicitly generate
a copy constructor. So we could remove the manual declaration.
Issue #465
