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
This makes '/' and the actual root of VFS distinguishable. A VFS root
may contain one ore more '/' entries for each file system. 'opendir' for
the VFS root opens all file systems via 'open_composite_dir', while
'opendir' for '/' only returns a VFS handle.
Fixes#2569
The VFS library can be used in single-threaded or multi-threaded
environments and depending on that, signals are handled by the same thread
which uses the VFS library or possibly by a different thread. If a VFS
plugin needs to block to wait for a signal, there is currently no way
which works reliably in both environments.
For this reason, this commit makes the interface of the VFS library
nonblocking, similar to the File_system session interface.
The most important changes are:
- Directories are created and opened with the 'opendir()' function and the
directory entries are read with the recently introduced 'queue_read()'
and 'complete_read()' functions.
- Symbolic links are created and opened with the 'openlink()' function and
the link target is read with the 'queue_read()' and 'complete_read()'
functions and written with the 'write()' function.
- The 'write()' function does not wait for signals anymore. This can have
the effect that data written by a VFS library user has not been
processed by a file system server yet when the library user asks for the
size of the file or closes it (both done with RPC functions at the file
system server). For this reason, a user of the VFS library should
request synchronization before calling 'stat()' or 'close()'. To make
sure that a file system server has processed all write request packets
which a client submitted before the synchronization request,
synchronization is now requested at the file system server with a
synchronization packet instead of an RPC function. Because of this
change, the synchronization interface of the VFS library is now split
into 'queue_sync()' and 'complete_sync()' functions.
Fixes#2399
The support has two parts. First, a VFS plugin now gets passed an
I/O-response handler callback on construction, which informs users of the
VFS that an I/O event occurred. This enables, for example, the libC to
check if blocking read can be completed. Further, the VFS file I/O
interface provides now functions for suspendable reads, i.e.,
queue_read() and complete_read().
Besides adapting the components to the use of base/log.h, the patch
cleans up a few base headers, i.e., it removes unused includes from
root/component.h, specifically base/heap.h and
ram_session/ram_session.h. Hence, components that relied on the implicit
inclusion of those headers have to manually include those headers now.
While adjusting the log messages, I repeatedly stumbled over the problem
that printing char * arguments is ambiguous. It is unclear whether to
print the argument as pointer or null-terminated string. To overcome
this problem, the patch introduces a new type 'Cstring' that allows the
caller to express that the argument should be handled as null-terminated
string. As a nice side effect, with this type in place, the optional len
argument of the 'String' class could be removed. Instead of supplying a
pair of (char const *, size_t), the constructor accepts a 'Cstring'.
This, in turn, clears the way let the 'String' constructor use the new
output mechanism to assemble a string from multiple arguments (and
thereby getting rid of snprintf within Genode in the near future).
To enforce the explicit resolution of the char * ambiguity, the 'char *'
overload of the 'print' function is marked as deleted.
Issue #1987
Opening a VFS handle previously involved allocating from the global heap
at each VFS file system. By amending open with an allocator argument,
dynamic allocation can be partitioned.
A new close method is used to deallocate open handles.
Issue #1751
Issue #1891
When returning early on directory operations, file systems that might
be able to handle the request but come after the current one are not
tried.
Fixes#1400.
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
