genode/doc/release_notes-19-02.txt

              ===============================================
              Release notes for the Genode OS Framework 19.02
              ===============================================

                               Genode Labs



In our [https://genode.org/about/road-map - road map] for 2019, we stated
our goal to make Genode more relevant and appealing for a broader community.
The current release takes a big leap towards that goal: It opens up Sculpt
OS for 3rd-party software providers, introduces a federated blogging
platform about Genode-related topics, and makes the world's
[https://www.tiobe.com/tiobe-index/ - most popular] programming language
(Java) available to Genode users.

With the 4th stage of the evolution of Sculpt OS - themed as "community
experience" (CE) - Genode's custom general-purpose OS introduces a novel and
simple way for users to discover software, and for software providers to
announce software. There is no middle man like an app store or a distribution!
We hope that this federated model of software provisioning and deployment will
have a vitalizing effect on the community around Genode. On a practical level,
the interactivity of the new version is a playful and fun experience. Section
[Sculpt OS as a community experience (CE)] gives a rough overview about
*Sculpt CE*. A ready-to-use disk image will be released mid of March.

When speaking of "software providers", we don't think of anonymous
repositories. Software - and Free Software in particular - is developed and
provided by individuals after all. So in our federated way of software
distribution, we want to highlight this individuality. For this reason, we
launched a new blogging platform for Genode-related stories called
[https://genodians.org - Genodians.org], which gives everyone who is
enthusiastic about Genode - users and developers alike - a platform to express
ideas, announce software, or share practical tips and tricks. As explained in
the [https://genodians.org/nfeske/2019-01-07-welcome - initial posting],
*Genodians.org* is - in the spirit of Sculpt's software distribution model -
also organized in a federated way. The content is hosted and remains
completely under control by the respective authors. The website merely
aggregates and presents the content. It goes without saying that Genodians.org
is based on Genode. The system image that contains the entire web appliance -
from the kernel over the content management to the web server - is contained
in a 8 MiB disk image.
Section [Genodians.org as a showcase of a Genode-based web appliance] goes
into more detail.

We identified the support of popular programming languages as one key aspect
to attract a broader community. With the current release, our port of
*OpenJDK* (Section [Java]) for both 64-bit x86 and 32-bit ARM has reached a
mature state suitable for the creation of web services. This paves the way
towards quite exciting new system creations, like the *Boot2Java* system
presented in Section [Showcase of a Java-based network appliance].
On the account of programming-language support, we are happy to announce
a vastly improved runtime support for *Ada* and *SPARK* (Section
[Ada and SPARK] as well as the initial support for OCaml (Section [OCaml]).

Besides the work on shiny features, the current release cycle included a
profound *spring cleanup* described in Section
[Base framework and OS-level infrastructure].
It thereby finalizes the huge API modernization initiated almost three years
ago.


Sculpt OS as a community experience (CE)
########################################

When we laid out the road map for Sculpt OS a little more than one year ago,
we envisioned four stages of development. Sculpt EA was geared towards
die-hard early adopters facilitating the live editing of the system using a
text editor. Sculpt TC was targeted at "the curious" and included a graphical
user interface for common administrative tasks. Sculpt VC introduced the
visual composition of the system using an interactive graph. Even though
Sculpt already allowed for the installation of components from different
software providers at this stage, it offered no simple means to discover
software and the installation still required the manual editing of "launcher"
text files.

The final - community experience - stage of the plan ought to foster the
federated provisioning of software. Software providers should have the ability
to announce new packages. Conversely, users should be able to "subscribe" to
such announcements, similar how one would subscribe to an RSS feed. Once
software is discovered in this way, it should take only a few clicks to
install and integrate it into the running Sculpt system. No command-line
interface should stand in the way of discovery.

Sculpt CE is the realization of this idea.

For Sculpt users, the discovery starts at the '+' menu. In contrast to Sculpt
VC where the menu offered a rather long list of components to choose from, the
menu now offers nothing to be excited about.

[image sculpt_ce_menu]

However, at the very bottom, there is a new menu entry "Depot ...", which
leads to a sub menu with a list of enabled software providers. If connected to
the network, it also shows an entry named "Selection ...".

[image sculpt_ce_menu_depot]

The "Selection" sub menu allows the user to enable software providers.

[image sculpt_ce_selection]

When clicking on one of the checkboxes, the package index of the provider is
downloaded and the checkbox is highlighted. In the example, "nfeske" is
already enabled.

By clicking on the top-left triangle, one can always go one menu up. Back in
the depot menu, selecting a software provider will now display the index of
available packages. When selecting a new package, it can be installed via a
single click:

[image sculpt_ce_install]

Once the package is installed, the menu takes the user to a dialog for
integrating the package as a new component into the running Sculpt system. For
each resource required by the package, the user can decide how to connect it.
For example, the file system to be mounted at _/config/_ of a fresh
noux-system instance can be routed to any file system service the user wishes.
The noux-system won't know which file system is selected. It will just work
with it.

[image sculpt_ce_routes]

As soon as all routes are defined, the dialog presents a button for adding the
component to the system.

Using this interactive work flow, the discovery of software and its
integration becomes a rather playful process.

To make a once composed system permanent, one can use the inspect window to
copy the _/config/managed/deploy_ file to the _config/19.02/_ directory of your
Genode partition. This way, the deployment configuration will take effect
immediately at boot time.

Genode 19.02 comes with Sculpt CE included. As usual, we will take a bit
of time following the release for thorough testing and refining before
announcing an updated disk image mid March. We would greatly appreciate
your feedback during this phase! For baking a fresh Sculpt image, please
refer to the
[https://genode.org/documentation/articles/sculpt-vc - documentation]
of Sculpt VC, but using the Git tag '19.02' instead of 'sculpt_vc'.


Announcing software packages
----------------------------

The community experience of Sculpt CE will ultimately depend on the
participation of software providers. To become listed in the selection dialog
mentioned above, you may consider including your public key and download
location at the Genode repository at
[https://github.com/genodelabs/genode/tree/master/depot - /depot/].

For the announcement of packages, a software provider can publish so-called
"index" files for a particular Sculpt version in the software provider's
depot. E.g., the index of packages supported on Sculpt 19.02 would be located
at _index/19.02_ within the depot. Like any other depot content, index files
are digitally signed. An example index for the software provider "nfeske"
would look as follows:

! <index>
!   <index name="GUI">
!     <pkg path="nfeske/pkg/sticks_blue_backdrop/2019-02-22"
!          info="default desktop background"/>
!     <pkg path="nfeske/pkg/themed_wm/2019-02-26"
!          info="ready-to-use window manager"/>
!   </index>
!   <pkg path="nfeske/pkg/nano3d/2019-02-22"
!        info="simple software-rendering demo"/>
! </index>

Each '<pkg>' node refers to a package with a concrete version and a short
description. By nesting '<index>' nodes, software categories can be defined.

Index files can be published like any other depot content using the
_depot/publish_ tool, which takes care about compressing and digitally signing
the published information:

! ./tool/depot/publish nfeske/index/19.02

To ease the updating of the index with current package versions, the
_sculpt.run_ script creates the _depot/index/<version>_ file from the input
found in _repos/gems/run/sculpt/index_. The latter file is void of any version
numbers.

For any questions about the process, please consult the Genode
[https://genode.org/community/mailing-lists - mailing list].


Showcase of a Java-based network appliance
##########################################

With OpenJDK in good shape (Section [Java]), we have created a Genode scenario
that demonstrates JVM's ability to execute well on embedded hardware. As
target platform, we choose an ARM (i.MX 6) based SoC with two integrated
network interface controllers. In the scenario, the Genode system boots
directly into a Java application, which in turn spawns two HTTP server
instances where each instance communicates through a dedicated NIC. Both
server instances run as one Java program.

[image java_nic_filter]

The Java application (a JAR file) is loaded from the board's SD card, and
therefore, can easily be replaced. If you are interested in Java and ARM SoC,
the full details and a step by step instruction can be found at our
[https://genodians.org/ssumpf/2019-02-27-java-19-02 - Genodians.org] site.


Genodians.org as a showcase of a Genode-based web appliance
###########################################################

[https://genodians.org - Genodians.org] is our take on a federated blogging
platform about Genode-related topics. It does not host the actual content
but rather aggregates content hosted elsewhere.

[image genodians]

The site periodically fetches content in the form of zip archives containing
raw text and PNG images, extracts the archives, and transforms the text into
HTML using a custom static site generator. The result of the transformation
process is served by the lighttpd web server.

This system is based on Genode and can be found here:

:Genodians.org repository:

  [https://github.com/genodelabs/genodians.org]

A few noteworthy technical points about the site:

* The periodic process of downloading, extracting, and transforming content
  is realized via the 'fetchurl', 'extract', and 'sequence' components.

* The textual content uses the markup of the
  [https://github.com/nfeske/gosh - GOSH]
  text processing tool, which is similar to
  [https://daringfireball.net/projects/markdown/ - Markdown].

* The custom static site generator consists of a plain makefile and a few GOSH
  style files. The makefile is executed within a noux instance, which is
  Genode's custom Unix runtime environment. It is re-spawned for each
  iteration. As GOSH is written in Tcl, the tclsh is used within the noux
  environment.

* The lighttpd web server uses a statically supplied SSL certificate.

* The most time-consuming part of creating Genodians.org was the CSS
  definition.

* The entire system image is about *8 MiB* in size. It includes the following
  ingredients:
  * Kernel (e.g., NOVA),
  * Basic Genode components such as init, NIC router, the VFS server,
  * Network driver (based on iPXE),
  * Linux TCP/IP stack as a library,
  * Curl, libssh, libssl, libcrypto, lighttpd
    (for downloading and serving content),
  * libarchive, zlib, liblzma (for extracting the downloaded content)
  * Noux, coreutils (stripped down), bash, GNU make, and tclsh (for
    transforming text into HTML)

More information about the site's inner working will be posted in a series
of articles - guess where? - at Genodians.org!


Base framework and OS-level infrastructure
##########################################

Removal of deprecated APIs
==========================

Almost three years ago -
with [https://genode.org/documentation/release-notes/16.05 - version 16.05] -
we started the transition to Genode's modern API. One year later - in
[https://genode.org/documentation/release-notes/17.05#Completed_component_transition_to_the_modern_API - version 17.05],
we announced the completion of this transition but we retained the deprecated
APIs to accommodate Genode users that picked up the new API only gradually.
With the current release, we finally drop the deprecated APIs along with a
couple of other legacies:

* The _base/timed_semaphore.h_ has been removed. In hindsight, officially
  providing this utility was a big mistake because it lured developers into
  a wrong direction. In fact, we found that there is no legitimate use of it
  when a component is designed in a clean way. If a component relies on a
  timed semaphore, it should better be redesigned. There are two noteworthy
  places where a timed semaphore is still used as a band-aid solution:
  the 'pthread_cond_wait' implementation of the libc, and DDE for rump
  kernels. Those places now host a private copy of the timed semaphore, but
  should ultimately be reworked.

* The header _base/printf.h_ has been removed along with the log back end
  for 'printf'. The 'Console' with the format-string parser is still there
  along with 'snprintf.h' because the latter is still used at a few places,
  most prominently the 'Connection' classes.

* The notion of a 'Ram_session' exists no more since the former RAM-session
  interface was merged into the PD-session interface in
  [https://genode.org/documentation/release-notes/16.05#Consolidation_of_core_s_SIGNAL__CAP__RM__and_PD_services - version 16.05].
  Still, the types were preserved (by typedefs to 'Pd_session') to keep up
  API compatibility. Those last traces of 'Ram_session' are gone now. The
  'Env::ram()' accessor returns the 'Ram_allocator' interface, which is a
  subset of the 'Pd_session' interface.

* The use of the global 'Genode::env()' accessor function is not possible
  anymore.

* The old 'Child_policy::resolve_session_request' interface that returned
  a 'Service' instead of a 'Route' has been removed.

* Boolean accessor methods are no longer prefixed with 'is_'. E.g., instead
  of 'is_valid()', use 'valid()'.

* All connection constructors need the 'Env' as argument.

* The 'Reporter' constructor needs an 'Env' argument now because the
  reporter creates a report connection.

* The old notion of 'Signal_dispatcher' is gone. For receiving
  asynchronous notifications, the 'Signal_handler' interface must be used.

* Transitional headers like _os/server.h_, _cap_session/_,
  _volatile_object.h_, _os/attached*_dataspace.h_, and
  _signal_rpc_dispatcher.h_ have been removed.

* The distinction between 'Thread_state' and 'Thread_state_base' does
  not exist anymore. Only 'Thread_state' prevails.

* The header _cpu_thread/capability.h_ along with the type definition of
  'Cpu_thread_capability' has been removed. Use the type
  'Thread_capability' defined in cpu_session/cpu_session.h instead.

* The _os/ram_session_guard.h_ has been removed.
  Use 'Constrained_ram_allocator' provided by _base/ram_allocator.h_ instead.


Source-tree reorganization
==========================

Timer moved from os to base repository
--------------------------------------

Traditionally, the user-level timer was hosted at the os repository at
_drivers/timer/_. However, since the timer and timeout handling have become
part of the base library (the dynamic linker), the component naturally belongs
to the base repository. It is now located at _base/src/timer/_ and
_base-<kernel>/src/timer/_ respectively.

Note that this change affects include paths for the former
_include/os/timer/_, _include/os/alarm.h_, and _include/os/duration.h_
headers. Those can now be found in _include/base/_.


Consistent naming of block components
-------------------------------------

Regarding the naming of files and APIs, Genode follows the convention of
avoiding abbreviations. Most components follow this convention, with the block
servers being the exception to the rule. Those were named "part_blk" or
"rom_blk". With the current release, we removed this inconsistency by renaming
those offenders, changing "blk" to "block". Closely related, abbreviations
like "cli" and "srv" have been replaced by "client" and "server".


Improved API safety
===================

XML-parsing API
---------------

Genode consistently uses XML for component configurations and for reports
generated by components. The latter are often consumed by other components.
This puts the XML parser into a prominent position. Genode's XML parser
comes in the form of the 'Xml_node' class. Since it was introduced before the
age of modern C++, it offers several risky "C-ish" methods, in particular
accessors that return pointers, raising memory-safety concerns. To promote a
safe programming style, the following parts of the interface are subject to
change now:

* The 'Xml_node::addr', 'Xml_node::content_addr', and 'Xml_node::content_base'
  accessors will be removed because it is all too easy to store the returned
  pointers and forget about the lifetime of the originating 'Xml_node' object.

  Fortunately, in practice, those methods are rarely used because information
  is typically represented in attributes, not as node content. However, to
  still support the access to the raw content, the new
  'Xml_node::with_raw_node', 'Xml_node::with_raw_content', and
  'Xml_attribute::with_raw_value' methods call a functor taking the raw byte
  buffer and size as arguments. This way, the lifetime of the pointer is
  naturally bound to the scope of the functor.

* The new 'with_sub_node' method calls a functor with the specified
  sub node as argument and thereby reduces the need for the traditional
  'Xml_node::sub_node' method, which returns an 'Xml_node'.
  The latter is risky because an 'Xml_node' contains a pointer to the actual
  data. In contrast, the lifetime of the 'Xml_node' processed via the new
  'Xml_node::with_sub_node' is naturally bound to the scope of the passed
  functor.

* The 'Xml_attribute::value' and 'Xml_node::value' methods now take an
  argument of type 'T &out' instead of 'T *out', which eliminates the
  uncertainty of a possible nullptr argument.

The original interface will still be available for a while but it will
eventually be removed.


Simplified session-policy handling
----------------------------------

Most server components make use of the 'Session_policy' utility for selecting
a client policy depending on the session label. However, the pattern of its
use remained a bit inconsistent across components, in particular the handling
of the case where no policy could be found. Some components outright
denied the session where others implemented a fallback to a built-in default
policy. This inconsistency is now removed.

Following the principle of deny-by-default the absence of a matching policy
denies the session request. Since the 'Session_policy::No_policy_defined'
exception is a typedef to the 'Genode::Service_denied' exception, a server
does not need to explicitly handle it, which simplifies the implementation.
With this change, the 'No_policy_defined' case is always an error case. Hence,
the new version of 'Session_policy' prints a error message, which relieves the
server developer from implementing diagnostics in the server code.

As a consequence of this change, scenarios that used to rely on the
policy-fallback approach of some servers - notably the NIC bridge, window
manager, the window decorators - need a slight adaption: To enable the
fallback to a default policy, a '<default-policy>' node must be explicitly
specified in the server's configuration.


Removed pointers from Genode::Fifo interface
--------------------------------------------

To make the use of the 'Genode::Fifo' data structure more safe, all methods
that return pointers have been replaced by methods that call a functor with
a reference as argument.


New server-side block-request stream API
----------------------------------------

The current block-component API (_os/include/block/_) was designed at a time
long before Genode's modern component API was introduced. Back then, the use
of blocking calls was prevalent. Today, we design components to work
asynchronously. The original block-server API was successively enhanced to
allow the implementation of asynchronous block servers but it remained "upside
down" while growing more complicated than it should be.

To simplify the implementation and verification of block servers, the current
release introduces a modern API that will eventually replace the original
block-component API. The new API is called *block-request stream* and can be
found at
[https://github.com/genodelabs/genode/blob/master/repos/os/include/block/request_stream.h - os/include/block/request_stream.h].
It is designed with the following considerations:

* It anticipates the asynchronous operation of block servers by default.
  Using the new API, such servers - in particular block-device drivers - can
  be implemented as state machines triggered by client requests and device
  interrupts.

* It reinforces the memory safety of the server code by not returning any
  pointers or references.

* It relieves the server developers from handling special cases (like a
  congested acknowledgement queue) while being flexible enough to accommodate
  different categories of components like drivers, resource multiplexers
  (part_block), and bump-in-the-wire components in a natural way.

* It naturally supports the batching of requests as well as zero-copy
  (device DMA directly into the client's communication buffer).

The use of the new API is illustrated by the artificial test at
[https://github.com/genodelabs/genode/blob/master/repos/os/src/test/block_request_stream/main.cc - os/src/test/block_request_stream/].
We plan to successively migrate all existing block servers to this new API
and will remove the traditional block-component API eventually.


GUI stack
=========

Motivated by our work on Sculpt as described in Section
[Sculpt OS as a community experience (CE)], Genode's GUI stack received
the following improvements:


Window management
~~~~~~~~~~~~~~~~~

To improve the visual appearance of Sculpt's administrative GUI, the *themed*
*decorator* was enhanced with an option to disable decorations based on the
window label. By setting the 'decoration' attribute of a '<policy>' node to
"no", matching windows appear without any border, which is desirable for
Sculpt's component graph.

Furthermore, the themed decorator accepts the '<policy>' attribute
'motion=<number>'. The default value is 0. If a value higher than 0 is
specified, window-geometry changes are applied as an animation where the
<number> denotes the number of animation steps. This feature is used for
smoothing the placement of Sculpt's component graph.

The *motif* *decorator* - which is a nice alternative to the themed decorator -
is now giving visual feedback to mouse clicks. For example, while the user
drags a window by clicking on the window title, the title bar appears as
pressed, which creates an improved sense of responsiveness.


Unified shape-report routing
----------------------------

Applications propagate custom mouse-cursor shapes by issuing "shape" reports
towards the pointer component. The pointer component correlates the session
labels of the incoming shape reports with the label of nitpicker's currently
hovered client. Hence, an application's shape report session should take the
same route as its nitpicker session.

The presence of the window manager as an intermediary of the nitpicker session
breaks this rule. Consequently, rather awkward label-rewriting magic was
required when routing shape reports originating from windowed applications. To
make the shape reporting more natural, the window manager has become able to
proxy shape reports on behalf of its clients. When routing a shape through the
window manager, the labels of both the nitpicker sessions as well as the shape
report sessions contain the intermediary "wm ->" part.


Unicode support for the graphical terminal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The terminal has been changed to represent characters as 16-bit codepoints
internally. It thereby became able to display a much larger variety of
international characters when using a suitable font. Unicodes are sent through
the terminal session via bursts of UTF-8 bytes now.

As a collateral change, the generic 'Codepoint' class became printable via
Genode's 'Output' interface. This way, a codepoint can easily be serialized
into UTF-8 bytes.


Programming languages
#####################

Ada and SPARK
=============

_The work described within this section was contributed by_
_[https://componolit.com - Componolit]. Thanks to Alexander Senier_
_and Johannes Kliemann for the fantastic collaboration!_

The integration of SPARK/Ada programs was improved greatly and the Ada runtime
was renamed to 'spark'. This emphasizes its main purpose: trusted components
that can be formally verified. A more feature-rich runtime based on 'libc' was
added to genode-world under the name 'ada'.

Build system integration
------------------------

Up until now, the (deprecated) 'gnatmake' tool was used to build Ada object
files. This was unfavorable for two reasons: First, multiple invocations of
gnatmake would sporadically corrupt the compiler-generated Ada linker files
('.ali') and break parallel builds. Second, Ada dependency information did not
get propagated into Genode's build system such that certain source changes
failed to trigger a rebuild.

For these reasons the 'gnatmake' tool has been dropped in favor of regular
compiler calls as done for all other languages. To facilitate consistent
rebuilds on source-code changes, the
[https://github.com/Componolit/ali2dep - ali2dep] tool was created. From an
'.ali' file, it produces '.d' files suitable for direct inclusion into
Genode's build system.

Until the integration into the toolchain, 'ali2dep' support needs to be
enabled through the 'CUSTOM_ALI2DEP' variable (absolute path or command name
if the command is in 'PATH'). By default, a warning about the absence of the
tool is emitted and dependency information is not generated. You can add this
variable to the 'etc/tools.conf' of your build directory as follows:

! CUSTOM_ALI2DEP = /path/to/ali2dep

Elaboration code
----------------

Previously, Ada programs that required elaboration code to be run were
unsupported on Genode. With this release, Ada programs are bound using
'gnatbind', which results in elaboration code being generated. An additional
benefit comes in the form of proper error messages at compile time if, for
example, source code is missing or outdated.

To run an Ada main program with elaboration, calls to 'adainit()' and
'adafinal()', generated by the binder, need to be added to your
component-construction code:

! extern "C" void _ada_main(void);
! extern "C" void adainit();
! extern "C" void adafinal();
!
! void Component::construct(Genode::Env &env)
! {
!    adainit();
!    _ada_main();
!    adafinal();
!    env.parent().exit(0);
! }

Note, that the name of the Ada main program ('_ada_main()') in this example
depends on the name of your main procedure.

Debug output
------------

Support for 'GNAT.IO' was added to the runtime. 'GNAT.IO' is a stripped-down
text I/O facility, which we map to a terminal session on Genode. Only output
is supported at the moment. A pointer to a terminal session has to be provided
to the ADA runtime in order to use 'GNAT.IO'. Please refer to
_repos/libports/src/test/gnatio/_ as an example.

Unit testing
------------

To facilitate test-driven development of Ada components, the
[https://www.adacore.com/documentation/aunit-cookbook - AUnit] unit testing
framework was ported to Genode. It is located in the genode-world repository
whereas a usage example can be found at 'src/test/aunit'. Note that the full
Ada runtime ('ada') is required as the framework uses features not present in
the SPARK runtime.


Java
====

Since Genode release
[https://genode.org/documentation/release-notes/18.11#Java_language_runtime - 18.11],
we continued our effort to enable the just-in-time (JIT) compiler for OpenJDK.
We are happy to announce that we were able to achieve this goal. The JIT
compiler is now enabled as default for both x86 (64 bit) and ARM (32 bit),
which significantly improves the performance of the Java virtual machine for
these architectures.

Additionally, we even further improved JVM's performance by taking advantage
of more aggressive compiler optimizations. This triggered some unidentified
bugs and led to a greatly enhanced stability of OpenJDK.

For a small hello world example we offer a simple run script:

! make run/java

For a more complex scenario please refer to Section
[Showcase of a Java-based network appliance].


Nim
===

Support for Nim has been removed from the Genode build system to encourage
building Nim components out-of-tree using the Nimble package manager.
The compatibility of the base system with the Nim runtime will be monitored
and improved regardless of this change.


OCaml
=====

A proof-of-concept port of the OCaml bytecode interpreter has been placed
in the world repository. This allows simple programs that are compiled to the
bytecode instructions to be executed and is a first step in supporting the
OCaml language. This interpreter does not yet include the standard library.
Therefore only language primitives are available. Porting the standard library
appears to simply be a matter of defining a build process. The greatest
hurdle to porting existing OCaml applications would seem to be finding a path
into the workflow of the OPAM package tooling.


Libraries and applications
##########################

New utility for taking screenshots
==================================

The flif_caputure screenshot utility has been added to the world repository.
This utility implements a framebuffer and input service which it proxies to
its parent. When the utility observes the *PrtSc* key, it captures the content
of the framebuffer and writes it to the file system in the FLIF image format,
FLIF being chosen primarily for its uncomplicated API. To use the utility in
practice, the common case would be to run it as a client of the default window
manager with a second window manager stack running as a client of the capture
utility. This allows capture behavior and scope to remain simple and explicit.

The background story behind the tool is covered by a dedicated
[https://genodians.org/ehmry/2019-01-31-flif_capture - posting] at Genodians.org.


Growing use of the Genode-World repository
==========================================

The [https://github.com/genodelabs/genode-world - Genode-World] repository
contains software that is not strictly part of the official Genode OS
framework but rather supplemental. In particular, it contains ports of
3rd-party software to Genode. The pool of ported software is steadily growing,
which moves the world repository more and more into the spotlight of Genode
users. For example, among a variety of games and experimental components, our
port of OpenJDK ([Java]) is also hosted there. To acknowledge the growing
importance of the world repository, we added the building of all world depot
archives to our nightly build tests.

With this baseline of quality assurance in place, it was a good time to move
supplemental software such as Dosbox, FUSE, libav, libSDL, and its companion
libraries from the Genode repository to the Genode-World repository. Speaking
of libSDL, as part of the curation of the world content, the library back end
of libSDL has been changed to the direct use of the nitpicker session
interface instead of the lower-level framebuffer and input interfaces. Thanks
to this change, many scenarios could be greatly simplified, in particular
packages designated for the use in Sculpt OS.


Updated or removed 3rd-party software
=====================================

The following 3rd-party software received an update:

* OpenSSL updated to version 1.0.2q with 'SSL_CONF_*' enabled,
  as needed by lighttpd's mod_openssl.

* Lighttpd updated to version 1.4.52, with TLS enabled.

* libpng updated to version 1.6.36

* jbig2dec updated to version 0.15


Removal of VirtualBox 4
-----------------------

All regular users of Genode's VirtualBox port migrated to version 5 a long
time ago. Version 4 was still maintained because this is the only version
supported on the Muen separation kernel. However, since the focus of the Muen
developers recently moved towards the use of nested virtualization, our
version of VirtualBox 4 is no longer vital for Muen. So we could remove it.


Platforms
#########

Board support for i.MX6 Quad Sabrelite and Nitrogen6 SoloX
==========================================================

In 2018, we extended our device-driver support for NXP i.MX 5 and 6 based ARM
platforms. This year, we continue our commitment to this platform with
additional support for the NXP reference board i.MX6 Quad Sabrelite and the
Nitrogen6 SoloX, which features dual Gigabit Ethernet.


Resizeable virtual framebuffer on Linux
=======================================

When executing Genode on Linux, we use a libSDL-based pseudo driver for
running graphical scenarios. This *fb_sdl* server has now been enhanced with
the ability to resize the SDL window. Such a resize event is translated into
Genode's framebuffer resize protocol. Thereby, the resizing of the host window
looks like a mode change to Genode's GUI stack. This greatly eases the testing
of the mode-change handling of components like the nitpicker GUI server.


Tooling and build system
########################

Enforced 'override' annotations
-------------------------------

The '-Wsuggest-override' warning complains about implementations of virtual
functions that lack the override keyword. If the implementation of a virtual
method is marked as 'override' the compiler checks for a matching virtual
method in the base class. If there is no such method, the implementation
unexpectedly diverged from the interface.

An interface may change over time, which is especially troublesome when it
contains a default implementation of a virtual method. Without 'override'
annotations, the compiler will silently add the outdated implementation of the
derived class as an overload of the interface's default implementation, which
introduces a subtle but potentially serious bug.

To rule out such bugs in the future, we made 'override' annotations mandatory
when using the default strict warning level.


Generalized use of the depot by run scripts
-------------------------------------------

With more and more run scripts using archives out of Genode's depot, we gained
experience with typical usage patterns. In particular, we found the universal
use of the configurable depot user preferable over the hard-wiring of
'genodelabs'. Hence the 'depot_user' function has become a built-in function
of the run tool.


Repeat mode for the depot-autopilot test environment
----------------------------------------------------

The _depot_autopilot.run_ script now supports the environment variable
'TEST_REPEAT' with the possible values 'until_forever' and 'until_failed'.
When specified, the tests are run in a loop. The latter argument is
particularly useful for reproducing sporadic errors.


New run script to execute a single test w/o the depot
-----------------------------------------------------

The new _os/run/test.run_ script allows for the quick execution of an
individual test from the build directory while side-stepping the depot.
It expects a 'PKG' variable specifying the test package. E.g.,

! make run/test KERNEL=nova PKG=test-xml_node

Note that it does not cover all test packages right now.
The tool and its limitations are explained in more detail by a dedicated
[https://genodians.org/nfeske/2019-02-05-shortcut-for-testing - posting]
at Genodians.org.


Support for undefined-behavior sanitizer
----------------------------------------

The
[https://developers.redhat.com/blog/2014/10/16/gcc-undefined-behavior-sanitizer-ubsan/ - UndefinedBehaviorSanitizer]
(UBSan), also described in the
[https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html - GCC documentation],
can detect undefined behavior while a program is running.

With the current release, this diagnostic feature of GCC becomes available for
analyzing Genode components. By specifying 'SANITIZE_UNDEFINED = yes' in a
'target.mk' file, the '-fsanitize=undefined' compiler flag is enabled and the
program is linked with libubsan and libsanitizer_common. The program has to
call 'env.exec_static_constructors()' and 'sanitizer_init(env)' upon startup
to initialize the sanitizer libraries. Whenever undefined behavior is detected
while the program is running, a "runtime error:" message including the source
code location of the error is printed to the log.