Fork us on GitHub Follow us on Facebook Follow us on Twitter

Version 60 (modified by Jiri Svoboda, 2 years ago) (diff)

ISO C conformance notes

Release Notes for HelenOS mainline

Note: This document is a draft describing a future HelenOS release and is subject to change. The software described here has not been released yet. To get these latest and greatest features now, check out our Git master. (But you will also get the latest bugs).

HelenOS 0.7.2 (Boosted Effort) was released on date.

This document contains a summary of changes made to HelenOS since release 0.7.1.

Special Notes for this Release

Features Introduced in This Release


  • Integrate support for the Sycek C style checker into the build system. Sycek helps to make HelenOS source code nice and tidy, and in some cases can even spot real bugs. Run either with make ccheck or as part of make check.
  • Basic build tests executed with each commit via Travis CI


  • Most of the work on the kernel focused on improving the capability system:
    • IPC calls in userspace are no longer represented by the so-called call ID's or hashes which were essentially leaked kernel addresses. Instead they are now managed using task-local call capability handles.
    • Improved life-cycle management of kernel objects, especially phones, and capabilities. When allocating a new capability the kernel does no longer attempt to reclaim an unused allocated one. Instead, each kernel object is now deallocated immediately when its reference count drops to zero. For phones, this now newly means that the phone has no active calls.
    • Capability handles are now type-safe so that it is no longer possible to confuse eg. a phone capability handle with a call capability handle. Or a capability handle with an integer.
  • On amd64 and ia32 architectures, the kernel now survives a deferred #DB exception during a system call.
  • Generalized the kernel ns16550 driver to work with more chips. Some UART controllers are compatible with 16550A, but have more spacing between registers. In particular, ARMADA 385, which is the basis of Turris Omnia router, has a compatible UART with 32-bit registers instead of 8-bit.
  • Instead of using plain malloc, the slab allocator now uses a dedicated cache for allocating the per-CPU magazines of caches.

Services and Drivers

  • USB 3 support
    • General overhaul of the existing USB framework
    • New host controller driver has been implemented to control various xHC models (among others, NEC Renesas uPD720200)
    • Isochronous data transfer mode
    • Support for explicit USB device removal
    • USB tablet driver
  • Unify all the different character device interfaces accrued over the years and use only the one provided by io/chardev.h and io/chardev_srv.h
  • Move ADB keyboard and mouse support from the input server into separate drivers
  • Finish DDF conversions of ski, sun4u and msim console drivers
  • Added new NIC driver for virtio-net.
  • The nic command now works with the ne2k driver too
  • FIXME Volume management improvements

File Systems

  • TMPFS is now populated from a TAR archive when used as a root file system



  • Fix text editor screen being broken when editing files with long names


  • Added libvirtio to aid writing VIRTIO device drivers.
  • The async framework API has been streamlined and the abstraction no longer leaks the internals of the low-level IPC mechanism. The async framework server calls no longer require the call capability handle and the pointer to the IPC call structure serves as an universal identifier of the given IPC call on the server side.
  • Improved ISO C comformance
    • Some ISO C symbols that were previously only available through libposix now moved to libc
    • In many cases improved implementation
    • scanf family, temporary file functions from stdio.h, (at)exit family from stdlib.h, etc.
  • C++14 Runtime support
    • C++ source files are compiled with -std=c++17 (which grants most, if not all, C++17 language features)
      • These files are detected by having .cpp, .cxx or .cc as their extension
    • Runtime:
      • RTTI (type_info and typeid, no dynamic_cast at the moment)
      • Thread-safe local static variable initialization
      • Global static variable initialization/destruction
      • No support for exceptions at the moment, though try/catch/throw are redefined and should not break code (inclusion of <__bits/trycatch.hpp> needed)
    • Standard library:
      • All containers except forward_list (some algorithms missing, such as sort() on list), including adaptors
      • Most of utilities
        • <type_traits>, <ratio> complete
        • <utility>, <tuple>, <memory>, <function>, <chrono>, <bitset> mostly complete
        • <scoped_allocator> not implemented
      • I/O library is complete, but does not throw and ignores localization
        • <locale> is defined, but is a stub (implementing it will add its functionality to I/O types)
      • Threading mostly complete, timed try_lock operations block, <future> only stub
      • Iterator traits and adaptors complete
      • Numerics have only <numeric> complete and <random> partially implemented (missing some distributions and adaptors)
      • Partial <algorithm> implementation
      • <regex> and <atomic> not implemented
      • <string> implemented, but wide strings are untested (missing wide string functions in libc)
      • C library header wrappers are only partially implemented because features are missing from libc
      • Types from diagnostics library (<exception>, <stdexcept>, <system_error>) are implemented, but exception handling does not work
  • Previously, HelenOS used negative error codes, which made it difficult to align with the ISO C standard which mandates that the error constants are positive. In this release we therefore switch the sign. A nice summary of this refactoring operation is provided here.


  • FIXME ELF loading changes
  • Headers with structures and their respective member offsets shared between C code and assembly are no longer generated from a YAML description, but are instead provided in a readily-usable header file and checked for consistency by the build system.
  • Userspace portions of HelenOS can now be built with undefined behavior sanitizer enabled, making it easier to detect certain kinds of problems.
  • The tools/ script used for sarting HelenOS in various emulators now accepts some new arguments:
    • -noxhci: The XHCI USB host controller is enabled by default. Use this switch to override.
    • -notablet: When used with QEMU, the USB tablet offers better user experience over plain USB or PS/2 mouse as the mouse cursor can seamlessly move between the guest window and the host. Use this option to disable.
    • -noserial: By default the serial output is enabled if supported by the configuration. This option overrides this.
    • -bigmem: Some configurations are memory hungry and need more memory. Use -bigmem to set maximum RAM size to 4GB.
    • -net virtio-net: Use this to enable the VIRTIO network inteface.

Regressions in This Release

  • For the list of regressions since the previous release, see this report.
  • Notable regressions

Fixed Logged Bugs & Enhancements

  • For the list of all logged defects fixed in this release, see this report.
  • For the list of all logged enhancements integrated in this release, see this report.

Known Bugs

  • For the list of known bugs still not fixed in this release, see this report.
  • For the list of all open tickets, see this report.