id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	field_blocks	field_dependson	field_seealso
654	C++ support	Vojtech Horky		"Implement support for C++ in HelenOS to allow compilation and execution of C++ programs.

 Details::
  Currently the only language that is fully supported for development of applications for HelenOS is plain C. While C is a good choice for kernel and low-level services, for more complex applications C++ might be a better choice. The goal of this ticket is to bring support for C++ to HelenOS, from toolchain installation to run-time support in HelenOS.
  [[br]][[br]]
  HelenOS toolchain script already installs a C++ compiler (`g++`). Still some minor changes might be needed (probably in the form of `configure` options).
  [[br]][[br]]
  Since all HelenOS components (kernel, userspace servers and utilities) are currently written in C, the build process compiles all source files with a C compiler. It would be necessary to add support for compilation of C++ programs, e.g. by automatic detection of `.cpp` files among the sources or by a manually specified flag.
  [[br]][[br]]
  Next step is adding the run-time support for C++. The C++ compiler expects that a system library implementats functions needed for the support of exceptions (namely support for stack unwinding) and run-time type identification. There are two options: port the GCC-provided libraries or write implementation from scratch. The first option would probably require extensive patching as HelenOS is a non-POSIX environment but it would bring a full-fledged support. On the other hand, rudimentary support can be written from scratch and extra functionality might be added later, in an on-demand manner.
  [[br]][[br]]
  Last step towards full C++ support is STL with `std::string`, containers and streams. Again, it is possible to write the library from scratch or port an existing solution.

 What Gains and Benefits will this bring?::
  The obvious benefit when this task is completed is the ability to execute C++ programs inside HelenOS. That would give HelenOS developers more flexibility in development of new utilities and servers as another language would be supported. By adding the C++ support it would also be possible to upgrade the GCC version we currently use inside HelenOS (i.e. not the cross-compiler but the native compiler available through Coastline), bringing HelenOS one-more step closer to being self-hosted.

 Difficulty::
  medium to high

 Required skills::
  A successful applicant will have good skills of programming in the C and C++ languages and the ability to survive in a non-standard non-POSIX application environment. Understanding of compiler internals would be beneficial. 

 Documentation::
   * DeveloperDocs
   * [[http://wiki.osdev.org/C%2B%2B|On C++ run-time support (OSDev wiki)]]
   * [[PortingSoftware|Porting software to HelenOS]]

 Possible mentors::
  HelenOS Core Team, Vojtech Horky
"	enhancement	closed	major	0.7.2	helenos/unspecified	mainline	fixed	gsoc16, gsoc17