Add *-helenos-* target to GCC

[Vojtech Horky]

Patch GCC compiler to support a truly native *-helenos-* target.

Details

The GCC compiler was ported to HelenOS during 2013. The porting effort concentrated on running the GCC somehow in HelenOS and there was no emphasis on patching GCC to look as a native compiler. Thus, the user still needs to add -nostdlib and ​similar flags to it to compile anything in HelenOS.

The goal of this project is to add a *-helenos-* target to GCC that would target the Linux ABI but would use HelenOS-specific directories or predefined macros. Also, the ported GCC is rather old (4.6.3) and shall be updated to the newest version (this includes the need to add rudimentary support for C++ in HelenOS).

Follows an incomplete list of some of the features that needs to be covered

• update to newest GCC
• add support for C++ to HelenOS
• add HelenOS specific defines such as __LE__ or __32_BITS__
• get rid of Linux defines such as __unix__
• use HelenOS include directory /inc instead of all the /usr/something that are used in Linux
• use proper linker script

It would very nice to add a custom HelenOS -posix switch for building POSIX applications opposed to native HelenOS ones.

What Gains and Benefits will this bring?

One of the strategic goals for HelenOS is becoming self-hosting. Since most of the HelenOS code is written in C, having a portable, full-fledged native C compiler is a prerequisite to reaching this goal. Using the same compiler for cross-compilation and building HelenOS from itself is also a benefit of its own. This particular task will improve the usability of GCC when run inside HelenOS.

Difficulty

Easy to Medium. Once the student becomes acquainted with the organization of GCC source tree, the patches would be rather straightforward. Prospective applicants shall consider proposing this one together with Bazaar port.

Required skills

A successful applicant will have good skills of programming in the C language and the ability to survive in a non-standard non-POSIX application environment. The applicant should also be familiar with the basic concepts behind compilers and the build toolchain.

Documentation

• DeveloperDocs
• ​GCC, The GNU Compiler Collection
• ​OSDev: OS Specific Toolchain
• Adding basic support for *-helenos-* target to the toolchain
• ​Blog ​posts ​about ​GCC ​porting
• ​Blog ​posts about helper scripts for porting software to HelenOS
• GCC internals
  • ​Controlling the Compilation Driver
  • ​Spec file details
  • ​How to inhibit default library paths

Possible mentors

HelenOS Core Team, Vojtech Horky

[Jiří Zárevúcky]

Working on this.

[Jakub Jermář]

Can this be closed now?

[Jakub Jermář]

Fixed in commit bbe5e34956da986df4d32357c697e539e8cfec0d