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Diving Into GCC: OpenBSD and m88k

Posted by michael on from the swimming-pool-filled-with-double-edged-razor-blades dept.

BSD Forums writes "This OnLamp article by Miod Vallat describes how the m88k-specific backend of the GNU C compiler, gcc, was fixed, from the discovery and analysis of the problems to the real fixing work. Since it started with almost zero gcc internals knowledge, it should be understandable by anyone able to read C code, and proves that diving into gcc is not as hard as one could imagine."

2 of 167 comments (clear)

  1. Oh, catch the hell up. by devphil · · Score: 5, Informative


    I love and trust OpenBSD, I really do. Nothing is more secure for a firewall or external server. But if they're not going to use the maintained versions of programs, I have little sympathy for their troubles; these situations have a big "for masochistic hobbyists only" sign all over them.

    Unfortunately, gcc, by design, will never inline functions (even if explicitly requested) at -O0. The non-return point had been crossed: gcc had to be fixed.
    [...]
    After compiling gcc 2.95 with gcc 2.8,

    This is where I stopped reading. This has been "fixed" for a long, long time. If the GCC port is too old and has gone unmaintained, then just maybe it's time to throw it out and start over. The 2.x compiler is dead and buried. Nobody's interested in maintaining it. Patches for it are not going to be accepted.

    For those interested in why certain kernel code has to be inlined (under any kernel): early in the boot process, you can't necessarily call functions. There's not enough of a sane stack or relocatable memory. Linux got bitten by this many times, relying on undefined behavior in particular versions of GCC. The choices are either to write one long hairy function, or force inlining.

    GCC introduced always_inline for just those situations. Of course, if the users are still trying to get 2.x from years back to work, they won't be able to use it...

    --
    You cannot apply a technological solution to a sociological problem. (Edwards' Law)
  2. Re:hard by Anonymous Coward · · Score: 5, Informative

    So why is it Apple can't make a real processor-specific-optimized version of GCC for Mac OS X?

    There is no advantage to deviating away from GCC too much because you miss important optimizations in the main GCC trunk. BTW, Apple does have its own GCC tree fine-tuned for Mac OS X - they'd virtually have to as an OS vendor (think device drivers written in GCC 2.95 versus GCC 3.2). Apple would love to merge it back into the GCC main (complete with Objective C++), but the GCC project only accepts very conservative patches generally.