Re: [ECOS] bug allert, variable alignment problem in ecos

[Larice Robert <larice@vidisys.de>]

Hello Stephen,

  how did you deal with this, did you stop the project, did you find
  a solution, or did you just live with the linker lottery.
  most of the time you wont notice the problem, because most global objects
  are aligned to 4 byte. so if there are just few in-between, you have
  a good chance to be lucky.

  actually the problem i've described is not C++ specific. though
  the want to allocate space for some class object, and the want
  to avoid constructor calling, has led to some
     char space[sizeof(class ..)];
  in the ecos tree, which is another manifestation of the alignment problem.

  to extend your aside, for me too, the decision to use C++ for the
    bit-tiddling internals of an embedded realtime os is a bit
    unexpected. but with great care can be done, and has merits too.

  anyway, i've sent a patch for almost 200 dangerous global variables
  to ecos-patches. (though most of them are in some test directories, and
  thus of minor significance. those will even be helpfull to get
  accustomed with the debugger)

Robert Larice

> Yes.  We saw the problem in debugging eCos on a MIPS32 processor and it 
> drove us crazy.  It showed up especially in threads structures as these 
> are shared between C and C++ code, which apparently have different 
> alignment rules.
> 
> As an aside, I'm a dyed in the wool C programmer, and find C++ a miserable 
> language.  Why would anyone mix C and C++ within an operating system?  Of 
> course, I use vi as I find emacs incomprehensible, which may indicate 
> something about my sensibilities -- or merely my abilities...  8-)
> 
> Stephen P. Morgan

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