Installed gcc 4.2.1. Discovered that we have 16-byte stack tax^Walignment enforced on us now. :(

Rob Landley rob at landley.net
Thu Jul 26 01:05:01 UTC 2007


On Wednesday 25 July 2007 7:36:26 pm Dave Dodge wrote:
> On Wed, Jul 25, 2007 at 08:00:31PM -0400, Rob Landley wrote:
> > And what am I supposed to think about that makes it necessary?
>
> I haven't paid close attention but I seem to recall this being
> mentioned several times on the ffmpeg lists (in which the code does
> use a lot of sse/mmx).  I think a recent version of gcc _didn't_ do
> this alignment for some reason and it broke things badly.
>
> If the C library doesn't require this alignment internally then you
> can presumably shut it off for function calls within the library.  But
> any possible paths back into the user application (such as qsort() or
> bsearch()) may need to maintain the alignment.

I do crazy things like try to build i486 versions of Linux with no floating 
point, so I'm glad it can be switched off.  (I tend to find out what a given 
combination of programs can and can't do experimentally, by breaking it.)

>                                                   -Dave Dodge

Rob

-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.



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