Loading object files into executing programs [users of PADPowell's code plse read]

[Michael W. Herman]

Check net.sources from about 6 months ago.  PADPowell at wateng
had  posted  some code he developed (twice actually). I have
an improved version of  his  code  that  I'm  not  ready  to
distribute just yet.

On the subject of efficiency ...

I would like to know if anyone else is using Pat's code  and
has  attempted  to  speed up the dynamic loading.  My quasi-
quantitative analysis shows it takes from 10-40  seconds  of
elapsed  time to  dynamically load ~10 Kbytes of code image.
Of the total, about 2 seconds of elapsed time is  needed  to
invoke  *ld*  (regardless  of  whether you use *system()* or
*vfork* and *execv*).  Most of the rest of time is spent  in
*ld*  itself.  About 25% of this time is spent in the *read*
system call reading libraries (which, in my application, are
quite large (~500 Kbytes) and yes, compiled with cc -g ...).
*ld* seems to be doing a lot  of  optimization  of  the  i/o
already so I don't expect to be able to speed *ld* up.

However, I expect things to speed up quite a bit when I drop
-g.

I would like to try eliminating  the  2  seconds  needed  to
invoke *ld* by loading it into the program at "compile-time"
and calling it directly as an  ordinary  C  function  (or  I
suppose  I  really  should be dynamically loading it  ;-) ).
This would involve turning the *ld* program into a  function
(mostly  just  a  name  change  and the problem compile-time
initialization of static variables).   If  anyone  has  done
this, plse let me know.

On the subject of *dbx* ...

At the moment a lot of my code has been compiled with -g  to
leave  the  extra  symbol table info lying around for *dbx*.
It would be  nice  to  be  able  to  have  this  information
preserved in the dynamically loaded code as well.  I haven't
had any luck in trying to achieve this.  Apparently,  it  is
the  C  compiler  that  causes  this  info to remain when an
executable code image is created by *ld* and *ld* is passive
in  this  regard  (It  just  does  the loading including the
forced loading of -lg (because it  really  just  a  .o  file
masquerading as a .a library).) I've tried using *cc -A ...*
instead of *ld -A ...* to create the code image  to  be  but
get all sorts of "multiply defined" msgs from *ld*.

Plse let me know if you have any suggestions that might help
solve this last point.


Michael Herman
Computer Graphics Laboratory
Department of Computer Science
University of Waterloo
Waterloo, Ontario, Canada  N2L 3G1

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