[Beowulf] Seg Fault with pvm_upkstr() and Linux.

Vincent Diepeveen diep at xs4all.nl
Wed Mar 16 16:36:48 EST 2005


At 09:30 AM 3/16/2005 -0500, Robert G. Brown wrote:
>On Tue, 15 Mar 2005, Josh Zamor wrote:

>I assume that you've experimented and have no difficulty returning and
>unpacking ordinary ints, strings, or raw data blocks with PVM.  If so
>you probably aren't making a pointer error on the master server side,
>although it never hurts to check.

I wouldn't count on it being bugfree; usually it takes a long time before
people discover the beautiful 'sizeof' command in C and as we know that
will give back '4' in a lot of cases at his 32 bits XP and '8' at the 64
bits g4.

For example but not limited to:
  printf("sizeof(long) = %i\n",(int)sizeof(long));

Also integer is not safe, as standards do not force it to be 32 bits.

Then there is the usual casting problem and compare problem. Notorious is
this compare:
  int a; unsigned int b;

if( b == a ) // result undefined

Odds for bugs in the program are like 99.99%

>If you want other eyes on your actual code (might be useful if it is
>indeed programmer error) please post.
>
>   rgb
>
>-- 
>Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
>Duke University Dept. of Physics, Box 90305
>Durham, N.C. 27708-0305
>Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu
>
>
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