From: John (I've got some bad news for you, sunshine) Mackin <john@vetsci.su.oz.au>
To: Byron Rakitzis <byron@archone.tamu.edu>
Cc: The rc Mailing List <rc@archone.tamu.edu>
Subject: really bad order of evaluation bug
Date: Wed, 29 Jan 1992 06:08:59 -0600 [thread overview]
Message-ID: <199201291936.423.rc.badas@vetsci.su.oz.au> (raw)
Byron,
I got your mail this morning but haven't had time to reply today, and I have
to get off and sleep soon. But before I do I thought I had better mail you
this one. I spent four hours tracking this down today -- sigh. I thought
I should copy it to the list since it's so very drastic.
The symptom here was that on one particular type of machine -- Sony News,
but the 68000 one, not the MIPS one -- redirection wasn't working right.
If you did
ls thisisntthere >xxxx >[2=1]
then the error message -- which was most definitely getting printed on
fd 2 -- came out _on the terminal_, and xxxx ended up with nothing in it.
This didn't happen on any other machine I had easy access to. Actually,
having found it, I'm really surprised that it isn't broken in more
places: perhaps it is and people just haven't noticed. This is an
order of evaluation bug in glom.c, which was introduced between 0.9
and 1.0 -- 1.0 has new code here and it has been broken ever since.
Here is the fix:
*** glom.c-BUG Wed Jan 29 18:42:34 1992
--- glom.c Wed Jan 29 18:41:48 1992
***************
*** 516,522 ****
}
words = words->u[0].p;
}
! return append(append(glom(words), last), glom(n->u[1].p));
case BACKQ:
return backq(n->u[0].p,n->u[1].p);
case CONCAT:
--- 516,523 ----
}
words = words->u[0].p;
}
! first = append(glom(words), last);
! return append(first, glom(n->u[1].p));
case BACKQ:
return backq(n->u[0].p,n->u[1].p);
case CONCAT:
I guess that either damn near every compiler out there evaluates
function arguments left-to-right (where _are_ the pcc-based ones
any more? :), or else the people who use right-to-left compilers
don't use `fancy' redirections....
I'll reply to your other mail tomorrow my time. Say 10-12 hours.
OK,
John.
reply other threads:[~1992-01-29 12:15 UTC|newest]
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