parsing getline var argument

[Joel E. Denny]

I am trying to understand GNU AWK's parser as it relates to an extension I 
am working on for Bison.  However, I don't use AWK often, so some of my 
questions may be naive.

I checked out GNU AWK from CVS and built it.  The most recent ChangeLog 
entry at the time was Sat Aug 11 22:48:11 2007.

I then ran:

  % ./gawk '{getline $4; print $4;}' > stdout
  line 1
  line 2
  % cat stdout
  line2

Recent releases of GAWK behave in the same way, but this behavior differs 
from /usr/bin/awk under Solaris 10:

  % /usr/bin/awk '{getline $4; print $4;}' > stdout
  line 1
  line 2
  % od -c stdout
  0000000  \n
  0000001

What is the correct behavior?  Is `getline $4;' a GNU extension?  Or is 
the behavior undefined here?

If CVS GAWK is correct, then how should it parse the following expression?

  getline $4*0;

In Makefile, I added -DGAWKDEBUG to CFLAGS.  I then rebuilt GAWK and ran:

  % ./gawk --parsedebug 'getline $4*0;'

>From the parser trace, I see that GAWK parses the expression as:

  (getline $4)*0;

For example:

  % ./gawk '{ print getline $4; print getline $4*0; }' > stdout
  line 1
  line 2
  line 3
  % cat stdout
  1
  0

However:

  % /usr/bin/awk '{ print getline $4; print getline $4*0; }' > stdout
  line 1
  line 2
  line 3
  % cat stdout
  1
  10

What behavior is correct?

Thanks.