Confusing behaviour from gcc and ld with --as-needed

[Mike Hearn]

Hi,

[mike@littlegreen libexec]$ gcc -o vfolder-magic vfolder-magic.c -Wl,--as-needed `xml-config --cflags --libs`
[mike@littlegreen libexec]$ needed vfolder-magic
  NEEDED      libxml.so.1
  NEEDED      libc.so.6
[mike@littlegreen libexec]$ gcc -o vfolder-magic -Wl,--as-needed `xml-config --cflags --libs` vfolder-magic.c
[mike@littlegreen libexec]$ needed vfolder-magic
  NEEDED      libc.so.6


The only difference between the two GCC invocations is the position 
of the source file on the command line. Yet, the output is different.

I'm sure there is some good reason for this, but I can't see what it 
might be. Is there some behaviour of GCC or GNU ld that I have 
overlooked here?

thanks -mike