[tex-live] building from source

[Karl Berry]

    ifdef __USE_GNU:

Ok, so the question is why and how is __USE_GNU being defined.
It's not explicitly in the TeX sources anywhere.

djh, if you could add -dD to the gcc line for one of the files, you will
get output which is the results of preprocessing with all the
#define's intermixed, and can look for __USE_GNU there.  Also, it would
probably be worth running
  gcc -E -dM - </dev/null
and see if it is predefined.  (If so, I think -U__USE_GNU would solve
the problem.)

Apparently __USE_GNU does not get defined on (GNU:)/Linux, because this
error isn't reported there.  (And I see the declaration in
/usr/include/stdio.h, likewise #ifdef'd.)

Thanks,
Karl