question on include search path

[esp5 at rama dot comp dot pge dot com]

hey,

I was wondering - *exactly why* when you say:

gcc -print-search-dirs

does it only show 'install:', 'programs:', and 'libraries:' as search paths?
What about headers? If I say

#include <stdio.h>

I'd like to know which directories are being searched there, too...

Also - speaking of headers, why is it when I install gcc in a non-standard 
location, say /opt/install, that '/opt/install/include' is not included as 
a directory for constructs of the form:

#include <zlib.h> 

(?)

Are these bugs? It seems hard to believe that this is not there by design, but
I can't think of any possible advantage of not having this included


And come to think of it, why is there no:

LD_INCLUDE_PATH

or some such equivalent to add onto the list of include directories searched
for headers?

Sorry, but this is frustrating the hell out of me. Try to install packages
in non-standard locations, and all of a sudden, 1 million bugs fly out of the
woodwork. Any hints on how to get around this are much appreciated.

Ed