what is stdinc and how can I get where it is ?

[loody]

Dear all:
in gcc document there is an option as
-nostdinc
Do not search the standard system directories for header
files.  Only the directories you have specified with -I
options  (and the directory of the current file, if appropriate)
are searched
Is that used to tell where the headers that gcc can get the size of
some already define data types?

If my assumption is correct, is there any command or options I can use
to check where is the path that my gcc search for, since I always get
error messages as "cannot find stddef.h" ?

I have type "gcc -v" but i have no idea which one can tell me where
the stdinc path it looks for?
appreciate your help,
miloody