stack questions

[Dave Klint]

Just a few basic questions about stack management and what
is gcc dependant and what is platform dependant:

Some facts that I hope I'm not wrong on:
1) each argument to a function is pushed on to the stack so that
   the last argument in the list is highest on the stack.
2) the return value of a function is contained in %eax (on x86).
3) the return address of a function is (should be) contained at the 
   top of the stack when "ret" is called
4) after a function call, gcc adds 4*number_of_parameters to the
   stack pointer.  A function with 3 arguments would have 12 added
   to the stack pointer after the function call.

Because of this, I assume that external functions (implemented in
asm, for example) would get to its parameters by using offsets
from the stack pointer, and should never have unbalanced push/pop's.

Is there any other strangeness in the parameter passing in gcc 
that I should be aware of?  

Thanks in advance,
-dave