Re: C function return value?
From: Chris Torek (nospam_at_torek.net)
Date: 12/29/03
- Next message: CBFalconer: "Re: structs passed by value"
- Previous message: Alexander Bartolich: "Re: Reverse search in a singly-linked list"
- In reply to: Ravindranath Gummadidala: "C function return value?"
- Next in thread: Richard Heathfield: "Re: C function return value?"
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
Date: 29 Dec 2003 03:22:12 GMT
In article <news:Pine.SOL.4.56.0312282139360.19311@hadar.cse.Buffalo.EDU>
Ravindranath Gummadidala <rg27@cse.buffalo.edu> writes:
>I am trying to understand the C function call mechanism. Please bear with
>me as I state what I know:
>
>"every invocation of a function causes a frame for that function to be
>pushed on stack. this contains the arguments this function was called
>with, address to return to after return from this function (the location
>in the previous stack frame), location of previous frame on stack (base or
>start of this frame) and local variables of this function"
This is *a* method. It is not *the* method. Different C compilers
use different methods. (In particular, one common technique in
use today is not to have the parameters and return-address on any
stack at all, nor to have separate stack and frame pointers. If
the return address is in a register -- as done by the hardware on
MIPS and SPARC and PowerPC, for instance -- then leaf functions,
i.e., functions that do not call other functions, can just leave
it there and "return" using a jump-register instruction. If all
its local variables fit in any registers left over after accounting
for parameter registers, a leaf function often needs no memory at
all!)
>my question is how is a value returned from this function.
In a machine- and/or compiler-specific manner.
Three common techniques are to put the return values into registers,
or to return pointers to the return values (again often in registers),
or to have the caller pass, as "hidden" extra arguments, pointers
to the places the return values should go.
If you want to learn the method for a particular machine and/or
compiler, consult the appropriate documentation (if any) or newsgroup
(if any), or read the compiled code or the compiler code. Note
that information gleaned via the latter two methods (reverse
engineering) is often "subject to change without notice".
-- In-Real-Life: Chris Torek, Wind River Systems Salt Lake City, UT, USA (40°39.22'N, 111°50.29'W) +1 801 277 2603 email: forget about it http://web.torek.net/torek/index.html Reading email is like searching for food in the garbage, thanks to spammers.
- Next message: CBFalconer: "Re: structs passed by value"
- Previous message: Alexander Bartolich: "Re: Reverse search in a singly-linked list"
- In reply to: Ravindranath Gummadidala: "C function return value?"
- Next in thread: Richard Heathfield: "Re: C function return value?"
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
Relevant Pages
|
