It's exactly this way,
&record is the address of the structure named record,
and the address is passed "by value", that is,
copied to the stack.
When teaching C language, I always say, that all arguments are passed
"by value",
even x (if x is a vector) is passed "by value" because x is the same as
&x[0],
which is the address of the first element of x.
there are more such equivalences:
*x is the same as x[0]
*(x+1) is the same as x[1]
and even if you have a pointer p instead of a vector x, for example
p = &x[5];
or
p = x + 5;
(which is the same)
you can then use the expressions
*p
p[0]
*(p+1)
p[1]
which refer to the element x[5] and x[6], respectively.
This is completely independent of the base type of x and p,
it could be char, int, long, double or a structure type.
By the way: the term "by value" is inherited from ALGOL; there are
two parameter passing mechanisms in ALGOL - by value and by name -
no by reference. By name is similar to by reference, but more complicated -
and not the same.
I would say that "by value" tries to give a "logical" description of the
parameter passing mechanism, where "copy to the stack" is a
technical implementation of the parameter passing mechanism -
there could be other ones. Same goes for "by reference" and
"by name".
It is interesting to compare the languages on their parameter passing
mechanisms:
ALGOL: by value - by name
FORTRAN: by reference
PL/1: by reference - dummy arguments by reference (with paranthese) -
only recently by value
PASCAL: by value - by reference
C: always by value - by reference only by explicitly passing pointers
Kind regards
Bernd
Am 01.07.2013 01:15, schrieb Steve Comstock:
On 6/30/2013 3:58 PM, Bernd Oppolzer wrote:
As I pointed out earlier, C NEVER passes arguments by reference.
Well, if you pass, say &record then the address of record
is passed in the argument list, so record is passed by
reference. However, one could argue that '&record' is a
pointer and the pointer is being passed by value so that
the data is being passed by reference.
Angels and pin heads, eh?
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