On 9/14/2010 3:56 AM, Seth Hetu wrote:
I'd definitely avoid this situation with gusto. Consider passing '3'
(just the number) as "by ref" into the parameter 'x' ---what happens
if the compiler inlines that variable, copying it to each place the
variable is used inside the function? That becomes problematic for,
e.g.,:
x = 10
....which becomes:
3 = 10
That's not how function inlining works. And fbc is miles off doing any
optimisations as significant as function inlining anyway.
I was under the impression that function inlining (e.g., inline
expansion) included constant propagation as one of its steps.
That, at least, is the reason it's illegal in C++ ---not sure what
the FB compiler says if you try this.
I don't think so. C++ can pass other types of temporary values by
reference, so I assume the reason it's illegal is that if you're
passing "3" by reference, it's probably an unintentional bug. Passing
by reference indicates that you want to pass a *variable* instead of a
value.
And like I said, it works in FB.
What you said makes more sense in this case. But then if passing by
reference always works in FB, what happens if you pass '3' as a
parameter by reference? Does it push a temporary variable to the stack
and store '3' in there? Does it declare a temporary variable on the
heap and pass its memory address to the function?
Why is there so much confusion by this? Variable allocation is trivial
to do at compile time. If FB needs a temporary variable to pass to a
BYREF argument, it just adds sizeof(thatvariable) to the stack size and
calls it a night.
Or, looking at it from a different angle, why are you NOT surprised that
you can do this in C?
myfunction("Literal string: omg no variable!");
I'm just curious how FB manages this without corrupting memory. It
seems like such a weird design choice.
Consider this. In QB, everything was BYREF by default. So, this had to
be legal:
sub mysub(myparam as integer)
REM whatever
end sub
mysub 1
If it weren't legal, you'd get an error on a seemingly standard BASIC
program.
-->Seth
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