On Nov 8, 2005, at 18:23:27, linas wrote:
Off-topic: There's actually a neat little trick in C++ that can
help avoid accidentally passing null pointers. One can declare
function declarations as:
int func (sturct blah &v) {
v.a ++;
return v.b;
}
The ampersand says "pass argument by reference (so as to get arg
passing efficiency) but force coder to write code as if they were
passing by value" As a result, it gets difficult to pass null
pointers (for reasons similar to the difficulty of passing null
pointers in Java (and yes, I loathe Java, sorry to subject you to
that)) Anyway, that's a C++ trick only; I wish it was in C so I
could experiment more and find out if I like it or hate it.
That technique tends to cause more problems than it solves. If I
write the following code:
struct foo the_leftmost_foo = get_leftmost_foo();
do_some_stuff(the_leftmost_foo);
How do I know what it is going to do? Will it modify
the_leftmost_foo, or is it a pass-by-value as it appears? This is
just as bad as defining a macro some_macro(foo,bar) that does (foo =
bar), it's _really_ hard to tell what it does, especially when you
aren't all that familiar with the code. A much better solution is this:
void do_some_stuff(struct foo *the_foo) __attribute__((__nonnull__(1)));
do_some_stuff(&the_leftmost_foo);
That ensures that the first argument cannot be explicitly passed as
null, while still being quite obvious to the programmer what it's doing.
Cheers,
Kyle Moffett
--
They _will_ find opposing experts to say it isn't, if you push hard
enough the wrong way. Idiots with a PhD aren't hard to buy.
-- Rob Landley
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