Re: reporting typedef errors automatically

[Peter Nilsson]

Harald van D©¦k <true...@gmail. comwrote:

...
When you define an array of length 0 the compiler
will let you know you're doing something wrong.

It is a constraint violation. Unfortunately, it's also
not an uncommon extension to allow zero sized arrays,
particularly at the end of a struct. So, I prefer
((need) ? 1 : -1) for compile time asserts.

--
Peter

[Harald van =?UTF-8?b?RMSzaw==?=]

Re: reporting typedef errors automatically

On Thu, 29 May 2008 14:57:57 -0700, Peter Nilsson wrote:

Harald van Dijk <true...@gmail. comwrote:

>...
>When you define an array of length 0 the compiler will let you know
>you're doing something wrong.

>
It is a constraint violation. Unfortunately, it's also not an uncommon
extension to allow zero sized arrays, particularly at the end of a
struct. So, I prefer ((need) ? 1 : -1) for compile time asserts.

I agree, that's a better idea. However, I seem to recall reading that
implementations exist that accept negative array length constants as well,
and that it's even safer to use bit-field widths because of that.

struct check {
int member : (... ? 1 : -1);
};

As far as standard C is concerned, all are equivalent, as all violate a
constraint if the check fails, but in practise, it's good to do whatever's
reasonably possible to ensure the diagnostic is a fatal one.