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RE: [PATCH] Add new cpp predef macro __SAFE_FILE__ to improve compile-time assertions.
On 24 April 2007 18:22, Richard Henderson wrote:
> On Sun, Apr 22, 2007 at 01:58:08PM +0100, Dave Korn wrote:
>> A quick survey of the standard techniques for compile-time assertions[*]
>> reveals they all have to work around one underlying limitation of the
>> preprocessor: there's no way to automatically generate a (project-wide)
>> unique identifier using a preprocessor macro.
>
> Why do you need one?
>
> #define COMPILE_TIME_ASSERT(e) \
> extern int compile_time_assert[(e) ? 1 : -1]
>
> External declarations can appear over and over again, provided
> that they are identical, and in this case the only time they
> aren't is when the assertion fails.
>
> The unused external declaration merely gets discarded.
Yes, you're correct (and only the second person to point this out), for some
reason (faulty memory?) I was expecting a common symbol to be emitted.
Still, is there never another situation which might call for the ability to
generate a unique symbol using preprocessor macros? Currently, it is
completely impossible.
cheers,
DaveK
--
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