[cfe-dev] Helpers to compute sizeof/alignof/offsetof?

[Ted Kremenek]

On Jan 17, 2008, at 7:35 PM, Chris Lattner wrote:

>>
>> For the "generic" method that returns the sizeof, we may consider
>> having it return a variant type that wraps an integer primitive.  The
>> variant could also have a flag indicating whether or the not the
>> sizeof returned is valid.  This way we can have the generic method
>> return "unknown" for VLAs if clients just blindly call sizeof on VLA
>> types.  For example:
>
> How about a really simple variant: int64_t :)
>
> Define -1 to be "invalid" and -2 to be "vla" and you're golden.
>
> -Chris

That's a nice solution because of its simplicity.  One thing that I  
like about the solution that I proposed is the extra checking done by  
the type system, the automatic assertions, and a clear API to query  
the sizeof value instead of checking for magic numbers (just use  
methods:  isVLA(), isValid(), etc.).  Using a thin class also doesn't  
cost us anything in terms of runtime overhead, although it will have a  
negligible impact on compile time.