[cfe-dev] Question about Casting Away Constness

Bill Wendling isanbard at gmail.com
Thu Aug 2 23:43:30 PDT 2007

Hi all,

I have a question about implementation of performing a casting away  
constness check. Here's an example representing the wording in the  
standard. If Tn and Xn represent types, then for two pointer types:

    X1 is T1 cv1,1 * cv1,2 * cv1,3 * cv1,N=4 *
    X2 is T2 cv2,1 * cv2,2 * cv2,3 * cv2,4 * cv2,5 * cv2,6 * cv2,M=7 *

    K = min(N,M);

casting from X1 to X2 casts away constness if for a non-pointer type  
T there does not exist an implicit conversion (clause 4) from:

(1)   T cv1,1 * cv1,2 * cv1,3 * cv1,4 *


(2)   T cv2,4 * cv2,5 * cv2,6 * cv2,7 *

How would you suggest going about this? I was thinking of looping  
through the pointees of the pointers to try to come up with (1) and  
(2) in this example. Is this feasible? After we get that, is there a  
way to "fake" a type (the 'T' in this example) so that we can do the  
implicit conversion check? And, lastly, is there already a check for  
implicit conversions?

Sorry that this is kind of a lot, and that some of it is basic. I  
just don't want to waste a lot of time. :-)


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