[webkit-dev] Using C++ constant pointers (type_name * const) in WebKit
In a discussion on Bug 71921, Antti, Darin Adler and I started a discussion about using C++ constant pointers in WebKit. Does the WebKit community have a consensus opinion on the matter? * Pros - Documents use of variable. - Prevents misuse of variable in a later patch (by a different author) through enforcement of pointer const-ness. - May help compiler optimize code. (We weren't sure whether modern compilers do this on their own or not.) * Cons - Darin Adler doesn't ever recall fixing a bug in WebKit where a constant pointer would have helped. - Slightly more verbose syntax for constant pointers to a constant string (const char * const pointer;) or even a constant pointer to a mutable string (char * const pointer;). Dave ___ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
Re: [webkit-dev] Using C++ constant pointers (type_name * const) in WebKit
On Mon, Nov 28, 2011 at 1:38 PM, David Kilzer ddkil...@webkit.org wrote: In a discussion on Bug 71921https://bugs.webkit.org/show_bug.cgi?id=71921, Antti, Darin Adler and I started a discussion about using C++ constant pointers in WebKit. Does the WebKit community have a consensus opinion on the matter? It seems like the const in T * const idName is equally useful (or useless) to the const in const T idName. Both are saying that |idName| (as opposed to what it points to, in the first case) is constant. In both cases people are rarely in that habit of using const, especially when |idName| is a local. The same pros and cons seem to apply to both. Therefore I would suggest that if we want to make a rule, we make it apply to both cases. I personally like using const as much as possible (without overstepping logical constness limits), but I also suspect my view is the minority. PK ___ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
Re: [webkit-dev] Using C++ constant pointers (type_name * const) in WebKit
On Mon, Nov 28, 2011 at 1:38 PM, David Kilzer ddkil...@webkit.org wrote: In a discussion on Bug 71921https://bugs.webkit.org/show_bug.cgi?id=71921, Antti, Darin Adler and I started a discussion about using C++ constant pointers in WebKit. Does the WebKit community have a consensus opinion on the matter? * Pros - Documents use of variable. - Prevents misuse of variable in a later patch (by a different author) through enforcement of pointer const-ness. - May help compiler optimize code. (We weren't sure whether modern compilers do this on their own or not.) Don't think so. As far as I know, C++ compilers ignore const for the purpose of code optimization because we can always re-cast it to non-const variable. On the other hand, modern optimizing compilers might do SSA-based constanthttp://en.wikipedia.org/wiki/Sparse_conditional_constant_propagation propagation http://gcc.gnu.org/news/ssa-ccp.html regardless of constness of a variable. * Cons - Darin Adler doesn't ever recall fixing a bug in WebKit where a constant pointer would have helped. - Slightly more verbose syntax for constant pointers to a constant string (const char * const pointer;) or even a constant pointer to a mutable string (char * const pointer;). I'd argue against using constant pointers simply because I don't think the existing WebKit code uses it, and I don't see much benefit in comparison to pointers or references to const objects. - Ryosuke ___ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
