On Thursday 17 January 2008 11:51:49 pm Giacomo Catenazzi wrote: > Linus Torvalds wrote: > > No, I'm saying that "const" has absolutely *zero* meaning on writes to an > > object through _other_ pointers (or direct access) to the object. > > Hints: "restrict" is the C99 keyword for such requirement (or better > "const restrict")
The restrict keyword controls aliasing, to be exact. And I'm skeptical that inserting const there would do anything at all. > BTW I think C use non const free as a BIG warning about not to be > to "smart" on optimization. I must ask what relationship you think the const keyword has to compiler optimizations. I know of none, and I've yet to see that keyword cause any difference in the resulting assembly. It forces you to make your code clean and well-structured, but that's about it. Of course, it would be an interesting experiment to potentially redefine the const keyword to have stronger semantics, such as having the compiler assume that a function taking a const pointer argument will not modify the memory the pointer points to, and thus saving itself a memory load in the caller after the function executes, as long as the data is not global. I imagine that this would lead to some simple and measurable optimizations, all the while (this is where I get into hand-waving territory) breaking a minimum amount of code in current existence. But that is emphatically not how C is currently defined, and you're basically inventing an entirely new language... C2009 perhaps? :-) -- Vadim Lobanov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
