On Fri, Feb 19, 2016 at 6:50 PM, Conrad Meyer <c...@freebsd.org> wrote:
> On Fri, Feb 19, 2016 at 3:14 PM, Benjamin Kaduk <bjkf...@gmail.com> wrote: > > On Fri, Feb 19, 2016 at 5:06 PM, Gleb Smirnoff <gleb...@freebsd.org> > wrote: > >> Isn't zero filling part of the standard? I don't see why lack of > >> explicit zeroing is a warning? Looks a false warning to me. > > > > > > It is not quite as simple as this would make it sound. The elements or > > members of an aggregate (e.g.) structure type are initialized as if it > were > > an object of static storage duration (i.e., to zero) if the initializer > list > > does not contain enough initializers for all members of the aggregate > type, > > per item 21 of section 6.7.8 of n1256.pdf. However, such initialization > > does not necessarily need to zero any padding bytes that are present, > which > > may take unspecified values. Personally, I think this particular clang > > warning can be too aggressive, especially for complex structs, but on the > > other hand given the indeterminateness of padding, bzero/memset are > often a > > better choice anyway. > > > By definition, padding byte contents are unused. There is no reason > their values matter one way or another, so why do we care about the > distinction between bzero and member zero initialization? > Well, you can access them by treating the object as an array of char, and then memory sanitizer will complain about the uninitialized access, as in https://github.com/openssl/openssl/commit/f0496ad71fbacccf5a95f40d31d251bc8cf9dcfb -Ben P.S. Not really apropos of anything, but clang also has -Weverything which is just what it sounds like (as opposed to -Wall), which is a great way to expose several other warnings that Bruce will call bugs :) _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
