https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108871
--- Comment #7 from Jonny Grant <jg at jguk dot org> --- (In reply to Jakub Jelinek from comment #6) > (In reply to Jonathan Wakely from comment #5) > > (In reply to Andrew Pinski from comment #3) > > > *** Bug 108893 has been marked as a duplicate of this bug. *** > > > > N.B. this one is about __attribute__((access(read_only, 1))) not nonnull. > > The docs already seem to imply that it requires a non-null pointer: > > > > The read_only access mode specifies that the pointer to which it applies > > is used to > > read the referenced object but not write to it. Unless the argument > > specifying the > > size of the access denoted by size-index is zero, the referenced object > > must be > > initialized. > > > > If a non-zero size implies an initialized object, then it also implies a > > non-null pointer (since a null pointer doesn't point to an initialized > > object). > > > > I don't know if we want this PR to be specific to the nonnull attribute, or > > if it makes sense to use it for access(read_only) too. > > On the other side, looking at glibc sources, access attributes there are > used on many functions together with nonnull attributes for the same > arguments and in many cases in places where there are not nonnull > attributes. So, making access attribute imply non-null might not be > desirable in real-world unless it is already implied. > So it might be just that it is badly documented. Hi Jakub, Did you manage to get gcc to give a build warning from those __attr_access read_only lines in glibc? I haven't found a way to activate any build warnings. attribute nonnull seems to be used by optimizer to remove any NULL checks it finds.
