serge-sans-paille added inline comments.
================
Comment at: clang/test/Sema/unbounded-array-bounds.c:101
+ char tail[1]; // addr16-note {{declared here}} addr32-note {{declared here}}
+} fam1;
+
----------------
msebor wrote:
> msebor wrote:
> > There's a difference between the sizes of `fam1` and `fam` that makes
> > accesses to the four leading elements of `fam1.tail` strictly in bounds,
> > while no access to either `fam.tail` or `fam0.tail` is (`sizeof fam` is the
> > same as `sizeof int` while `sizeof fam1` is equal to `sizeof (int[2])` on
> > common targets). It would be helpful to capture that difference in the
> > tests, both for the warning and for `__builtin_object_size`.
> >
> > There should also be a difference between accessing elements of an object
> > of an initialized struct with a flexible array member (i.e., one whose size
> > is known) and those of an object that's only declared but that's defined in
> > some other translation unit. Since the size of the object is determined by
> > its initializer, it should be reflected in `__builtin_object_size` and
> > accesses to it checked by `-Warray-bounds`. The size of the latter object
> > is unknown it must be assumed to be `PTRDIFF_MAX - sizeof (int) - 1`. It
> > would also be helpful to add tests for these cases.
> >
> > As far as I can see, none of these cases seems to be handled quite right on
> > trunk. For example, the size of `s` below should be 8 but Clang evaluates
> > `__builtin_object_size(&s, N)` to 4, without diagnosing any past-the-end
> > accesses to `s.a`:
> > ```
> > struct S {
> > int n;
> > char a[];
> > } s = { 1, { 2, 3, 4, 5 } };
> > ```
> I opened [[ https://github.com/llvm/llvm-project/issues/57860 | PR #57860 ]]
> to better show what I mean.
Agreed. I suggest we discuss that in this PR, while me merge this "code cleanup
with enhancement", if @aaron.ballman agrees :-)
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D133108/new/
https://reviews.llvm.org/D133108
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