void added inline comments.
================
Comment at: clang/test/SemaCXX/array-bounds.cpp:240
- ((char*)foo)[sizeof(foo)] = '\0'; // expected-warning {{array index 32768
is past the end of the array (which contains 32768 elements)}}
+ ((char*)foo)[sizeof(foo)] = '\0'; // expected-warning {{array index 32768
is past the end of the array (which contains 4096 elements)}}
----------------
aaron.ballman wrote:
> void wrote:
> > serge-sans-paille wrote:
> > > kees wrote:
> > > > serge-sans-paille wrote:
> > > > > I find this new message quite confusing, because the array index is
> > > > > given in terms of char elements, while the array size is given in
> > > > > terms of double elements. I actually find the original message more
> > > > > consistent to that respect.
> > > > Perhaps show both element count and byte offset?
> > > >
> > > > `array index $count is $(bytes - end_of_array_in_bytes) past the end of
> > > > the array (which contains $end_of_array_in_bytes bytes of
> > > > $array_max_index elements)`
> > > if we have no cast, I find the version without the patch just fine.
> > >
> > > If we have a cast, I suggest we just express the result in bytes,
> > > something along those lines (inspired by your suggestion):
> > >
> > > array index $count is $(bytes - end_of_array_in_bytes) bytes past the
> > > end of the allocated memory for that array (which contains
> > > $end_of_array_in_bytes bytes)
> > I so far have this. It looks not too bad even for the non-cast. Thoughts?
> >
> > ```
> > $ cat ab.c
> > void test_pr10771() {
> > double foo[4096]; // expected-note {{array 'foo' declared here}}
> >
> > ((char*)foo)[sizeof(foo)] = '\0'; // expected-warning {{array index
> > 32768 is past the end of the array (which contains 4096 elements of type
> > 'double[4096])}}
> > foo[4098] = '\0'; // expected-warning {{array index 32768 is past the
> > end of the array (which contains 4096 elements of type 'double[4096])}}
> > }
> > $ clang++ -x c++ -o /dev/null -S -std=c++14 ~/llvm/ab.c
> > /home/morbo/llvm/ab.c:4:13: warning: array index 32768 is 0 bytes past the
> > end of the array (that has type 'double[4096]') [-Warray-bounds]
> > ((char*)foo)[sizeof(foo)] = '\0'; // expected-warning {{array index
> > 32768 is past the end of the array (which contains 4096 elements of type
> > 'double[4096])}}
> > ^ ~~~~~~~~~~~
> > /home/morbo/llvm/ab.c:2:5: note: array 'foo' declared here
> > double foo[4096]; // expected-note {{array 'foo' declared here}}
> > ^
> > /home/morbo/llvm/ab.c:5:5: warning: array index 4098 is 16 bytes past the
> > end of the array (that has type 'double[4096]') [-Warray-bounds]
> > foo[4098] = '\0'; // expected-warning {{array index 32768 is past the
> > end of the array (which contains 4096 elements of type 'double[4096])}}
> > ^ ~~~~
> > /home/morbo/llvm/ab.c:2:5: note: array 'foo' declared here
> > double foo[4096]; // expected-note {{array 'foo' declared here}}
> > ^
> > 2 warnings generated.
> > ```
> The part I struggle with is the "is 0 bytes past the end of the array" --
> that reads as if it's not past the end of the array at all because it's
> saying "You've accessed right up to the end of the array; congratulations on
> your very careful use!".
Okay. How about this then?
```
Typical diagnostic:
warning: array index %{index} is past the end of the array (that has type
%{type})
Diagnostic if the array is cast to something else:
warning: array index %{index} is past the end of the array (that has type
%{type}, cast to ${cast_type})
```
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D135920/new/
https://reviews.llvm.org/D135920
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