yilin0518 commented on issue #9286:
URL: https://github.com/apache/arrow-rs/issues/9286#issuecomment-3819021971
> Yes this looks like a bug; I'll push a PR fix, thanks for identifying this
Related to this bug, I found that using the `struct IntervalMonthDayNano` as
the type of BufferBuilder, will produce another scenario. Look the following
code snippet:
```rust
#![feature(allocator_api)]
use arrow_buffer::*;
fn main() {
let mut v10 = <builder::BufferBuilder::<IntervalMonthDayNano> as
std::default::Default>::default();
let v11: &'_ mut builder::BufferBuilder::<IntervalMonthDayNano> = &mut
v10;
let v12 = IntervalMonthDayNano { months: 98, days: 78, nanoseconds: 117
};
builder::BufferBuilder::<IntervalMonthDayNano>::append(v11, v12);
let v13: &'_ builder::BufferBuilder::<IntervalMonthDayNano> = &v10;
let v14 = builder::BufferBuilder::<IntervalMonthDayNano>::capacity(v13);
let v15: &'_ mut builder::BufferBuilder::<IntervalMonthDayNano> = &mut
v10;
builder::BufferBuilder::<IntervalMonthDayNano>::truncate(v15, v14);
let v25: &'_ builder::BufferBuilder::<IntervalMonthDayNano> = &v10;
let v26 = builder::BufferBuilder::<IntervalMonthDayNano>::as_slice(v25);
println!("v26: {:?}",v26);
}
```
Despite `as_slice` or `as_slice_mut`, miri report the same error message:
```bash
error: Undefined Behavior: reading memory at alloc230[0x10..0x14], but
memory is uninitialized at [0x10..0x14], and this operation requires
initialized memory
-->
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/num.rs:599:5
|
599 | impl_Display!(i8, u8, i16, u16, i32, u32, i64, u64, isize, usize;
as u64 into display_u64);
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Undefined Behavior occurred here
|
= help: this indicates a bug in the program: it performed an invalid
operation, and caused Undefined Behavior
= help: see
https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html
for further information
= note: BACKTRACE:
= note: inside `core::fmt::num::imp::<impl std::fmt::Display for
i32>::fmt` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/num.rs:164:45:
164:50
= note: inside `core::fmt::num::<impl std::fmt::Debug for i32>::fmt` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/num.rs:91:25:
91:51
= note: inside closure at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/builders.rs:133:35:
133:47
= note: inside closure at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/builders.rs:162:17:
162:36
= note: inside `std::result::Result::<(),
std::fmt::Error>::and_then::<(), {closure@std::fmt::DebugStruct<'_,
'_>::field_with<{closure@std::fmt::DebugStruct<'_,
'_>::field::{closure#0}}>::{closure#0}}>` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/result.rs:1493:22:
1493:27
= note: inside `std::fmt::DebugStruct::<'_,
'_>::field_with::<{closure@std::fmt::DebugStruct<'_, '_>::field::{closure#0}}>`
at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/builders.rs:145:23:
164:11
= note: inside `std::fmt::DebugStruct::<'_, '_>::field` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/builders.rs:133:9:
133:48
= note: inside `std::fmt::Formatter::<'_>::debug_struct_field3_finish`
at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/mod.rs:2496:9:
2496:37
= note: inside `<arrow_buffer::IntervalMonthDayNano as
std::fmt::Debug>::fmt` at
/home/chenyl/projects/check_UB/arrow-buffer-57.2.0/src/interval.rs:68:10: 68:15
= note: inside `<&arrow_buffer::IntervalMonthDayNano as
std::fmt::Debug>::fmt` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/mod.rs:2865:62:
2865:82
= note: inside closure at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/builders.rs:741:35:
741:47
= note: inside closure at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/builders.rs:474:17:
474:36
= note: inside `std::result::Result::<(),
std::fmt::Error>::and_then::<(), {closure@core::fmt::builders::DebugInner<'_,
'_>::entry_with<{closure@std::fmt::DebugList<'_,
'_>::entry::{closure#0}}>::{closure#0}}>` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/result.rs:1493:22:
1493:27
= note: inside `core::fmt::builders::DebugInner::<'_,
'_>::entry_with::<{closure@std::fmt::DebugList<'_, '_>::entry::{closure#0}}>`
at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/builders.rs:460:23:
476:11
= note: inside `std::fmt::DebugList::<'_, '_>::entry` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/builders.rs:741:9:
741:48
= note: inside `std::fmt::DebugList::<'_,
'_>::entries::<&arrow_buffer::IntervalMonthDayNano, std::slice::Iter<'_,
arrow_buffer::IntervalMonthDayNano>>` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/builders.rs:788:13:
788:31
= note: inside `<[arrow_buffer::IntervalMonthDayNano] as
std::fmt::Debug>::fmt` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/mod.rs:3116:9:
3116:44
= note: inside `<&[arrow_buffer::IntervalMonthDayNano] as
std::fmt::Debug>::fmt` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/mod.rs:2865:62:
2865:82
= note: inside `core::fmt::rt::Argument::<'_>::fmt` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/rt.rs:152:76:
152:95
= note: inside `std::fmt::write` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/mod.rs:1684:17:
1686:80
= note: inside `std::io::default_write_fmt::<std::io::StdoutLock<'_>>`
at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/mod.rs:614:11:
614:40
= note: inside `<std::io::StdoutLock<'_> as std::io::Write>::write_fmt`
at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/mod.rs:1969:13:
1969:42
= note: inside `<&std::io::Stdout as std::io::Write>::write_fmt` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/stdio.rs:834:9:
834:36
= note: inside `<std::io::Stdout as std::io::Write>::write_fmt` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/stdio.rs:808:9:
808:33
= note: inside `std::io::stdio::print_to::<std::io::Stdout>` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/stdio.rs:1164:21:
1164:47
= note: inside `std::io::_print` at
/home/chenyl/.rustup/toolchains/nightly-2025-12-06-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/stdio.rs:1275:5:
1275:37
note: inside `main`
--> src/main.rs:14:5
|
14 | println!("v26: {:?}",v26);
| ^^^^^^^^^^^^^^^^^^^^^^^^^
= note: this error originates in the macro `impl_Display` which comes
from the expansion of the macro `println` (in Nightly builds, run with -Z
macro-backtrace for more info)
Uninitialized memory occurred at alloc230[0x10..0x14], in this allocation:
alloc230 (Rust heap, size: 64, align: 128) {
0x00 │ 62 00 00 00 4e 00 00 00 75 00 00 00 00 00 00 00 │ b...N...u.......
0x10 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
0x20 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
0x30 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
}
note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full`
for a verbose backtrace
error: aborting due to 1 previous error
```
Different with **pointer not dereferenceable**, I try to make this code
shorter, but remove several lines of this snippet will not output this UB.
Maybe it contains another potential error. Hoping you can take a view!
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