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Safe pointer-to-member functionality for rust

License: Apache License 2.0

Rust 100.00%

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kim366 ralfjung pranjalssh mexus ogoffart rsschermer ycysdf virxec jules-bertholet joshlf lann

rust-field-offset's Issues

causes UB by calling mem::zeroed on any type

This code is highly problematic:

    pub unsafe fn new<F: for<'a> FnOnce(&'a T) -> &'a U>(f: F) -> Self {
        // Construct a "fake" T. It's not valid, but the lambda shouldn't
        // actually access it (which is why this is unsafe)
        let x = mem::zeroed();

If T is, for example, a struct containing reference type, then this causes UB by initializing a reference with 0. The comment seems to say that it is okay to do this as long as x is not accessed; that is not correct.

That said, there currently is no correct way to do what you want. This bug can only really be fixed once MaybeUninit gets stabilized.

(I also feel really uneasy with the extend to which this relies on type inference, but YMMV.^^)

Access fields of an enum variant

I cannot seem to figure out how to get the offset of fields in a enum variant. I tried Enum::Variant => field but that seems to be interfering with the second macro.

Compilation error with version 0.3.2

I'm getting following error using rust nightly:

error[E0658]: `if` is not allowed in a `const fn`
   --> /home/pranjalssh/.cargo/registry/src/github.com-1ecc6299db9ec823/field-offset-0.3.2/src/lib.rs:126:9
    |
126 |         assert!(offset + mem::size_of::<U>() <= mem::size_of::<T>());
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #49146 <https://github.com/rust-lang/rust/issues/49146> for more information
    = help: add `#![feature(const_if_match)]` to the crate attributes to enable
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to previous error

For more information about this error, try `rustc --explain E0658`.
error: could not compile `field-offset`.

feature const_fn has been removed

I'm getting this in rust-nightly CI

   Compiling field-offset v0.3.3
error[E0557]: feature has been removed
 --> /github/home/.cargo/registry/src/github.com-1ecc6299db9ec823/field-offset-0.3.3/src/lib.rs:3:53
  |
3 | #![cfg_attr(fieldoffset_assert_in_const_fn, feature(const_fn))]
  |                                                     ^^^^^^^^ feature has been removed
  |
  = note: split into finer-grained feature gates

Warning from offset_of macro if called from an unsafe block

I would expect this to work without the warning.

#[macro_use]
extern crate field_offset;

struct Foo {
    bar: u8
}

pub unsafe fn f() {
    offset_of!(Foo => bar);
}

warning: unnecessary `unsafe` block
 --> src/main.rs:9:5
  |
8 | pub unsafe fn f() {
  | ----------------- because it's nested under this `unsafe` fn
9 |     offset_of!(Foo => bar);
  |     ^^^^^^^^^^^^^^^^^^^^^^^ unnecessary `unsafe` block
  |
  = note: #[warn(unused_unsafe)] on by default

offset_of! overflows stack when called on BIG structs

I'm trying to initialize a struct on the heap, but field-offset just overflows the stack whenever I try to get the field offset xD

diggsey / rust-field-offset Goto Github PK

rust-field-offset's People

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rust-field-offset's Issues

causes UB by calling mem::zeroed on any type

Access fields of an enum variant

Compilation error with version 0.3.2

feature const_fn has been removed

Warning from offset_of macro if called from an unsafe block

offset_of! overflows stack when called on BIG structs

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