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Writing lots of ZST's is unsound #79

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finnbear opened this issue Jan 1, 2025 · 0 comments · May be fixed by #80

finnbear commented Jan 1, 2025

Hello, I noticed a case in which speedy invokes undefined behavior:

use speedy::Writable;
fn main() {
    let chonk = vec![(); 0x7FFFFFFF_FFFFFFFF + 1];
    let _ = chonk.write_to_vec();
}

error: Undefined Behavior: entering unreachable code
   --> /home/finnb/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/speedy-0.8.7/src/writable_impl.rs:245:9
    |
245 |         unsafe_is_length!( self.len() );
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ entering unreachable code

I recommend skipping the assertion if std::mem::size_of::<T>() == 0.

The text was updated successfully, but these errors were encountered:

finnbear linked a pull request

that will close this issue

Fix #79 - avoid UB when writing lots of ZST's #80

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