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a slice fill is now turned into a memset even when using miri #417

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Merged
merged 1 commit into from
Oct 16, 2025
Merged

a slice fill is now turned into a memset even when using miri #417

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11 changes: 1 addition & 10 deletions zlib-rs/src/deflate.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -804,16 +804,7 @@ fn lm_init(state: &mut State) {
state.window_size = 2 * state.w_size;

// zlib uses CLEAR_HASH here
crate::cfg_select!(
miri => {
// Miri does not turn `.fill(0)` into a memset
// See https://github.com/rust-lang/rust/issues/147271.
unsafe { core::ptr::write_bytes(state.head.as_mut_ptr(), 0u8, 1) };
}
_ => {
state.head.as_mut_slice().fill(0);
}
);
state.head.as_mut_slice().fill(0);

// Set the default configuration parameters:
lm_set_level(state, state.level);
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11 changes: 1 addition & 10 deletions zlib-rs/src/deflate/sym_buf.rs
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Expand Up @@ -36,16 +36,7 @@ impl<'a> SymBuf<'a> {
/// The number of initialized bytes is not changed, and the contents of the buffer are not modified.
#[inline]
pub fn clear(&mut self) {
crate::cfg_select!(
miri => {
// Miri does not turn `.fill(0)` into a memset
// See https://github.com/rust-lang/rust/issues/147271.
unsafe { core::ptr::write_bytes(self.buf.as_mut_ptr(), 0u8, self.buf.len()) };
}
_ => {
self.buf.as_mut_slice().fill(0);
}
);
self.buf.as_mut_slice().fill(0);
self.filled = 0;
}

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21 changes: 0 additions & 21 deletions zlib-rs/src/lib.rs
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Expand Up @@ -26,27 +26,6 @@ macro_rules! trace {
};
}

#[macro_export]
macro_rules! cfg_select {
({ $($tt:tt)* }) => {{
$crate::cfg_select! { $($tt)* }
}};
(_ => { $($output:tt)* }) => {
$($output)*
};
(
$cfg:meta => $output:tt
$($( $rest:tt )+)?
) => {
#[cfg($cfg)]
$crate::cfg_select! { _ => $output }
$(
#[cfg(not($cfg))]
$crate::cfg_select! { $($rest)+ }
)?
}
}

/// Maximum size of the dynamic table. The maximum number of code structures is
/// 1924, which is the sum of 1332 for literal/length codes and 592 for distance
/// codes. These values were found by exhaustive searches using the program
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