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std: maintain CStringArray null-termination even if Vec::push panics #155774

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std: maintain CStringArray null-termination even if Vec::push panics #155774

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8 changes: 5 additions & 3 deletions library/std/src/sys/process/unix/common/cstring_array.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -35,10 +35,12 @@ impl CStringArray {
/// Push an additional string to the array.
pub fn push(&mut self, item: CString) {
let argc = self.ptrs.len() - 1;
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@asder8215 asder8215 Apr 25, 2026 •
edited by rustbot
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Out of curiosity, is it possible for self.ptrs.len() to be 0/should we be worried about underflow here?

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@joboet joboet Apr 25, 2026

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No, since there is always at least one element (the null terminator) in the array.

// Replace the null pointer at the end of the array...
self.ptrs[argc] = item.into_raw();
// ... and recreate it to restore the data structure invariant.
// Amend the array by another null pointer first, to ensure that the
// array is null-terminated even when the `push` panics, in which case
// the array will be left undisturbed (see #155748).
self.ptrs.push(ptr::null());
// Now, replace the previous null pointer.
self.ptrs[argc] = item.into_raw();
}

/// Returns a pointer to the C-string array managed by this type.
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