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avoid writing to readonly refcounts

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Brendan Hansknecht 2024-12-28 14:43:17 -08:00
parent 9b13b19d08
commit ad41b509cf
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2 changed files with 16 additions and 4 deletions
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10
crates/roc_std/src/roc_list.rs
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@ -174,7 +174,10 @@ where
/// should be considered for marking read-only.
pub unsafe fn set_readonly(&mut self) {
if let Some((_, storage)) = self.elements_and_storage() {
storage.set(Storage::Readonly);
// Only safe to write to the pointer if it is not constant (0)
if !matches!(storage.get(), Storage::Readonly) {
storage.set(Storage::Readonly);
}
}
}
@ -676,7 +679,10 @@ where
let ptr = self.ptr_to_refcount();
unsafe {
let value = std::ptr::read(ptr);
std::ptr::write(ptr, Ord::max(0, ((value as isize) + 1) as usize));
// Only safe to write to the pointer if it is not constant (0)
if value != 0 {
std::ptr::write(ptr, (value as isize + 1) as usize);
}
}
}

10
crates/roc_std/src/roc_str.rs
View file

@ -943,14 +943,20 @@ impl BigString {
assert_ne!(self.capacity(), 0);
let ptr = self.ptr_to_refcount();
unsafe { std::ptr::write(ptr, 0) }
// Only safe to write to the pointer if it is not constant (0)
if unsafe { std::ptr::read(ptr) } != 0 {
unsafe { std::ptr::write(ptr, 0) }
}
}
fn inc(&mut self) {
let ptr = self.ptr_to_refcount();
unsafe {
let value = std::ptr::read(ptr);
std::ptr::write(ptr, Ord::max(0, ((value as isize) + 1) as usize));
// Only safe to write to the pointer if it is not constant (0)
if value != 0 {
std::ptr::write(ptr, (value as isize + 1) as usize);
}
}
}