rishi/scryer-prolog
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rework some unsafe parts

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- removed some unsafe
- added some safety comments
- add explicit types to transmute calls
- reworked UntypedArenaPtr -> TypedArenaPtr conversion

might help with mthom/scryer-prolog#2438, I noticed fewer complains from miri after changing the default impl for `ArenaAllocated::alloc`
This commit is contained in:
Bennet Bleßmann
2024-07-05 23:45:02 +02:00
parent a93585080c
commit dd2548453b
5 changed files with 102 additions and 116 deletions
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53
src/macros.rs
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@@ -173,13 +173,15 @@ macro_rules! typed_arena_ptr_as_cell {
macro_rules! raw_ptr_as_cell {
($ptr:expr) => {
// Cell is 64-bit, but raw ptr is 32-bit in 32-bit systems
HeapCellValue::from_raw_ptr_bytes(unsafe { std::mem::transmute($ptr) })
// TODO use <*{const,mut} _>::addr instead of as when the strict_provenance feature is stable rust-lang/rust#95228
// we might need <*{const,mut} _>::expose_provenance for strict provenance, dependening on how we recreate a pointer later
HeapCellValue::from_raw_ptr_bytes(($ptr as usize).to_ne_bytes())
};
}
macro_rules! untyped_arena_ptr_as_cell {
($ptr:expr) => {
HeapCellValue::from_bytes(unsafe { std::mem::transmute($ptr) })
HeapCellValue::from_bytes(UntypedArenaPtr::into_bytes($ptr))
};
}
@@ -224,86 +226,69 @@ macro_rules! stream_as_cell {
macro_rules! cell_as_stream {
($cell:expr) => {{
let ptr = cell_as_untyped_arena_ptr!($cell);
Stream::from_tag(ptr.get_tag(), ptr.payload_offset())
Stream::from_tag(ptr.get_tag(), ptr)
}};
}
macro_rules! cell_as_load_state_payload {
($cell:expr) => {
unsafe {
let ptr = cell_as_untyped_arena_ptr!($cell);
let ptr = std::mem::transmute::<_, *mut LiveLoadState>(ptr.payload_offset());
TypedArenaPtr::new(ptr)
}
};
($cell:expr) => {{
let ptr = cell_as_untyped_arena_ptr!($cell);
unsafe { ptr.as_typed_ptr::<LiveLoadState>() }
}};
}
macro_rules! match_untyped_arena_ptr_pat_body {
($ptr:ident, Integer, $n:ident, $code:expr) => {{
let payload_ptr = unsafe { std::mem::transmute::<_, *mut Integer>($ptr.payload_offset()) };
let $n = TypedArenaPtr::new(payload_ptr);
let $n = unsafe { $ptr.as_typed_ptr::<Integer>() };
#[allow(unused_braces)]
$code
}};
($ptr:ident, Rational, $n:ident, $code:expr) => {{
let payload_ptr = unsafe { std::mem::transmute::<_, *mut Rational>($ptr.payload_offset()) };
let $n = TypedArenaPtr::new(payload_ptr);
let $n = unsafe { $ptr.as_typed_ptr::<Rational>() };
#[allow(unused_braces)]
$code
}};
($ptr:ident, OssifiedOpDir, $n:ident, $code:expr) => {{
let payload_ptr =
unsafe { std::mem::transmute::<_, *mut OssifiedOpDir>($ptr.payload_offset()) };
let $n = TypedArenaPtr::new(payload_ptr);
let $n = unsafe { $ptr.as_typed_ptr::<OssifiedOpDir>() };
#[allow(unused_braces)]
$code
}};
($ptr:ident, LiveLoadState, $n:ident, $code:expr) => {{
let payload_ptr =
unsafe { std::mem::transmute::<_, *mut LiveLoadState>($ptr.payload_offset()) };
let $n = TypedArenaPtr::new(payload_ptr);
let $n = unsafe { $ptr.as_typed_ptr::<LiveLoadState>() };
#[allow(unused_braces)]
$code
}};
($ptr:ident, Stream, $s:ident, $code:expr) => {{
let $s = Stream::from_tag($ptr.get_tag(), $ptr.payload_offset());
let $s = Stream::from_tag($ptr.get_tag(), $ptr);
#[allow(unused_braces)]
$code
}};
($ptr:ident, TcpListener, $listener:ident, $code:expr) => {{
let payload_ptr =
unsafe { std::mem::transmute::<_, *mut TcpListener>($ptr.payload_offset()) };
#[allow(unused_mut)]
let mut $listener = TypedArenaPtr::new(payload_ptr);
let mut $listener = unsafe { $ptr.as_typed_ptr::<TcpListener>() };
#[allow(unused_braces)]
$code
}};
($ptr:ident, HttpListener, $listener:ident, $code:expr) => {{
let payload_ptr =
unsafe { std::mem::transmute::<_, *mut HttpListener>($ptr.payload_offset()) };
#[allow(unused_mut)]
let mut $listener = TypedArenaPtr::new(payload_ptr);
let mut $listener = unsafe { $ptr.as_typed_ptr::<HttpListener>() };
#[allow(unused_braces)]
$code
}};
($ptr:ident, HttpResponse, $listener:ident, $code:expr) => {{
let payload_ptr =
unsafe { std::mem::transmute::<_, *mut HttpResponse>($ptr.payload_offset()) };
#[allow(unused_mut)]
let mut $listener = TypedArenaPtr::new(payload_ptr);
let mut $listener = unsafe { $ptr.as_typed_ptr::<HttpResponse>() };
#[allow(unused_braces)]
$code
}};
($ptr:ident, IndexPtr, $ip:ident, $code:expr) => {{
#[allow(unused_mut)]
let mut $ip =
TypedArenaPtr::new(unsafe { std::mem::transmute::<_, *mut IndexPtr>($ptr.get_ptr()) });
let mut $ip = unsafe { $ptr.as_typed_ptr::<IndexPtr>() };
#[allow(unused_braces)]
$code
}};
($ptr:ident, $($tags:tt)|+, $s:ident, $code:expr) => {{
let $s = Stream::from_tag($ptr.get_tag(), $ptr.payload_offset());
let $s = Stream::from_tag($ptr.get_tag(), $ptr);
#[allow(unused_braces)]
$code
}};