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Auto merge of #118344 - saethlin:rmeta-header-pos, r=WaffleLapkin

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Use a u64 for the rmeta root position

Waffle noticed this in https://github.com/rust-lang/rust/pull/117301#discussion_r1405410174

We've upgraded the other file offsets to u64, and this one only costs 4 bytes per file. Also the way the truncation was being done before was extremely easy to miss, I sure missed it! It's not clear to me if not having this change effectively made the other upgrades from u32 to u64 ineffective, but we can have it now.

r? `@WaffleLapkin`
This commit is contained in:
bors 2023-12-11 17:21:14 +00:00
commit 57010939ed
6 changed files with 46 additions and 44 deletions
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8
compiler/rustc_metadata/src/locator.rs
View file

@ -783,8 +783,8 @@ fn get_metadata_section<'p>(
loader.get_dylib_metadata(target, filename).map_err(MetadataError::LoadFailure)?;
// The header is uncompressed
let header_len = METADATA_HEADER.len();
// header + u32 length of data
let data_start = header_len + 4;
// header + u64 length of data
let data_start = header_len + 8;
debug!("checking {} bytes of metadata-version stamp", header_len);
let header = &buf[..cmp::min(header_len, buf.len())];
@ -797,13 +797,13 @@ fn get_metadata_section<'p>(
// Length of the compressed stream - this allows linkers to pad the section if they want
let Ok(len_bytes) =
<[u8; 4]>::try_from(&buf[header_len..cmp::min(data_start, buf.len())])
<[u8; 8]>::try_from(&buf[header_len..cmp::min(data_start, buf.len())])
else {
return Err(MetadataError::LoadFailure(
"invalid metadata length found".to_string(),
));
};
let compressed_len = u32::from_be_bytes(len_bytes) as usize;
let compressed_len = u64::from_le_bytes(len_bytes) as usize;
// Header is okay -> inflate the actual metadata
let compressed_bytes = buf.slice(|buf| &buf[data_start..(data_start + compressed_len)]);

25
compiler/rustc_metadata/src/rmeta/decoder.rs
View file

@ -690,28 +690,25 @@ impl MetadataBlob {
}
pub(crate) fn get_rustc_version(&self) -> String {
LazyValue::<String>::from_position(NonZeroUsize::new(METADATA_HEADER.len() + 4).unwrap())
LazyValue::<String>::from_position(NonZeroUsize::new(METADATA_HEADER.len() + 8).unwrap())
.decode(self)
}
pub(crate) fn get_header(&self) -> CrateHeader {
let slice = &self.blob()[..];
fn root_pos(&self) -> NonZeroUsize {
let offset = METADATA_HEADER.len();
let pos_bytes = self.blob()[offset..][..8].try_into().unwrap();
let pos = u64::from_le_bytes(pos_bytes);
NonZeroUsize::new(pos as usize).unwrap()
}
let pos_bytes = slice[offset..][..4].try_into().unwrap();
let pos = u32::from_be_bytes(pos_bytes) as usize;
LazyValue::<CrateHeader>::from_position(NonZeroUsize::new(pos).unwrap()).decode(self)
pub(crate) fn get_header(&self) -> CrateHeader {
let pos = self.root_pos();
LazyValue::<CrateHeader>::from_position(pos).decode(self)
}
pub(crate) fn get_root(&self) -> CrateRoot {
let slice = &self.blob()[..];
let offset = METADATA_HEADER.len();
let pos_bytes = slice[offset..][..4].try_into().unwrap();
let pos = u32::from_be_bytes(pos_bytes) as usize;
LazyValue::<CrateRoot>::from_position(NonZeroUsize::new(pos).unwrap()).decode(self)
let pos = self.root_pos();
LazyValue::<CrateRoot>::from_position(pos).decode(self)
}
pub(crate) fn list_crate_metadata(

4
compiler/rustc_metadata/src/rmeta/encoder.rs
View file

@ -2190,7 +2190,7 @@ pub fn encode_metadata(tcx: TyCtxt<'_>, path: &Path) {
encoder.emit_raw_bytes(METADATA_HEADER);
// Will be filled with the root position after encoding everything.
encoder.emit_raw_bytes(&[0, 0, 0, 0]);
encoder.emit_raw_bytes(&0u64.to_le_bytes());
let source_map_files = tcx.sess.source_map().files();
let source_file_cache = (source_map_files[0].clone(), 0);
@ -2246,7 +2246,7 @@ fn encode_root_position(mut file: &File, pos: usize) -> Result<(), std::io::Erro
// Encode the root position.
let header = METADATA_HEADER.len();
file.seek(std::io::SeekFrom::Start(header as u64))?;
file.write_all(&[(pos >> 24) as u8, (pos >> 16) as u8, (pos >> 8) as u8, (pos >> 0) as u8])?;
file.write_all(&pos.to_le_bytes())?;
// Return to the position where we are before writing the root position.
file.seek(std::io::SeekFrom::Start(pos_before_seek))?;

4
compiler/rustc_metadata/src/rmeta/mod.rs
View file

@ -57,12 +57,12 @@ pub(crate) fn rustc_version(cfg_version: &'static str) -> String {
/// Metadata encoding version.
/// N.B., increment this if you change the format of metadata such that
/// the rustc version can't be found to compare with `rustc_version()`.
const METADATA_VERSION: u8 = 8;
const METADATA_VERSION: u8 = 9;
/// Metadata header which includes `METADATA_VERSION`.
///
/// This header is followed by the length of the compressed data, then
/// the position of the `CrateRoot`, which is encoded as a 32-bit big-endian
/// the position of the `CrateRoot`, which is encoded as a 64-bit little-endian
/// unsigned integer, and further followed by the rustc version string.
pub const METADATA_HEADER: &[u8] = &[b'r', b'u', b's', b't', 0, 0, 0, METADATA_VERSION];