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Clean up the API for opening/checking incremental-compilation files

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Returning dedicated structs and enums makes the meaning of each return value
more obvious, and provides a more natural home for documentation.

The intermediate `load_data` function was unhelpful, and has been inlined into
the main function.
This commit is contained in:
Zalathar
2026-03-25 21:23:16 +11:00
parent 23903d01c2
commit a7fa2dfd8e
2 changed files with 77 additions and 70 deletions
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compiler/rustc_incremental/src/persist/file_format.rs
+60 -38
View File
@@ -33,7 +33,7 @@ pub(crate) fn write_file_header(stream: &mut FileEncoder, sess: &Session) {
stream
.emit_raw_bytes(&[(HEADER_FORMAT_VERSION >> 0) as u8, (HEADER_FORMAT_VERSION >> 8) as u8]);
let rustc_version = rustc_version(sess.is_nightly_build(), sess.cfg_version);
let rustc_version = rustc_version(sess);
assert_eq!(rustc_version.len(), (rustc_version.len() as u8) as usize);
stream.emit_raw_bytes(&[rustc_version.len() as u8]);
stream.emit_raw_bytes(rustc_version.as_bytes());
@@ -80,26 +80,47 @@ pub(crate) fn save_in<F>(sess: &Session, path_buf: PathBuf, name: &str, encode:
}
}
/// Reads the contents of a file with a file header as defined in this module.
///
/// - Returns `Ok(Some(data, pos))` if the file existed and was generated by a
/// compatible compiler version. `data` is the entire contents of the file
/// and `pos` points to the first byte after the header.
/// - Returns `Ok(None)` if the file did not exist or was generated by an
/// incompatible version of the compiler.
/// - Returns `Err(..)` if some kind of IO error occurred while reading the
/// file.
pub(crate) fn read_file(
pub(crate) struct OpenFile {
/// A read-only mmap view of the file contents.
pub(crate) mmap: Mmap,
/// File position to start reading normal data from, just after the end of the file header.
pub(crate) start_pos: usize,
}
pub(crate) enum OpenFileError {
/// Either the file was not found, or one of the header checks failed.
///
/// These conditions prevent us from reading the file contents, but should
/// not trigger an error or even a warning, because they routinely happen
/// during normal operation:
/// - File-not-found occurs in a fresh build, or after clearing the build directory.
/// - Header-mismatch occurs after upgrading or switching compiler versions.
NotFoundOrHeaderMismatch,
/// An unexpected I/O error occurred while opening or checking the file.
IoError { err: io::Error },
}
impl From<io::Error> for OpenFileError {
fn from(err: io::Error) -> Self {
OpenFileError::IoError { err }
}
}
/// Tries to open a file that was written by the previous incremental-compilation
/// session, and checks that it was produced by a matching compiler version.
pub(crate) fn open_incremental_file(
sess: &Session,
path: &Path,
report_incremental_info: bool,
is_nightly_build: bool,
cfg_version: &'static str,
) -> io::Result<Option<(Mmap, usize)>> {
let file = match fs::File::open(path) {
Ok(file) => file,
Err(err) if err.kind() == io::ErrorKind::NotFound => return Ok(None),
Err(err) => return Err(err),
};
) -> Result<OpenFile, OpenFileError> {
let file = fs::File::open(path).map_err(|err| {
if err.kind() == io::ErrorKind::NotFound {
OpenFileError::NotFoundOrHeaderMismatch
} else {
OpenFileError::IoError { err }
}
})?;
// SAFETY: This process must not modify nor remove the backing file while the memory map lives.
// For the dep-graph and the work product index, it is as soon as the decoding is done.
// For the query result cache, the memory map is dropped in save_dep_graph before calling
@@ -116,8 +137,8 @@ pub(crate) fn read_file(
let mut file_magic = [0u8; 4];
file.read_exact(&mut file_magic)?;
if file_magic != FILE_MAGIC {
report_format_mismatch(report_incremental_info, path, "Wrong FILE_MAGIC");
return Ok(None);
report_format_mismatch(sess, path, "Wrong FILE_MAGIC");
return Err(OpenFileError::NotFoundOrHeaderMismatch);
}
}
@@ -130,8 +151,8 @@ pub(crate) fn read_file(
(header_format_version[0] as u16) | ((header_format_version[1] as u16) << 8);
if header_format_version != HEADER_FORMAT_VERSION {
report_format_mismatch(report_incremental_info, path, "Wrong HEADER_FORMAT_VERSION");
return Ok(None);
report_format_mismatch(sess, path, "Wrong HEADER_FORMAT_VERSION");
return Err(OpenFileError::NotFoundOrHeaderMismatch);
}
}
@@ -143,20 +164,20 @@ pub(crate) fn read_file(
let mut buffer = vec![0; rustc_version_str_len];
file.read_exact(&mut buffer)?;
if buffer != rustc_version(is_nightly_build, cfg_version).as_bytes() {
report_format_mismatch(report_incremental_info, path, "Different compiler version");
return Ok(None);
if buffer != rustc_version(sess).as_bytes() {
report_format_mismatch(sess, path, "Different compiler version");
return Err(OpenFileError::NotFoundOrHeaderMismatch);
}
}
let post_header_start_pos = file.position() as usize;
Ok(Some((mmap, post_header_start_pos)))
let start_pos = file.position() as usize;
Ok(OpenFile { mmap, start_pos })
}
fn report_format_mismatch(report_incremental_info: bool, file: &Path, message: &str) {
fn report_format_mismatch(sess: &Session, file: &Path, message: &str) {
debug!("read_file: {}", message);
if report_incremental_info {
if sess.opts.unstable_opts.incremental_info {
eprintln!(
"[incremental] ignoring cache artifact `{}`: {}",
file.file_name().unwrap().to_string_lossy(),
@@ -168,12 +189,13 @@ fn report_format_mismatch(report_incremental_info: bool, file: &Path, message: &
/// A version string that hopefully is always different for compiler versions
/// with different encodings of incremental compilation artifacts. Contains
/// the Git commit hash.
fn rustc_version(nightly_build: bool, cfg_version: &'static str) -> Cow<'static, str> {
if nightly_build {
if let Ok(val) = env::var("RUSTC_FORCE_RUSTC_VERSION") {
return val.into();
}
fn rustc_version(sess: &Session) -> Cow<'static, str> {
// Allow version string overrides so that tests can produce a header-mismatch on demand.
if sess.is_nightly_build()
&& let Ok(env_version) = env::var("RUSTC_FORCE_RUSTC_VERSION")
{
Cow::Owned(env_version)
} else {
Cow::Borrowed(sess.cfg_version)
}
cfg_version.into()
}
compiler/rustc_incremental/src/persist/load.rs
+17 -32
View File
@@ -1,9 +1,8 @@
//! Code to load the dep-graph from files.
use std::path::{Path, PathBuf};
use std::path::PathBuf;
use std::sync::Arc;
use rustc_data_structures::memmap::Mmap;
use rustc_data_structures::unord::UnordMap;
use rustc_hashes::Hash64;
use rustc_middle::dep_graph::{DepGraph, SerializedDepGraph, WorkProductMap};
@@ -20,6 +19,7 @@
use super::save::build_dep_graph;
use super::{file_format, work_product};
use crate::errors;
use crate::persist::file_format::{OpenFile, OpenFileError};
#[derive(Debug)]
/// Represents the result of an attempt to load incremental compilation data.
@@ -69,23 +69,6 @@ pub fn open(self, sess: &Session) -> T {
}
}
fn load_data(path: &Path, sess: &Session) -> LoadResult<(Mmap, usize)> {
match file_format::read_file(
path,
sess.opts.unstable_opts.incremental_info,
sess.is_nightly_build(),
sess.cfg_version,
) {
Ok(Some(data_and_pos)) => LoadResult::Ok { data: data_and_pos },
Ok(None) => {
// The file either didn't exist or was produced by an incompatible
// compiler version. Neither is an error.
LoadResult::DataOutOfDate
}
Err(err) => LoadResult::LoadDepGraph(path.to_path_buf(), err),
}
}
fn delete_dirty_work_product(sess: &Session, swp: SerializedWorkProduct) {
debug!("delete_dirty_work_product({:?})", swp);
work_product::delete_workproduct_files(sess, &swp.work_product);
@@ -113,12 +96,12 @@ fn load_dep_graph(sess: &Session) -> LoadResult<(Arc<SerializedDepGraph>, WorkPr
// when trying to load work products.
if sess.incr_comp_session_dir_opt().is_some() {
let work_products_path = work_products_path(sess);
let load_result = load_data(&work_products_path, sess);
if let LoadResult::Ok { data: (work_products_data, start_pos) } = load_result {
if let Ok(OpenFile { mmap, start_pos }) =
file_format::open_incremental_file(sess, &work_products_path)
{
// Decode the list of work_products
let Ok(mut work_product_decoder) = MemDecoder::new(&work_products_data[..], start_pos)
else {
let Ok(mut work_product_decoder) = MemDecoder::new(&mmap[..], start_pos) else {
sess.dcx().emit_warn(errors::CorruptFile { path: &work_products_path });
return LoadResult::DataOutOfDate;
};
@@ -147,11 +130,11 @@ fn load_dep_graph(sess: &Session) -> LoadResult<(Arc<SerializedDepGraph>, WorkPr
let _prof_timer = prof.generic_activity("incr_comp_load_dep_graph");
match load_data(&path, sess) {
LoadResult::DataOutOfDate => LoadResult::DataOutOfDate,
LoadResult::LoadDepGraph(path, err) => LoadResult::LoadDepGraph(path, err),
LoadResult::Ok { data: (bytes, start_pos) } => {
let Ok(mut decoder) = MemDecoder::new(&bytes, start_pos) else {
match file_format::open_incremental_file(sess, &path) {
Err(OpenFileError::NotFoundOrHeaderMismatch) => LoadResult::DataOutOfDate,
Err(OpenFileError::IoError { err }) => LoadResult::LoadDepGraph(path.to_owned(), err),
Ok(OpenFile { mmap, start_pos }) => {
let Ok(mut decoder) = MemDecoder::new(&mmap, start_pos) else {
sess.dcx().emit_warn(errors::CorruptFile { path: &path });
return LoadResult::DataOutOfDate;
};
@@ -191,15 +174,17 @@ pub fn load_query_result_cache(sess: &Session) -> Option<OnDiskCache> {
let _prof_timer = sess.prof.generic_activity("incr_comp_load_query_result_cache");
let path = query_cache_path(sess);
match load_data(&path, sess) {
LoadResult::Ok { data: (bytes, start_pos) } => {
let cache = OnDiskCache::new(sess, bytes, start_pos).unwrap_or_else(|()| {
match file_format::open_incremental_file(sess, &path) {
Ok(OpenFile { mmap, start_pos }) => {
let cache = OnDiskCache::new(sess, mmap, start_pos).unwrap_or_else(|()| {
sess.dcx().emit_warn(errors::CorruptFile { path: &path });
OnDiskCache::new_empty()
});
Some(cache)
}
_ => Some(OnDiskCache::new_empty()),
Err(OpenFileError::NotFoundOrHeaderMismatch | OpenFileError::IoError { .. }) => {
Some(OnDiskCache::new_empty())
}
}
}