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add some comments for encode_and_write_metadata

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This commit is contained in:
Yoshiki Matsuda 2022-06-05 22:23:06 +09:00
parent 63dec941e1
commit ad55481043
1 changed files with 6 additions and 0 deletions
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6
compiler/rustc_metadata/src/fs.rs
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@ -69,6 +69,8 @@ pub fn encode_and_write_metadata(
let metadata_tmpdir = MaybeTempDir::new(metadata_tmpdir, tcx.sess.opts.cg.save_temps);
let metadata_filename = metadata_tmpdir.as_ref().join(METADATA_FILENAME);
// Always create a file at `metadata_filename`, even if we have nothing to write to it.
// This simplifies the creation of the output `out_filename` when requested.
match metadata_kind {
MetadataKind::None => {
std::fs::File::create(&metadata_filename).unwrap_or_else(|e| {
@ -86,6 +88,9 @@ pub fn encode_and_write_metadata(
let _prof_timer = tcx.sess.prof.generic_activity("write_crate_metadata");
// If the user requests metadata as output, rename `metadata_filename`
// to the expected output `out_filename`. The match above should ensure
// this file always exists.
let need_metadata_file = tcx.sess.opts.output_types.contains_key(&OutputType::Metadata);
let (metadata_filename, metadata_tmpdir) = if need_metadata_file {
if let Err(e) = non_durable_rename(&metadata_filename, &out_filename) {
@ -102,6 +107,7 @@ pub fn encode_and_write_metadata(
(metadata_filename, Some(metadata_tmpdir))
};
// Load metadata back to memory: codegen may need to include it in object files.
let metadata =
EncodedMetadata::from_path(metadata_filename, metadata_tmpdir).unwrap_or_else(|e| {
tcx.sess.fatal(&format!("failed to create encoded metadata from file: {}", e))