Call FileEncoder::finish in rmeta encoding

Author: saethlin

Diff for: Cargo.lock

@@ -4041,6 +4041,7 @@ dependencies = [
  "rustc_query_impl",
  "rustc_query_system",
  "rustc_resolve",
+ "rustc_serialize",
  "rustc_session",
  "rustc_span",
  "rustc_symbol_mangling",

Diff for: compiler/rustc_codegen_ssa/src/lib.rs

@@ -226,7 +226,7 @@ impl CodegenResults {
         encoder.emit_raw_bytes(&RLINK_VERSION.to_be_bytes());
         encoder.emit_str(sess.cfg_version);
         Encodable::encode(codegen_results, &mut encoder);
-        encoder.finish()
+        encoder.finish().map_err(|(_path, err)| err)
     }
 
     pub fn deserialize_rlink(sess: &Session, data: Vec<u8>) -> Result<Self, CodegenErrors> {

Diff for: compiler/rustc_incremental/src/persist/file_format.rs

@@ -80,8 +80,8 @@ where
             );
             debug!("save: data written to disk successfully");
         }
-        Err(err) => {
-            sess.emit_err(errors::WriteNew { name, path: path_buf, err });
+        Err((path, err)) => {
+            sess.emit_err(errors::WriteNew { name, path, err });
         }
     }
 }

Diff for: compiler/rustc_incremental/src/persist/save.rs

@@ -50,9 +50,6 @@ pub fn save_dep_graph(tcx: TyCtxt<'_>) {
         join(
             move || {
                 sess.time("incr_comp_persist_dep_graph", || {
-                    if let Err(err) = tcx.dep_graph.encode(&tcx.sess.prof) {
-                        sess.emit_err(errors::WriteDepGraph { path: &staging_dep_graph_path, err });
-                    }
                     if let Err(err) = fs::rename(&staging_dep_graph_path, &dep_graph_path) {
                         sess.emit_err(errors::MoveDepGraph {
                             from: &staging_dep_graph_path,

Diff for: compiler/rustc_interface/Cargo.toml

@@ -40,6 +40,7 @@ rustc_privacy = { path = "../rustc_privacy" }
 rustc_query_impl = { path = "../rustc_query_impl" }
 rustc_query_system = { path = "../rustc_query_system" }
 rustc_resolve = { path = "../rustc_resolve" }
+rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_symbol_mangling = { path = "../rustc_symbol_mangling" }

Diff for: compiler/rustc_interface/src/queries.rs

@@ -1,6 +1,6 @@
 use crate::errors::{FailedWritingFile, RustcErrorFatal, RustcErrorUnexpectedAnnotation};
 use crate::interface::{Compiler, Result};
-use crate::{passes, util};
+use crate::{errors, passes, util};
 
 use rustc_ast as ast;
 use rustc_codegen_ssa::traits::CodegenBackend;
@@ -15,6 +15,7 @@ use rustc_metadata::creader::CStore;
 use rustc_middle::arena::Arena;
 use rustc_middle::dep_graph::DepGraph;
 use rustc_middle::ty::{GlobalCtxt, TyCtxt};
+use rustc_serialize::opaque::FileEncodeResult;
 use rustc_session::config::{self, CrateType, OutputFilenames, OutputType};
 use rustc_session::cstore::Untracked;
 use rustc_session::output::find_crate_name;
@@ -102,6 +103,10 @@ impl<'tcx> Queries<'tcx> {
         }
     }
 
+    pub fn finish(&self) -> FileEncodeResult {
+        if let Some(gcx) = self.gcx_cell.get() { gcx.finish() } else { Ok(0) }
+    }
+
     pub fn parse(&self) -> Result<QueryResult<'_, ast::Crate>> {
         self.parse.compute(|| {
             passes::parse(&self.compiler.sess).map_err(|mut parse_error| parse_error.emit())
@@ -317,6 +322,9 @@ impl Compiler {
         // The timer's lifetime spans the dropping of `queries`, which contains
         // the global context.
         _timer = Some(self.sess.timer("free_global_ctxt"));
+        if let Err((path, error)) = queries.finish() {
+            self.sess.emit_err(errors::FailedWritingFile { path: &path, error });
+        }
 
         ret
     }

Diff for: compiler/rustc_metadata/messages.ftl

@@ -63,11 +63,8 @@ metadata_extern_location_not_file =
 metadata_fail_create_file_encoder =
     failed to create file encoder: {$err}
 
-metadata_fail_seek_file =
-    failed to seek the file: {$err}
-
 metadata_fail_write_file =
-    failed to write to the file: {$err}
+    failed to write to `{$path}`: {$err}
 
 metadata_failed_copy_to_stdout =
     failed to copy {$filename} to stdout: {$err}

Diff for: compiler/rustc_metadata/src/errors.rs

@@ -307,15 +307,10 @@ pub struct FailCreateFileEncoder {
     pub err: Error,
 }
 
-#[derive(Diagnostic)]
-#[diag(metadata_fail_seek_file)]
-pub struct FailSeekFile {
-    pub err: Error,
-}
-
 #[derive(Diagnostic)]
 #[diag(metadata_fail_write_file)]
-pub struct FailWriteFile {
+pub struct FailWriteFile<'a> {
+    pub path: &'a Path,
     pub err: Error,
 }
 

Diff for: compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1,4 +1,4 @@
-use crate::errors::{FailCreateFileEncoder, FailSeekFile, FailWriteFile};
+use crate::errors::{FailCreateFileEncoder, FailWriteFile};
 use crate::rmeta::def_path_hash_map::DefPathHashMapRef;
 use crate::rmeta::table::TableBuilder;
 use crate::rmeta::*;
@@ -42,6 +42,7 @@ use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{self, ExternalSource, FileName, SourceFile, Span, SpanData, SyntaxContext};
 use std::borrow::Borrow;
 use std::collections::hash_map::Entry;
+use std::fs::File;
 use std::hash::Hash;
 use std::io::{Read, Seek, Write};
 use std::num::NonZeroUsize;
@@ -2250,25 +2251,34 @@ fn encode_metadata_impl(tcx: TyCtxt<'_>, path: &Path) {
     // culminating in the `CrateRoot` which points to all of it.
     let root = ecx.encode_crate_root();
 
-    ecx.opaque.flush();
+    // Make sure we report any errors from writing to the file.
+    // If we forget this, compilation can succeed with an incomplete rmeta file,
+    // causing an ICE when the rmeta file is read by another compilation.
+    if let Err((path, err)) = ecx.opaque.finish() {
+        tcx.sess.emit_err(FailWriteFile { path: &path, err });
+    }
+
+    let file = ecx.opaque.file();
+    if let Err(err) = encode_root_position(file, root.position.get()) {
+        tcx.sess.emit_err(FailWriteFile { path: ecx.opaque.path(), err });
+    }
+
+    // Record metadata size for self-profiling
+    tcx.prof.artifact_size("crate_metadata", "crate_metadata", file.metadata().unwrap().len());
+}
 
-    let mut file = ecx.opaque.file();
+fn encode_root_position(mut file: &File, pos: usize) -> Result<(), std::io::Error> {
     // We will return to this position after writing the root position.
     let pos_before_seek = file.stream_position().unwrap();
 
     // Encode the root position.
     let header = METADATA_HEADER.len();
-    file.seek(std::io::SeekFrom::Start(header as u64))
-        .unwrap_or_else(|err| tcx.sess.emit_fatal(FailSeekFile { err }));
-    let pos = root.position.get();
-    file.write_all(&[(pos >> 24) as u8, (pos >> 16) as u8, (pos >> 8) as u8, (pos >> 0) as u8])
-        .unwrap_or_else(|err| tcx.sess.emit_fatal(FailWriteFile { err }));
+    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])?;
 
     // Return to the position where we are before writing the root position.
-    file.seek(std::io::SeekFrom::Start(pos_before_seek)).unwrap();
-
-    // Record metadata size for self-profiling
-    tcx.prof.artifact_size("crate_metadata", "crate_metadata", file.metadata().unwrap().len());
+    file.seek(std::io::SeekFrom::Start(pos_before_seek))?;
+    Ok(())
 }
 
 pub fn provide(providers: &mut Providers) {

Diff for: compiler/rustc_middle/src/query/on_disk_cache.rs

@@ -25,7 +25,6 @@ use rustc_span::source_map::{SourceMap, StableSourceFileId};
 use rustc_span::{BytePos, ExpnData, ExpnHash, Pos, RelativeBytePos, SourceFile, Span};
 use rustc_span::{CachingSourceMapView, Symbol};
 use std::collections::hash_map::Entry;
-use std::io;
 use std::mem;
 
 const TAG_FILE_FOOTER: u128 = 0xC0FFEE_C0FFEE_C0FFEE_C0FFEE_C0FFEE;
@@ -862,7 +861,7 @@ impl<'a, 'tcx> CacheEncoder<'a, 'tcx> {
     }
 
     #[inline]
-    fn finish(self) -> Result<usize, io::Error> {
+    fn finish(mut self) -> FileEncodeResult {
         self.encoder.finish()
     }
 }

Diff for: compiler/rustc_middle/src/ty/context.rs

@@ -597,6 +597,10 @@ impl<'tcx> GlobalCtxt<'tcx> {
         let icx = tls::ImplicitCtxt::new(self);
         tls::enter_context(&icx, || f(icx.tcx))
     }
+
+    pub fn finish(&self) -> FileEncodeResult {
+        self.dep_graph.finish_encoding(&self.sess.prof)
+    }
 }
 
 impl<'tcx> TyCtxt<'tcx> {

Diff for: compiler/rustc_query_system/src/dep_graph/graph.rs

@@ -982,7 +982,7 @@ impl<D: Deps> DepGraph<D> {
         }
     }
 
-    pub fn encode(&self, profiler: &SelfProfilerRef) -> FileEncodeResult {
+    pub fn finish_encoding(&self, profiler: &SelfProfilerRef) -> FileEncodeResult {
         if let Some(data) = &self.data {
             data.current.encoder.steal().finish(profiler)
         } else {

Diff for: compiler/rustc_serialize/src/opaque.rs

@@ -5,12 +5,13 @@ use std::io::{self, Write};
 use std::marker::PhantomData;
 use std::ops::Range;
 use std::path::Path;
+use std::path::PathBuf;
 
 // -----------------------------------------------------------------------------
 // Encoder
 // -----------------------------------------------------------------------------
 
-pub type FileEncodeResult = Result<usize, io::Error>;
+pub type FileEncodeResult = Result<usize, (PathBuf, io::Error)>;
 
 /// The size of the buffer in `FileEncoder`.
 const BUF_SIZE: usize = 8192;
@@ -34,21 +35,28 @@ pub struct FileEncoder {
     // This is used to implement delayed error handling, as described in the
     // comment on `trait Encoder`.
     res: Result<(), io::Error>,
+    path: PathBuf,
+    #[cfg(debug_assertions)]
+    finished: bool,
 }
 
 impl FileEncoder {
     pub fn new<P: AsRef<Path>>(path: P) -> io::Result<Self> {
         // File::create opens the file for writing only. When -Zmeta-stats is enabled, the metadata
         // encoder rewinds the file to inspect what was written. So we need to always open the file
         // for reading and writing.
-        let file = File::options().read(true).write(true).create(true).truncate(true).open(path)?;
+        let file =
+            File::options().read(true).write(true).create(true).truncate(true).open(&path)?;
 
         Ok(FileEncoder {
             buf: vec![0u8; BUF_SIZE].into_boxed_slice().try_into().unwrap(),
+            path: path.as_ref().into(),
             buffered: 0,
             flushed: 0,
             file,
             res: Ok(()),
+            #[cfg(debug_assertions)]
+            finished: false,
         })
     }
 
@@ -63,6 +71,10 @@ impl FileEncoder {
     #[cold]
     #[inline(never)]
     pub fn flush(&mut self) {
+        #[cfg(debug_assertions)]
+        {
+            self.finished = false;
+        }
         if self.res.is_ok() {
             self.res = self.file.write_all(&self.buf[..self.buffered]);
         }
@@ -74,6 +86,10 @@ impl FileEncoder {
         &self.file
     }
 
+    pub fn path(&self) -> &Path {
+        &self.path
+    }
+
     #[inline]
     fn buffer_empty(&mut self) -> &mut [u8] {
         // SAFETY: self.buffered is inbounds as an invariant of the type
@@ -97,6 +113,10 @@ impl FileEncoder {
 
     #[inline]
     fn write_all(&mut self, buf: &[u8]) {
+        #[cfg(debug_assertions)]
+        {
+            self.finished = false;
+        }
         if let Some(dest) = self.buffer_empty().get_mut(..buf.len()) {
             dest.copy_from_slice(buf);
             self.buffered += buf.len();
@@ -121,6 +141,10 @@ impl FileEncoder {
     /// with one instruction, so while this does in some sense do wasted work, we come out ahead.
     #[inline]
     pub fn write_with<const N: usize>(&mut self, visitor: impl FnOnce(&mut [u8; N]) -> usize) {
+        #[cfg(debug_assertions)]
+        {
+            self.finished = false;
+        }
         let flush_threshold = const { BUF_SIZE.checked_sub(N).unwrap() };
         if std::intrinsics::unlikely(self.buffered > flush_threshold) {
             self.flush();
@@ -152,20 +176,25 @@ impl FileEncoder {
         })
     }
 
-    pub fn finish(mut self) -> Result<usize, io::Error> {
+    pub fn finish(&mut self) -> FileEncodeResult {
         self.flush();
+        #[cfg(debug_assertions)]
+        {
+            self.finished = true;
+        }
         match std::mem::replace(&mut self.res, Ok(())) {
             Ok(()) => Ok(self.position()),
-            Err(e) => Err(e),
+            Err(e) => Err((self.path.clone(), e)),
         }
     }
 }
 
+#[cfg(debug_assertions)]
 impl Drop for FileEncoder {
     fn drop(&mut self) {
-        // Likely to be a no-op, because `finish` should have been called and
-        // it also flushes. But do it just in case.
-        self.flush();
+        if !std::thread::panicking() {
+            assert!(self.finished);
+        }
     }
 }
 

Diff for: src/librustdoc/scrape_examples.rs

@@ -325,7 +325,7 @@ pub(crate) fn run(
         // Save output to provided path
         let mut encoder = FileEncoder::new(options.output_path).map_err(|e| e.to_string())?;
         calls.encode(&mut encoder);
-        encoder.finish().map_err(|e| e.to_string())?;
+        encoder.finish().map_err(|(_path, e)| e.to_string())?;
 
         Ok(())
     };