bjoernager/rust
bjoernager/rust
1
Fork 0
Code Issues Pull requests Activity

Use delayed error handling for Encodable and Encoder infallible.

Browse source 
There are two impls of the `Encoder` trait: `opaque::Encoder` and
`opaque::FileEncoder`. The former encodes into memory and is infallible, the
latter writes to file and is fallible.

Currently, standard `Result`/`?`/`unwrap` error handling is used, but this is a
bit verbose and has non-trivial cost, which is annoying given how rare failures
are (especially in the infallible `opaque::Encoder` case).

This commit changes how `Encoder` fallibility is handled. All the `emit_*`
methods are now infallible. `opaque::Encoder` requires no great changes for
this. `opaque::FileEncoder` now implements a delayed error handling strategy.
If a failure occurs, it records this via the `res` field, and all subsequent
encoding operations are skipped if `res` indicates an error has occurred. Once
encoding is complete, the new `finish` method is called, which returns a
`Result`. In other words, there is now a single `Result`-producing method
instead of many of them.

This has very little effect on how any file errors are reported if
`opaque::FileEncoder` has any failures.

Much of this commit is boring mechanical changes, removing `Result` return
values and `?` or `unwrap` from expressions. The more interesting parts are as
follows.
- serialize.rs: The `Encoder` trait gains an `Ok` associated type. The
  `into_inner` method is changed into `finish`, which returns
  `Result<Vec<u8>, !>`.
- opaque.rs: The `FileEncoder` adopts the delayed error handling
  strategy. Its `Ok` type is a `usize`, returning the number of bytes
  written, replacing previous uses of `FileEncoder::position`.
- Various methods that take an encoder now consume it, rather than being
  passed a mutable reference, e.g. `serialize_query_result_cache`.
This commit is contained in:
Nicholas Nethercote 2022-06-07 13:30:45 +10:00
parent 582b9cbc45
commit 1acbe7573d
45 changed files with 611 additions and 682 deletions
Download patch file Download diff file Expand all files Collapse all files

12
compiler/rustc_codegen_ssa/src/lib.rs
View file

@ -29,7 +29,7 @@ use rustc_middle::dep_graph::WorkProduct;
use rustc_middle::middle::dependency_format::Dependencies;
use rustc_middle::middle::exported_symbols::SymbolExportKind;
use rustc_middle::ty::query::{ExternProviders, Providers};
use rustc_serialize::{opaque, Decodable, Decoder, Encoder};
use rustc_serialize::{opaque, Decodable, Decoder, Encodable, Encoder};
use rustc_session::config::{CrateType, OutputFilenames, OutputType, RUST_CGU_EXT};
use rustc_session::cstore::{self, CrateSource};
use rustc_session::utils::NativeLibKind;
@ -204,13 +204,13 @@ const RUSTC_VERSION: Option<&str> = option_env!("CFG_VERSION");
impl CodegenResults {
pub fn serialize_rlink(codegen_results: &CodegenResults) -> Vec<u8> {
let mut encoder = opaque::Encoder::new();
encoder.emit_raw_bytes(RLINK_MAGIC).unwrap();
encoder.emit_raw_bytes(RLINK_MAGIC);
// `emit_raw_bytes` is used to make sure that the version representation does not depend on
// Encoder's inner representation of `u32`.
encoder.emit_raw_bytes(&RLINK_VERSION.to_be_bytes()).unwrap();
encoder.emit_str(RUSTC_VERSION.unwrap()).unwrap();
rustc_serialize::Encodable::encode(codegen_results, &mut encoder).unwrap();
encoder.into_inner()
encoder.emit_raw_bytes(&RLINK_VERSION.to_be_bytes());
encoder.emit_str(RUSTC_VERSION.unwrap());
Encodable::encode(codegen_results, &mut encoder);
encoder.finish().unwrap()
}
pub fn deserialize_rlink(data: Vec<u8>) -> Result<Self, String> {