From a1c261cd096c9c2ebfffa7049e29c06914784c04 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sat, 5 Feb 2022 14:42:56 -0500
Subject: [PATCH] Store rlink data in opaque binary format on disk

---
 compiler/rustc_driver/src/lib.rs        | 8 +++++---
 compiler/rustc_interface/src/queries.rs | 9 +++------
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/compiler/rustc_driver/src/lib.rs b/compiler/rustc_driver/src/lib.rs
index acf221a08eeb2..ca4e7b5142ee7 100644
--- a/compiler/rustc_driver/src/lib.rs
+++ b/compiler/rustc_driver/src/lib.rs
@@ -29,7 +29,7 @@ use rustc_log::stdout_isatty;
 use rustc_metadata::locator;
 use rustc_save_analysis as save;
 use rustc_save_analysis::DumpHandler;
-use rustc_serialize::json::{self, ToJson};
+use rustc_serialize::json::ToJson;
 use rustc_session::config::{nightly_options, CG_OPTIONS, DB_OPTIONS};
 use rustc_session::config::{ErrorOutputType, Input, OutputType, PrintRequest, TrimmedDefPaths};
 use rustc_session::cstore::MetadataLoader;
@@ -595,10 +595,12 @@ impl RustcDefaultCalls {
                 // FIXME: #![crate_type] and #![crate_name] support not implemented yet
                 sess.init_crate_types(collect_crate_types(sess, &[]));
                 let outputs = compiler.build_output_filenames(sess, &[]);
-                let rlink_data = fs::read_to_string(file).unwrap_or_else(|err| {
+                let rlink_data = fs::read(file).unwrap_or_else(|err| {
                     sess.fatal(&format!("failed to read rlink file: {}", err));
                 });
-                let codegen_results: CodegenResults = json::decode(&rlink_data);
+                let mut decoder = rustc_serialize::opaque::Decoder::new(&rlink_data, 0);
+                let codegen_results: CodegenResults =
+                    rustc_serialize::Decodable::decode(&mut decoder);
                 let result = compiler.codegen_backend().link(sess, codegen_results, &outputs);
                 abort_on_err(result, sess);
             } else {
diff --git a/compiler/rustc_interface/src/queries.rs b/compiler/rustc_interface/src/queries.rs
index e635ee1e0ec8a..2640a9575a371 100644
--- a/compiler/rustc_interface/src/queries.rs
+++ b/compiler/rustc_interface/src/queries.rs
@@ -13,7 +13,6 @@ use rustc_middle::arena::Arena;
 use rustc_middle::dep_graph::DepGraph;
 use rustc_middle::ty::{GlobalCtxt, TyCtxt};
 use rustc_query_impl::Queries as TcxQueries;
-use rustc_serialize::json;
 use rustc_session::config::{self, OutputFilenames, OutputType};
 use rustc_session::{output::find_crate_name, Session};
 use rustc_span::symbol::sym;
@@ -367,12 +366,10 @@ impl Linker {
         }
 
         if sess.opts.debugging_opts.no_link {
-            // FIXME: use a binary format to encode the `.rlink` file
-            let rlink_data = json::encode(&codegen_results).map_err(|err| {
-                sess.fatal(&format!("failed to encode rlink: {}", err));
-            })?;
+            let mut encoder = rustc_serialize::opaque::Encoder::new(Vec::new());
+            rustc_serialize::Encodable::encode(&codegen_results, &mut encoder).unwrap();
             let rlink_file = self.prepare_outputs.with_extension(config::RLINK_EXT);
-            std::fs::write(&rlink_file, rlink_data).map_err(|err| {
+            std::fs::write(&rlink_file, encoder.into_inner()).map_err(|err| {
                 sess.fatal(&format!("failed to write file {}: {}", rlink_file.display(), err));
             })?;
             return Ok(());