Move jobserver initialization before thread pool creation

Author: Mark-Simulacrum

Cargo.lock

@@ -3868,7 +3868,6 @@ dependencies = [
  "rustc_feature",
  "rustc_fs_util",
  "rustc_index",
- "rustc_jobserver",
  "rustc_target",
  "serialize",
  "syntax_pos",

src/librustc_interface/interface.rs

@@ -181,6 +181,20 @@ pub fn run_compiler_in_existing_thread_pool<R>(
 
 pub fn run_compiler<R: Send>(mut config: Config, f: impl FnOnce(&Compiler) -> R + Send) -> R {
     let stderr = config.stderr.take();
+
+    if config.opts.debugging_opts.jobserver_token_requests {
+        if let config::ErrorOutputType::Json { .. } = config.opts.error_format {
+            if stderr.is_some() {
+                panic!("Non-default output not supported with -Zjobserver-token-requests");
+            }
+        } else {
+            panic!("-Zjobserver-token-requests can only be specified if using \
+                JSON error output type");
+        }
+    }
+
+    rustc_jobserver::initialize(config.opts.debugging_opts.jobserver_token_requests);
+
     util::spawn_thread_pool(
         config.opts.edition,
         config.opts.debugging_opts.threads,

src/librustc_session/Cargo.toml

@@ -19,4 +19,3 @@ syntax_pos = { path = "../libsyntax_pos" }
 rustc_index = { path = "../librustc_index" }
 rustc_fs_util = { path = "../librustc_fs_util" }
 num_cpus = "1.0"
-rustc_jobserver = { path = "../librustc_jobserver" }

src/librustc_session/session.rs

@@ -1126,21 +1126,6 @@ fn build_session_(
         CguReuseTracker::new_disabled()
     };
 
-    if sopts.debugging_opts.jobserver_token_requests {
-        if let config::ErrorOutputType::Json { .. } = sopts.error_format {
-            if is_diagnostic_output_raw {
-                panic!("Raw output format not supported with -Zjobserver-token-requests");
-            }
-        } else {
-            parse_sess.span_diagnostic
-                .fatal("-Zjobserver-token-requests can only be specified if \
-                        using JSON error output type")
-                .raise();
-        }
-    }
-
-    rustc_jobserver::initialize(sopts.debugging_opts.jobserver_token_requests);
-
     let sess = Session {
         target: target_cfg,
         host,