Prepend temp files with a string per invocation of rustc

3 files changed, 50 insertions, 8 deletions

diff --git a/compiler/rustc_session/Cargo.toml b/compiler/rustc_session/Cargo.toml
index a087725d34d..63772a32222 100644
--- a/compiler/rustc_session/Cargo.toml
+++ b/compiler/rustc_session/Cargo.toml
@@ -7,6 +7,7 @@ edition = "2024"
 # tidy-alphabetical-start
 bitflags = "2.4.1"
 getopts = "0.2"
+rand = "0.9.0"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 946b1201e05..bdd54a15147 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -1016,10 +1016,13 @@ impl OutFileName {
         outputs: &OutputFilenames,
         flavor: OutputType,
         codegen_unit_name: &str,
+        invocation_temp: Option<&str>,
     ) -> PathBuf {
         match *self {
             OutFileName::Real(ref path) => path.clone(),
-            OutFileName::Stdout => outputs.temp_path_for_cgu(flavor, codegen_unit_name),
+            OutFileName::Stdout => {
+                outputs.temp_path_for_cgu(flavor, codegen_unit_name, invocation_temp)
+            }
         }
     }
 
@@ -1094,21 +1097,41 @@ impl OutputFilenames {
     /// Gets the path where a compilation artifact of the given type for the
     /// given codegen unit should be placed on disk. If codegen_unit_name is
     /// None, a path distinct from those of any codegen unit will be generated.
-    pub fn temp_path_for_cgu(&self, flavor: OutputType, codegen_unit_name: &str) -> PathBuf {
+    pub fn temp_path_for_cgu(
+        &self,
+        flavor: OutputType,
+        codegen_unit_name: &str,
+        invocation_temp: Option<&str>,
+    ) -> PathBuf {
         let extension = flavor.extension();
-        self.temp_path_ext_for_cgu(extension, codegen_unit_name)
+        self.temp_path_ext_for_cgu(extension, codegen_unit_name, invocation_temp)
     }
 
     /// Like `temp_path`, but specifically for dwarf objects.
-    pub fn temp_path_dwo_for_cgu(&self, codegen_unit_name: &str) -> PathBuf {
-        self.temp_path_ext_for_cgu(DWARF_OBJECT_EXT, codegen_unit_name)
+    pub fn temp_path_dwo_for_cgu(
+        &self,
+        codegen_unit_name: &str,
+        invocation_temp: Option<&str>,
+    ) -> PathBuf {
+        self.temp_path_ext_for_cgu(DWARF_OBJECT_EXT, codegen_unit_name, invocation_temp)
     }
 
     /// Like `temp_path`, but also supports things where there is no corresponding
     /// OutputType, like noopt-bitcode or lto-bitcode.
-    pub fn temp_path_ext_for_cgu(&self, ext: &str, codegen_unit_name: &str) -> PathBuf {
+    pub fn temp_path_ext_for_cgu(
+        &self,
+        ext: &str,
+        codegen_unit_name: &str,
+        invocation_temp: Option<&str>,
+    ) -> PathBuf {
         let mut extension = codegen_unit_name.to_string();
 
+        // Append `.{invocation_temp}` to ensure temporary files are unique.
+        if let Some(rng) = invocation_temp {
+            extension.push('.');
+            extension.push_str(rng);
+        }
+
         // FIXME: This is sketchy that we're not appending `.rcgu` when the ext is empty.
         // Append `.rcgu.{ext}`.
         if !ext.is_empty() {
@@ -1144,9 +1167,10 @@ impl OutputFilenames {
         split_debuginfo_kind: SplitDebuginfo,
         split_dwarf_kind: SplitDwarfKind,
         cgu_name: &str,
+        invocation_temp: Option<&str>,
     ) -> Option<PathBuf> {
-        let obj_out = self.temp_path_for_cgu(OutputType::Object, cgu_name);
-        let dwo_out = self.temp_path_dwo_for_cgu(cgu_name);
+        let obj_out = self.temp_path_for_cgu(OutputType::Object, cgu_name, invocation_temp);
+        let dwo_out = self.temp_path_dwo_for_cgu(cgu_name, invocation_temp);
         match (split_debuginfo_kind, split_dwarf_kind) {
             (SplitDebuginfo::Off, SplitDwarfKind::Single | SplitDwarfKind::Split) => None,
             // Single mode doesn't change how DWARF is emitted, but does add Split DWARF attributes
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index fb4a437a487..1359f7eb7bb 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -6,6 +6,8 @@ use std::sync::Arc;
 use std::sync::atomic::AtomicBool;
 use std::{env, fmt, io};
 
+use rand::{RngCore, rng};
+use rustc_data_structures::base_n::{CASE_INSENSITIVE, ToBaseN};
 use rustc_data_structures::flock;
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::profiling::{SelfProfiler, SelfProfilerRef};
@@ -203,6 +205,14 @@ pub struct Session {
 
     target_filesearch: FileSearch,
     host_filesearch: FileSearch,
+
+    /// A random string generated per invocation of rustc.
+    ///
+    /// This is prepended to all temporary files so that they do not collide
+    /// during concurrent invocations of rustc, or past invocations that were
+    /// preserved with a flag like `-C save-temps`, since these files may be
+    /// hard linked.
+    pub invocation_temp: Option<String>,
 }
 
 #[derive(PartialEq, Eq, PartialOrd, Ord)]
@@ -1117,6 +1127,12 @@ pub fn build_session(
     let target_filesearch =
         filesearch::FileSearch::new(&sopts.search_paths, &target_tlib_path, &target);
     let host_filesearch = filesearch::FileSearch::new(&sopts.search_paths, &host_tlib_path, &host);
+
+    let invocation_temp = sopts
+        .incremental
+        .as_ref()
+        .map(|_| rng().next_u32().to_base_fixed_len(CASE_INSENSITIVE).to_string());
+
     let sess = Session {
         target,
         host,
@@ -1140,6 +1156,7 @@ pub fn build_session(
         expanded_args,
         target_filesearch,
         host_filesearch,
+        invocation_temp,
     };
 
     validate_commandline_args_with_session_available(&sess);