Rollup merge of rust-lang#128977 - jieyouxu:writable-file, r=Kobzol

Only try to modify file times of a writable file

- First commit fixes a failure that I was running into locally trying to build a stage 1 `./x build library --stage 1` on windows due to trying to modify file times of a read-only file.
- Second commit introduces a `set_file_times` helper which opens a given path as a file in r+w mode and then sets file times. This should hopefully make setting file times less error prone, since trying to set file times on read-only file also happened in rust-lang#127850. (And apparently it only fails locally on Windows or something weird like that.)

src/bootstrap/src/core/download.rs

@@ -703,9 +703,7 @@ download-rustc = false
             let file_times = fs::FileTimes::new().set_accessed(now).set_modified(now);
 
             let llvm_config = llvm_root.join("bin").join(exe("llvm-config", self.build));
-            let llvm_config_file = t!(File::options().write(true).open(llvm_config));
-
-            t!(llvm_config_file.set_times(file_times));
+            t!(crate::utils::helpers::set_file_times(llvm_config, file_times));
 
             if self.should_fix_bins_and_dylibs() {
                 let llvm_lib = llvm_root.join("lib");

src/bootstrap/src/lib.rs

@@ -37,7 +37,9 @@ use crate::core::builder;
 use crate::core::builder::{Builder, Kind};
 use crate::core::config::{flags, DryRun, LldMode, LlvmLibunwind, Target, TargetSelection};
 use crate::utils::exec::{command, BehaviorOnFailure, BootstrapCommand, CommandOutput, OutputMode};
-use crate::utils::helpers::{self, dir_is_empty, exe, libdir, mtime, output, symlink_dir};
+use crate::utils::helpers::{
+    self, dir_is_empty, exe, libdir, mtime, output, set_file_times, symlink_dir,
+};
 
 mod core;
 mod utils;
@@ -1777,9 +1779,8 @@ Executed at: {executed_at}"#,
             }
         }
         if let Ok(()) = fs::hard_link(&src, dst) {
-            // Attempt to "easy copy" by creating a hard link
-            // (symlinks don't work on windows), but if that fails
-            // just fall back to a slow `copy` operation.
+            // Attempt to "easy copy" by creating a hard link (symlinks are priviledged on windows),
+            // but if that fails just fall back to a slow `copy` operation.
         } else {
             if let Err(e) = fs::copy(&src, dst) {
                 panic!("failed to copy `{}` to `{}`: {}", src.display(), dst.display(), e)
@@ -1790,8 +1791,7 @@ Executed at: {executed_at}"#,
                 .set_accessed(t!(metadata.accessed()))
                 .set_modified(t!(metadata.modified()));
 
-            let dst_file = t!(fs::File::open(dst));
-            t!(dst_file.set_times(file_times));
+            t!(set_file_times(dst, file_times));
         }
     }
 

src/bootstrap/src/utils/helpers.rs

@@ -544,3 +544,9 @@ pub fn get_closest_merge_base_commit(
 
     Ok(output_result(git.as_command_mut())?.trim().to_owned())
 }
+
+/// Sets the file times for a given file at `path`.
+pub fn set_file_times<P: AsRef<Path>>(path: P, times: fs::FileTimes) -> io::Result<()> {
+    let f = fs::File::options().write(true).open(path)?;
+    f.set_times(times)
+}

src/bootstrap/src/utils/helpers/tests.rs

@@ -3,7 +3,8 @@ use std::io::Write;
 use std::path::PathBuf;
 
 use crate::utils::helpers::{
-    check_cfg_arg, extract_beta_rev, hex_encode, make, program_out_of_date, symlink_dir,
+    check_cfg_arg, extract_beta_rev, hex_encode, make, program_out_of_date, set_file_times,
+    symlink_dir,
 };
 use crate::Config;
 
@@ -90,3 +91,20 @@ fn test_symlink_dir() {
     #[cfg(not(windows))]
     fs::remove_file(link_path).unwrap();
 }
+
+#[test]
+fn test_set_file_times_sanity_check() {
+    let config = Config::parse(&["check".to_owned(), "--config=/does/not/exist".to_owned()]);
+    let tempfile = config.tempdir().join(".tmp-file");
+
+    {
+        File::create(&tempfile).unwrap().write_all(b"dummy value").unwrap();
+        assert!(tempfile.exists());
+    }
+
+    // This might only fail on Windows (if file is default read-only then we try to modify file
+    // times).
+    let now = std::time::SystemTime::now();
+    let file_times = fs::FileTimes::new().set_accessed(now).set_modified(now);
+    set_file_times(&tempfile, file_times).unwrap();
+}