[lld] r312567 - LTO: Try to open cache files before renaming them.

[Peter Collingbourne via llvm-commits]

Author: pcc
Date: Tue Sep  5 12:51:38 2017
New Revision: 312567

URL: http://llvm.org/viewvc/llvm-project?rev=312567&view=rev
Log:
LTO: Try to open cache files before renaming them.

It appears that a potential race between the cache client and the cache
pruner that I thought was unlikely actually happened in practice [1].
Try to avoid the race condition by opening the temporary file before
renaming it. Do this only on non-Windows platforms because we cannot
rename open files on Windows using the sys::fs::rename function.

[1] https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.memory%2FLinux_CFI%2F1610%2F%2B%2Frecipes%2Fsteps%2Fcompile%2F0%2Fstdout

Differential Revision: https://reviews.llvm.org/D37410

Modified:
    lld/trunk/ELF/LTO.cpp

Modified: lld/trunk/ELF/LTO.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LTO.cpp?rev=312567&r1=312566&r2=312567&view=diff
==============================================================================
--- lld/trunk/ELF/LTO.cpp (original)
+++ lld/trunk/ELF/LTO.cpp Tue Sep  5 12:51:38 2017
@@ -175,9 +175,8 @@ std::vector<InputFile *> BitcodeCompiler
   if (!Config->ThinLTOCacheDir.empty())
     Cache = check(
         lto::localCache(Config->ThinLTOCacheDir,
-                        [&](size_t Task, std::unique_ptr<MemoryBuffer> MB) {
-                          Files[Task] = std::move(MB);
-                        }));
+                        [&](size_t Task, std::unique_ptr<MemoryBuffer> MB,
+                            StringRef Path) { Files[Task] = std::move(MB); }));
 
   checkError(LTOObj->run(
       [&](size_t Task) {