[PATCH] D37410: LTO: Try to open cache files before renaming them.

[Peter Collingbourne via Phabricator via llvm-commits]

pcc created this revision.
Herald added subscribers: hiraditya, inglorion, emaste.

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.

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


https://reviews.llvm.org/D37410

Files:
  lld/ELF/LTO.cpp
  llvm/include/llvm/LTO/Caching.h
  llvm/lib/LTO/Caching.cpp
  llvm/tools/gold/gold-plugin.cpp
  llvm/tools/llvm-lto2/llvm-lto2.cpp

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