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llvm-mirror/include/llvm/LTO/Caching.h
Peter Collingbourne 0ec5439ada 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

llvm-svn: 312567
2017-09-05 19:51:38 +00:00

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1.5 KiB
C++

//===- Caching.h - LLVM Link Time Optimizer Configuration -----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the localCache function, which allows clients to add a
// filesystem cache to ThinLTO.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LTO_CACHING_H
#define LLVM_LTO_CACHING_H
#include "llvm/LTO/LTO.h"
#include <string>
namespace llvm {
namespace lto {
/// This type defines the callback to add a pre-existing native object file
/// (e.g. in a cache).
///
/// Path is generally expected to be a valid path for the file at the point when
/// the AddBufferFn function is called, but clients should prefer to access MB
/// directly in order to avoid a potential race condition.
///
/// Buffer callbacks must be thread safe.
typedef std::function<void(unsigned Task, std::unique_ptr<MemoryBuffer> MB,
StringRef Path)>
AddBufferFn;
/// Create a local file system cache which uses the given cache directory and
/// file callback. This function also creates the cache directory if it does not
/// already exist.
Expected<NativeObjectCache> localCache(StringRef CacheDirectoryPath,
AddBufferFn AddBuffer);
} // namespace lto
} // namespace llvm
#endif