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author | David Blaikie <dblaikie@gmail.com> | 2013-02-21 00:27:28 +0000 |
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committer | David Blaikie <dblaikie@gmail.com> | 2013-02-21 00:27:28 +0000 |
commit | 5c43245bf459c77077b607e1b55e6928cfbe464e (patch) | |
tree | 82fed71a9b20a0c1b252d28969f293179656996c | |
parent | 06ab2c828a5605abec36eb0d6749940fa6eb7391 (diff) | |
download | llvm-5c43245bf459c77077b607e1b55e6928cfbe464e.tar.gz llvm-5c43245bf459c77077b607e1b55e6928cfbe464e.tar.bz2 llvm-5c43245bf459c77077b607e1b55e6928cfbe464e.tar.xz |
Provide a "None" value for convenience when using Optional<T>()
This implementation of NoneType/None does have some holes but I haven't
found one that doesn't - open to improvement.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175696 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r-- | include/llvm/ADT/None.h | 27 | ||||
-rw-r--r-- | include/llvm/ADT/Optional.h | 2 | ||||
-rw-r--r-- | lib/Support/LockFileManager.cpp | 4 |
3 files changed, 31 insertions, 2 deletions
diff --git a/include/llvm/ADT/None.h b/include/llvm/ADT/None.h new file mode 100644 index 0000000000..83c952178a --- /dev/null +++ b/include/llvm/ADT/None.h @@ -0,0 +1,27 @@ +//===-- None.h - Simple null value for implicit construction ------*- C++ -*-=// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file provides None, an enumerant for use in implicit constructors +// of various (usually templated) types to make such construction more +// terse. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_ADT_NONE_H +#define LLVM_ADT_NONE_H + +namespace llvm { +/// \brief A simple null object to allow implicit construction of Optional<T> +/// and similar types without having to spell out the specialization's name. +enum NoneType { + None +}; +} + +#endif diff --git a/include/llvm/ADT/Optional.h b/include/llvm/ADT/Optional.h index 6c91a13a5b..b0d09f6960 100644 --- a/include/llvm/ADT/Optional.h +++ b/include/llvm/ADT/Optional.h @@ -16,6 +16,7 @@ #ifndef LLVM_ADT_OPTIONAL_H #define LLVM_ADT_OPTIONAL_H +#include "llvm/ADT/None.h" #include "llvm/Support/Compiler.h" #include "llvm/Support/AlignOf.h" #include <cassert> @@ -31,6 +32,7 @@ class Optional { AlignedCharArrayUnion<T> storage; bool hasVal; public: + Optional(NoneType) : hasVal(false) {} explicit Optional() : hasVal(false) {} Optional(const T &y) : hasVal(true) { new (storage.buffer) T(y); diff --git a/lib/Support/LockFileManager.cpp b/lib/Support/LockFileManager.cpp index 31eec751b7..92d8b83cf9 100644 --- a/lib/Support/LockFileManager.cpp +++ b/lib/Support/LockFileManager.cpp @@ -31,7 +31,7 @@ LockFileManager::readLockFile(StringRef LockFileName) { // to read, so we just return. bool Exists = false; if (sys::fs::exists(LockFileName, Exists) || !Exists) - return Optional<std::pair<std::string, int> >(); + return None; // Read the owning host and PID out of the lock file. If it appears that the // owning process is dead, the lock file is invalid. @@ -45,7 +45,7 @@ LockFileManager::readLockFile(StringRef LockFileName) { // Delete the lock file. It's invalid anyway. bool Existed; sys::fs::remove(LockFileName, Existed); - return Optional<std::pair<std::string, int> >(); + return None; } bool LockFileManager::processStillExecuting(StringRef Hostname, int PID) { |