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Export of internal Abseil changes

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90ecacd2a3db96ee64ef23af37a80fad404e2b32 by Gennadiy Rozental <rogeeff@google.com>:

Fixes MSVC regression by making MSVC version of class Flag into an aggregate type.

PiperOrigin-RevId: 277767054

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018f3b040df51d91a988fa146fee163721e605e9 by Abseil Team <absl-team@google.com>:

Change libstdc++ lacking std::unique_ptr check from a gcc version check to based on feature macros.

PiperOrigin-RevId: 277736042

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475844775ae343e2414318f08549ee3fa6676a8d by CJ Johnson <johnsoncj@google.com>:

Pass allocator_type through allocator_traits before extracting the typedefs

PiperOrigin-RevId: 277730393

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d843bc4bc30bf5b11af76db8beda8634b6111a62 by Abseil Team <absl-team@google.com>:

Convert the Waiter::Init() method to the default constructor and define
a destructor for the Waiter class.

Use placement new and delete with Waiter objects.

PiperOrigin-RevId: 277728823

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1ba6edf421dd2dfe13c55970a03c99592cb6677d by Derek Mauro <dmauro@google.com>:

Use lowercase spelling for include of dbghelp.h
When cross-compiling under MinGW this is important

PiperOrigin-RevId: 277629783

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cfc662a6fa357a84ddda8037156c7f26cee40c36 by Abseil Team <absl-team@google.com>:

Don't use atomic ops on waiter and wakeup counts in WIN32 waiter mode.

Port the new CONDVAR waiter mode code in CL 277366017 to the WIN32
waiter mode.

PiperOrigin-RevId: 277603611

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833106542e61fa0832900adf3c1b2afc6890b94b by Abseil Team <absl-team@google.com>:

Add the PerThreadSem::Destroy() method.

For ABSL_WAITER_MODE_CONDVAR or ABSL_WAITER_MODE_SEM,
PerThreadSem::Destroy() is used to destroy the pthread mutex and
condition variable or the POSIX semaphore.
PiperOrigin-RevId: 277586675

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7814da4a59106cf1e0e4db1a31b9592ebbd2094b by Samuel Benzaquen <sbenza@google.com>:

Enable the assertion in the iterator's operator* and operator->

PiperOrigin-RevId: 277563401
GitOrigin-RevId: 90ecacd2a3db96ee64ef23af37a80fad404e2b32
Change-Id: Ib19be3680da74f0b94055c9039115ec6bcaea7b0
This commit is contained in:
Abseil Team 2019-10-31 11:37:35 -07:00 • committed by vslashg
parent 83880e3d8c
commit 846e5dbeda
13 changed files with 238 additions and 143 deletions
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70
absl/flags/flag.h
View file

@ -67,17 +67,20 @@ namespace absl {
template <typename T>
using Flag = flags_internal::Flag<T>;
#else
// MSVC debug builds do not implement constexpr correctly for classes with
// virtual methods. To work around this we adding level of indirection, so that
// the class `absl::Flag` contains an `internal::Flag*` (instead of being an
// alias to that class) and dynamically allocates an instance when necessary.
// We also forward all calls to internal::Flag methods via trampoline methods.
// In this setup the `absl::Flag` class does not have virtual methods and thus
// MSVC is able to initialize it at link time. To deal with multiple threads
// accessing the flag for the first time concurrently we use an atomic boolean
// indicating if flag object is constructed. We also employ the double-checked
// locking pattern where the second level of protection is a global Mutex, so
// if two threads attempt to construct the flag concurrently only one wins.
// MSVC debug builds do not implement initialization with constexpr constructors
// correctly. To work around this we add a level of indirection, so that the
// class `absl::Flag` contains an `internal::Flag*` (instead of being an alias
// to that class) and dynamically allocates an instance when necessary. We also
// forward all calls to internal::Flag methods via trampoline methods. In this
// setup the `absl::Flag` class does not have constructor and virtual methods,
// all the data members are public and thus MSVC is able to initialize it at
// link time. To deal with multiple threads accessing the flag for the first
// time concurrently we use an atomic boolean indicating if flag object is
// initialized. We also employ the double-checked locking pattern where the
// second level of protection is a global Mutex, so if two threads attempt to
// construct the flag concurrently only one wins.
// This solution is based on a recomendation here:
// https://developercommunity.visualstudio.com/content/problem/336946/class-with-constexpr-constructor-not-using-static.html?childToView=648454#comment-648454
namespace flags_internal {
absl::Mutex* GetGlobalConstructionGuard();
@ -86,16 +89,23 @@ absl::Mutex* GetGlobalConstructionGuard();
template <typename T>
class Flag {
public:
// No constructor and destructor to ensure this is an aggregate type.
// Visual Studio 2015 still requires the constructor for class to be
// constexpr initializable.
#if _MSC_VER <= 1900
constexpr Flag(const char* name, const flags_internal::HelpGenFunc help_gen,
const char* filename,
const flags_internal::FlagMarshallingOpFn marshalling_op,
const flags_internal::InitialValGenFunc initial_value_gen)
const flags_internal::InitialValGenFunc initial_value_gen,
bool, void*)
: name_(name),
help_gen_(help_gen),
filename_(filename),
marshalling_op_(marshalling_op),
initial_value_gen_(initial_value_gen),
inited_(false) {}
inited_(false),
impl_(nullptr) {}
#endif
flags_internal::Flag<T>* GetImpl() const {
if (!inited_.load(std::memory_order_acquire)) {
@ -113,7 +123,8 @@ class Flag {
return impl_;
}
// absl::Flag API
// Public methods of `absl::Flag<T>` are NOT part of the Abseil Flags API.
// See https://abseil.io/docs/cpp/guides/flags
bool IsRetired() const { return GetImpl()->IsRetired(); }
bool IsAbseilFlag() const { return GetImpl()->IsAbseilFlag(); }
absl::string_view Name() const { return GetImpl()->Name(); }
@ -126,9 +137,9 @@ class Flag {
std::string Filename() const { return GetImpl()->Filename(); }
std::string DefaultValue() const { return GetImpl()->DefaultValue(); }
std::string CurrentValue() const { return GetImpl()->CurrentValue(); }
template <typename T1>
template <typename U>
inline bool IsOfType() const {
return GetImpl()->template IsOfType<T1>();
return GetImpl()->template IsOfType<U>();
}
T Get() const { return GetImpl()->Get(); }
bool AtomicGet(T* v) const { return GetImpl()->AtomicGet(v); }
@ -138,7 +149,8 @@ class Flag {
}
void InvokeCallback() { GetImpl()->InvokeCallback(); }
private:
// The data members are logically private, but they need to be public for
// this to be an aggregate type.
const char* name_;
const flags_internal::HelpGenFunc help_gen_;
const char* filename_;
@ -146,7 +158,7 @@ class Flag {
const flags_internal::InitialValGenFunc initial_value_gen_;
mutable std::atomic<bool> inited_;
mutable flags_internal::Flag<T>* impl_ = nullptr;
mutable flags_internal::Flag<T>* impl_;
};
#endif
@ -310,17 +322,35 @@ void SetFlag(absl::Flag<T>* flag, const V& v) {
// Note: Name of registrar object is not arbitrary. It is used to "grab"
// global name for FLAGS_no<flag_name> symbol, thus preventing the possibility
// of defining two flags with names foo and nofoo.
#if !defined(_MSC_VER) || defined(__clang__)
#define ABSL_FLAG_IMPL(Type, name, default_value, help) \
namespace absl /* block flags in namespaces */ {} \
ABSL_FLAG_IMPL_DECLARE_DEF_VAL_WRAPPER(name, Type, default_value) \
ABSL_FLAG_IMPL_DECLARE_HELP_WRAPPER(name, help) \
ABSL_CONST_INIT absl::Flag<Type> FLAGS_##name( \
ABSL_CONST_INIT absl::Flag<Type> FLAGS_##name{ \
ABSL_FLAG_IMPL_FLAGNAME(#name), &AbslFlagsWrapHelp##name, \
ABSL_FLAG_IMPL_FILENAME(), \
&absl::flags_internal::FlagMarshallingOps<Type>, \
&AbslFlagsInitFlag##name); \
&AbslFlagsInitFlag##name}; \
extern bool FLAGS_no##name; \
bool FLAGS_no##name = ABSL_FLAG_IMPL_REGISTRAR(Type, FLAGS_##name)
#else
// MSVC version uses aggregate initialization.
#define ABSL_FLAG_IMPL(Type, name, default_value, help) \
namespace absl /* block flags in namespaces */ {} \
ABSL_FLAG_IMPL_DECLARE_DEF_VAL_WRAPPER(name, Type, default_value) \
ABSL_FLAG_IMPL_DECLARE_HELP_WRAPPER(name, help) \
ABSL_CONST_INIT absl::Flag<Type> FLAGS_##name{ \
ABSL_FLAG_IMPL_FLAGNAME(#name), \
&AbslFlagsWrapHelp##name, \
ABSL_FLAG_IMPL_FILENAME(), \
&absl::flags_internal::FlagMarshallingOps<Type>, \
&AbslFlagsInitFlag##name, \
false, \
nullptr}; \
extern bool FLAGS_no##name; \
bool FLAGS_no##name = ABSL_FLAG_IMPL_REGISTRAR(Type, FLAGS_##name)
#endif
// ABSL_RETIRED_FLAG
//