Export of internal Abseil changes

--
dea3e4f33f16bdb1d89cad1f8055b81c0c0cb554 by Andy Getzendanner <durandal@google.com>:

Validate in log_severity_test that flags of type absl::LogSeverity are lock-free.

PiperOrigin-RevId: 293454285

--
2a0cd2d8dc193a0cbff4ffa6c5c7037745507419 by Derek Mauro <dmauro@google.com>:

Update the testing instructions in CONTRIBUTING.md

PiperOrigin-RevId: 293436013

--
cec91c3f635b0b4c8a60955e5926dba4ed980898 by Gennadiy Rozental <rogeeff@google.com>:

Introduce struct to represent storage for flag value and normalize naming of internal structs in Flag implementation.

There is no semantic changes in this CL. All the internal structs are now named as Flag... We also stop using flags_internal:: qualifications for most of them since the names are unique enough by themselves.

PiperOrigin-RevId: 293251467
GitOrigin-RevId: dea3e4f33f16bdb1d89cad1f8055b81c0c0cb554
Change-Id: I161aecc9509edae3e4b77eead02df684b2ce7087

CONTRIBUTING.md

@@ -123,10 +123,13 @@ will be expected to conform to the style outlined
 
 ## Running Tests
 
-Use "bazel test <>" functionality to run the unit tests.
+If you have [Bazel](https://bazel.build/) installed, use `bazel test
+--test_tag_filters="-benchmark" ...` to run the unit tests.
 
-Prerequisites for building and running tests are listed in
-[README.md](README.md)
+If you are running the Linux operating system and have
+[Docker](https://www.docker.com/) installed, you can also run the `linux_*.sh`
+scripts under the `ci/`(https://github.com/abseil/abseil-cpp/tree/master/ci)
+directory to test Abseil under a variety of conditions.
 
 ## Abseil Committers
 

absl/base/BUILD.bazel

@@ -675,6 +675,7 @@ cc_test(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":log_severity",
+        "//absl/flags:flag_internal",
         "//absl/flags:marshalling",
         "//absl/strings",
         "@com_google_googletest//:gtest_main",

absl/base/CMakeLists.txt

@@ -610,6 +610,7 @@ absl_cc_test(
   SRCS
     "log_severity_test.cc"
   DEPS
+    absl::flags_internal
     absl::flags_marshalling
     absl::log_severity
     absl::strings

absl/base/log_severity_test.cc

@@ -24,6 +24,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include "absl/flags/internal/flag.h"
 #include "absl/flags/marshalling.h"
 #include "absl/strings/str_cat.h"
 
@@ -51,6 +52,10 @@ TEST(StreamTest, Works) {
               Eq("absl::LogSeverity(4)"));
 }
 
+static_assert(
+    absl::flags_internal::IsAtomicFlagTypeTrait<absl::LogSeverity>::value,
+    "Flags of type absl::LogSeverity ought to be lock-free.");
+
 using ParseFlagFromOutOfRangeIntegerTest = TestWithParam<int64_t>;
 INSTANTIATE_TEST_SUITE_P(
     Instantiation, ParseFlagFromOutOfRangeIntegerTest,

absl/flags/BUILD.bazel

@@ -36,7 +36,7 @@ cc_library(
     ],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = ["//visibility:private"],
+    visibility = ["//absl/base:__subpackages__"],
     deps = [
         ":config",
         ":handle",

absl/flags/flag.h

@@ -120,11 +120,11 @@ class Flag {
         return impl_;
       }
 
-      impl_ = new flags_internal::Flag<T>(
-          name_, filename_, marshalling_op_,
-          {flags_internal::FlagHelpSrc(help_gen_),
-           flags_internal::FlagHelpSrcKind::kGenFunc},
-          default_value_gen_);
+      impl_ =
+          new flags_internal::Flag<T>(name_, filename_, marshalling_op_,
+                                      {flags_internal::FlagHelpMsg(help_gen_),
+                                       flags_internal::FlagHelpKind::kGenFunc},
+                                      default_value_gen_);
       inited_.store(true, std::memory_order_release);
     }
 
@@ -152,7 +152,7 @@ class Flag {
   T Get() const { return GetImpl()->Get(); }
   bool AtomicGet(T* v) const { return GetImpl()->AtomicGet(v); }
   void Set(const T& v) { GetImpl()->Set(v); }
-  void SetCallback(const flags_internal::FlagCallback mutation_callback) {
+  void SetCallback(const flags_internal::FlagCallbackFunc mutation_callback) {
     GetImpl()->SetCallback(mutation_callback);
   }
   void InvokeCallback() { GetImpl()->InvokeCallback(); }

absl/flags/flag_test.cc

@@ -51,8 +51,8 @@ void TestCallback() {}
 
 template <typename T>
 bool TestConstructionFor() {
-  constexpr flags::HelpInitArg help_arg{flags::FlagHelpSrc("literal help"),
-                                        flags::FlagHelpSrcKind::kLiteral};
+  constexpr flags::FlagHelpArg help_arg{flags::FlagHelpMsg("literal help"),
+                                        flags::FlagHelpKind::kLiteral};
   constexpr flags::Flag<T> f1("f1", "file", &flags::FlagMarshallingOps<T>,
                               help_arg, &TestMakeDflt<T>);
   EXPECT_EQ(f1.Name(), "f1");
@@ -61,7 +61,7 @@ bool TestConstructionFor() {
 
   ABSL_CONST_INIT static flags::Flag<T> f2(
       "f2", "file", &flags::FlagMarshallingOps<T>,
-      {flags::FlagHelpSrc(&TestHelpMsg), flags::FlagHelpSrcKind::kGenFunc},
+      {flags::FlagHelpMsg(&TestHelpMsg), flags::FlagHelpKind::kGenFunc},
       &TestMakeDflt<T>);
   flags::FlagRegistrar<T, false>(&f2).OnUpdate(TestCallback);
 

absl/flags/internal/flag.cc

@@ -91,11 +91,11 @@ void FlagImpl::Init() {
 
   absl::MutexLock lock(reinterpret_cast<absl::Mutex*>(&data_guard_));
 
-  if (cur_ != nullptr) {
+  if (value_.dynamic != nullptr) {
     inited_.store(true, std::memory_order_release);
   } else {
     // Need to initialize cur field.
-    cur_ = MakeInitValue().release();
+    value_.dynamic = MakeInitValue().release();
     StoreAtomic();
     inited_.store(true, std::memory_order_release);
   }
@@ -117,15 +117,15 @@ void FlagImpl::Destroy() {
     absl::MutexLock l(DataGuard());
 
     // Values are heap allocated for Abseil Flags.
-    if (cur_) Delete(op_, cur_);
+    if (value_.dynamic) Delete(op_, value_.dynamic);
 
     // Release the dynamically allocated default value if any.
     if (def_kind_ == FlagDefaultSrcKind::kDynamicValue) {
       Delete(op_, default_src_.dynamic_value);
     }
 
     // If this flag has an assigned callback, release callback data.
-    if (callback_data_) delete callback_data_;
+    if (callback_) delete callback_;
   }
 
   absl::MutexLock l(&flag_mutex_lifetime_guard);
@@ -150,8 +150,8 @@ std::string FlagImpl::Filename() const {
 }
 
 std::string FlagImpl::Help() const {
-  return help_source_kind_ == FlagHelpSrcKind::kLiteral ? help_.literal
-                                                        : help_.gen_func();
+  return help_source_kind_ == FlagHelpKind::kLiteral ? help_.literal
+                                                     : help_.gen_func();
 }
 
 bool FlagImpl::IsModified() const {
@@ -174,27 +174,26 @@ std::string FlagImpl::DefaultValue() const {
 std::string FlagImpl::CurrentValue() const {
   absl::MutexLock l(DataGuard());
 
-  return Unparse(marshalling_op_, cur_);
+  return Unparse(marshalling_op_, value_.dynamic);
 }
 
-void FlagImpl::SetCallback(
-    const flags_internal::FlagCallback mutation_callback) {
+void FlagImpl::SetCallback(const FlagCallbackFunc mutation_callback) {
   absl::MutexLock l(DataGuard());
 
-  if (callback_data_ == nullptr) {
-    callback_data_ = new CallbackData;
+  if (callback_ == nullptr) {
+    callback_ = new FlagCallback;
   }
-  callback_data_->func = mutation_callback;
+  callback_->func = mutation_callback;
 
   InvokeCallback();
 }
 
 void FlagImpl::InvokeCallback() const {
-  if (!callback_data_) return;
+  if (!callback_) return;
 
   // Make a copy of the C-style function pointer that we are about to invoke
   // before we release the lock guarding it.
-  FlagCallback cb = callback_data_->func;
+  FlagCallbackFunc cb = callback_->func;
 
   // If the flag has a mutation callback this function invokes it. While the
   // callback is being invoked the primary flag's mutex is unlocked and it is
@@ -208,7 +207,7 @@ void FlagImpl::InvokeCallback() const {
   // completed. Requires that *primary_lock be held in exclusive mode; it may be
   // released and reacquired by the implementation.
   MutexRelock relock(DataGuard());
-  absl::MutexLock lock(&callback_data_->guard);
+  absl::MutexLock lock(&callback_->guard);
   cb();
 }
 
@@ -267,22 +266,22 @@ void FlagImpl::Read(void* dst, const flags_internal::FlagOpFn dst_op) const {
         absl::StrCat("Flag '", Name(),
                      "' is defined as one type and declared as another"));
   }
-  CopyConstruct(op_, cur_, dst);
+  CopyConstruct(op_, value_.dynamic, dst);
 }
 
 void FlagImpl::StoreAtomic() {
   size_t data_size = Sizeof(op_);
 
   if (data_size <= sizeof(int64_t)) {
     int64_t t = 0;
-    std::memcpy(&t, cur_, data_size);
-    atomics_.small_atomic.store(t, std::memory_order_release);
+    std::memcpy(&t, value_.dynamic, data_size);
+    value_.atomics.small_atomic.store(t, std::memory_order_release);
   }
 #if defined(ABSL_FLAGS_INTERNAL_ATOMIC_DOUBLE_WORD)
   else if (data_size <= sizeof(FlagsInternalTwoWordsType)) {
     FlagsInternalTwoWordsType t{0, 0};
-    std::memcpy(&t, cur_, data_size);
-    atomics_.big_atomic.store(t, std::memory_order_release);
+    std::memcpy(&t, value_.dynamic, data_size);
+    value_.atomics.big_atomic.store(t, std::memory_order_release);
   }
 #endif
 }
@@ -313,7 +312,7 @@ void FlagImpl::Write(const void* src, const flags_internal::FlagOpFn src_op) {
 
   modified_ = true;
   counter_++;
-  Copy(op_, src, cur_);
+  Copy(op_, src, value_.dynamic);
 
   StoreAtomic();
   InvokeCallback();
@@ -334,7 +333,7 @@ bool FlagImpl::SetFromString(absl::string_view value, FlagSettingMode set_mode,
   switch (set_mode) {
     case SET_FLAGS_VALUE: {
       // set or modify the flag's value
-      if (!TryParse(&cur_, value, err)) return false;
+      if (!TryParse(&value_.dynamic, value, err)) return false;
       modified_ = true;
       counter_++;
       StoreAtomic();
@@ -348,7 +347,7 @@ bool FlagImpl::SetFromString(absl::string_view value, FlagSettingMode set_mode,
     case SET_FLAG_IF_DEFAULT: {
       // set the flag's value, but only if it hasn't been set by someone else
       if (!modified_) {
-        if (!TryParse(&cur_, value, err)) return false;
+        if (!TryParse(&value_.dynamic, value, err)) return false;
         modified_ = true;
         counter_++;
         StoreAtomic();
@@ -381,7 +380,7 @@ bool FlagImpl::SetFromString(absl::string_view value, FlagSettingMode set_mode,
 
       if (!modified_) {
         // Need to set both default value *and* current, in this case
-        Copy(op_, default_src_.dynamic_value, cur_);
+        Copy(op_, default_src_.dynamic_value, value_.dynamic);
         StoreAtomic();
         InvokeCallback();
       }