Changes imported from Abseil "staging" branch:

  - 06c8c67f5a564d00696e023060f05a5c34e7e164 IWYU | absl/base by Juemin Yang <jueminyang@google.com>
  - 2b1a054a09bda55843b449843b2a125741e936e7 Internal refactoring by Greg Miller <jgm@google.com>
  - f43f7f1f91bee26b5ddcd0c5bbbc47cb977aef77 Make std::hash<absl::optional<T>> to be standard compliant: by Xiaoyi Zhang <zhangxy@google.com>
  - 539bad2ebc22e610e1f292285a30a87945bc663e Update utility.h to Abseil standards by Tom Manshreck <shreck@google.com>
  - d05ec10a5f16a5d6640e0db91ecc7ab3ea971fd4 Add a test for absl::Barrier. by Derek Mauro <dmauro@google.com>
  - d707e27acb3c06f0d74c5f7ad7861e3841a5471f Run leak-checking tool over all outbound code. by Daniel Katz <katzdm@google.com>
  - 55f07f482a50422b8f99f7176374a19d0d473c5f Add alignas(16) to uint128. by Alex Strelnikov <strel@google.com>
  - 94999b7edde82308f736fb939501537ee9edbca6 Update attributes.h to Abseil standards by Tom Manshreck <shreck@google.com>
  - 321bed0061c41b53d0206ad4865528c00dd6d825 Test git merge + piper cl process by Juemin Yang <jueminyang@google.com>
  - 69920e7351a1053a7f4940bbde1768e839ce84bc Adds support for "/etc/localtime" as an embedded time zon... by Greg Miller <jgm@google.com>
  - 6839c06bf232903d3a9cbffa6eb2c960db78e67b Add copyright notices to inlined_vector code. by Greg Falcon <gfalcon@google.com>
  - 4e2714f6266263515cdfd31675c30c6ed6f98e1a Adding Apache 2.0 License by Gennadiy Civil <misterg@google.com>
  - 7402e7594016a4cd0a8b823fe6bc1bad1874bb85 IWYU | absl/utility by Juemin Yang <jueminyang@google.com>
  - 271a3812337eed97c412042738482688a80e19bd IWYU | absl/memory by Juemin Yang <jueminyang@google.com>
  - 32bda13a8098c2b06e25a5cf7bb782d6b79eb006 IWYU | absl/numeric by Juemin Yang <jueminyang@google.com>
  - 62d375cedc133108904bc06e340e303091a565df Remove "no_test"-annotations on span_test_noexceptions. by Daniel Katz <katzdm@google.com>
  - ebcbae9a55a93a7f1bb6862edc2715a6d9877206 Move CI-testing support files out of public-facing reposi... by Daniel Katz <katzdm@google.com>
  - d3f05eff4daa6030bfacb31cca0f9213fb702247 Fixes ToInt64Minutes() and ToInt64Hours() to properly sat... by Greg Miller <jgm@google.com>
  - b8dfae3facb6bb002622f083a10d14448f19e6e0 Fix typo. by Abseil Team <absl-team@google.com>
  - 150f03baa0afa231c2fc01597ea2321da586caba Update README.md by Yilei Yang <yileiyang@google.com>
  - 05276aa837dd081686518fd27bda4bd206ac4443 Adding Apache 2.0 License by Gennadiy Civil <misterg@google.com>
  - 37bf8e223e79ad06a195e28db9499e0c3d140f73 IWYU | absl/container by Juemin Yang <jueminyang@google.com>
  - 49164928f220978a32f88d16a55549bdf871daef IWYU | absl/algorithm by Juemin Yang <jueminyang@google.com>
  - a6804734e129039f9580a4fcd0f66425d0d0ac30 Move throw delegate wrappers to an internal namespace. by Greg Falcon <gfalcon@google.com>
  - ac83e73f67f593e2aff957b2be0b28e59c552a71 Fix error in comment stripping directives. by Greg Falcon <gfalcon@google.com>
  - e018a24185a984e787fb81a75fc35b74ad3a4d3d Update copyright headers all BUILD files by Gennadiy Civil <misterg@google.com>
  - a3be0990bfd76b0dec76bd85cecfa4dcec68b3ea Fix closing namespace comment typo. by Abseil Team <absl-team@google.com>
  - be3e3c4327e4f83949e0f29fd7a190d7eaa8b50b Update TODO by Abseil Team <absl-team@google.com>
  - f56a5d6f72685d92bb9c2905841b950d8177210c Add test-coverage for leak-sanitizer. by Daniel Katz <katzdm@google.com>
  - 7694bf161c7e00fdd08bfadc2aaf8e0fb09335f8 span.h: further touch up wording around the std::initiali... by Abseil Team <absl-team@google.com>
  - 3a12e081c0f8b359973e020d1e91f65356548ebc Update time.h to Abseil standards by Tom Manshreck <shreck@google.com>
  - 48d28f6468129420f4b20d451dca8e08012a7a77 Remove references to google from comments in Abseil. by Greg Falcon <gfalcon@google.com>
  - 773e34402d15fcad6370d5ed2430482d17db910d Rename the ExpectTime macro to match Abseil naming conven... by Greg Falcon <gfalcon@google.com>
  - 774d2ff1fe26c7313b301ff203e83e1aaac86627 Internal change. by Daniel Katz <katzdm@google.com>
  - 2e8a5830e95c8a1b839721bb2f1d4f5c85b9fb60 Fix typo in comment (missing '*' on a pointer). by Abseil Team <absl-team@google.com>
  - 458106feb707cf9609dd243713bde44aa9679e2a Correct capitalization: github -> GitHub by Yilei Yang <yileiyang@google.com>
  - af440725f02c2a83ca5cbaf176e1142f9e9d9b2f Update copyright headers by Gennadiy Civil <misterg@google.com>
  - 05b1118cce4ab87d23c33d48e64a96bcfec08761 Update copyright headers by Gennadiy Civil <misterg@google.com>
  - d5c6669a62d047156bb77055c5da03ee1b3c61b9 Update Abseil README to include descriptions of the inclu... by Tom Manshreck <shreck@google.com>
  - 3cd7e4663dddc840087469a6495f6cf433bfad8d Update copyright headers in //base by Tom Manshreck <shreck@google.com>
  - 7a876da657cd6698c5da2008a582d52eedc85dd1 Update strings overview with robust string library docume... by Tom Manshreck <shreck@google.com>
  - d9e3d0768d6f1c77d30992bdbef7b47ec92994bb Update copyright headers all BUILD files by Abseil Team <absl-team@google.com>
  - 6fe942728bceb0625f7c79b2840c4a6154d076b3 Make InlinedVector, FixedArray, and Span's at() throw on ... by Jon Cohen <cohenjon@google.com>
  - 5b52d5ec6cb9fbb07fc2e2fa020bd3eeb48c4953 Update clock.h to Abseil standards by Tom Manshreck <shreck@google.com>
  - c03c1ca3aee8bb7e40aa0315f6c432d31a72c30c Update //algorithm copyright headers by Tom Manshreck <shreck@google.com>
  - d46f40ddc596aaacb0459351d0e4aa6871289fa2 Temporarily prevent running mutex_test on crosstool17, wh... by Jon Cohen <cohenjon@google.com>
  - 61f11476189df68edfb9908308d677a91f03ff67 Update copyright headers in //container by Tom Manshreck <shreck@google.com>
  - 91832c00948954edf0b3dda12219c9a0202421ac Update copyright headers for //synchronization by Tom Manshreck <shreck@google.com>
  - 4e09100264b4585af6b4508ff35b9c627ac1f1ce Update copyright headers all BUILD files by Gennadiy Civil <misterg@google.com>
  - 13a0e8aebedec0f95b33750cbcd6b5548619b2a5 Update copyright headers in //memory by Tom Manshreck <shreck@google.com>
  - 63e1b9d4fdbcdf097e5276050ad1f76f0053e553 Update copyright headers for //strings (+ one from //nume... by Tom Manshreck <shreck@google.com>
  - 0108e7cfc50777a94c56d00e9c305161364df341 Convert ASSERT and EXPECT to ABSL_RAW_CHECK in helper fun... by Derek Mauro <dmauro@google.com>
  - 0122306fe47a3093248254a1b475c3a1d82abec5 Internal change by Abseil Team <absl-team@google.com>
  - 89c0c2698c98a12cd63172eeb02063b2f67e7c81 #absl Fix comment. by Abseil Team <absl-team@google.com>
  - 6621cc1ff54800e0aadb5e3071dbaa84b2077ceb Publishing contributing guidelines. by Gennadiy Civil <misterg@google.com>
  - e48c5be3c75e794b3e3827d40915b01fe1a1afc5 Avoid PRIdPTR.  Cast to long long and use %lld insted. by Abseil Team <absl-team@google.com>
  - 2640ea4a260d89b94b07a3142660327e47db33fd No algorithmic changes. by Abseil Team <absl-team@google.com>
  - 1bc6c1bad17754f5d84963bf1d0db279402a0a1d Internal change. by Derek Mauro <dmauro@google.com>
  - 6845d24733e8c95bebde825ba78a2abfd9e35bdb span.h: fix up incorrect wording around lvalues. by Abseil Team <absl-team@google.com>
  - d8f5caee721e252e5f9b1080fb996363f498ac28 Add more exaustive Mutex testing. by Derek Mauro <dmauro@google.com>
  - e8b4cb053eb98858eef10cc53280b6ed5d6815a7 Change Span::subspan to not call into a deprecated constr... by Jon Cohen <cohenjon@google.com>
  - 49c36a82b3114926390557670aaaf0ea25b5760c s/std::size_t/size_t/g by Jon Cohen <cohenjon@google.com>
  - e17487c3c4d4a99f2fd8bc3e42176fc3171614d1 Account for the case of timeval::tv_sec being smaller than by Abseil Team <absl-team@google.com>
  - ecbb89d5fb98483e777c03d97ac02d7b7b54985e Alias absl::string_view to std::string_view when C++17 st... by Xiaoyi Zhang <zhangxy@google.com>
  - 6820e5a51459cdbb6a423cbae25a0cc839c85d44 Internal cleanup. by Xiaoyi Zhang <zhangxy@google.com>
  - 6976469b76a6faaf4111a24ddb37f40211ffadae More Span constexpr by Jon Cohen <cohenjon@google.com>
  - 8521c8956eee1125b7759eb272ec4a5a86fcefc5 #absl Fix comment. by Abseil Team <absl-team@google.com>
  - 20eae7a67fde5dd809aa47e5f7de8a493701645e Embed enough zoneinfo data to make time:time_test (under ... by Abseil Team <absl-team@google.com>
  - 841f5d98ceef4a423839ea73ee06c2f47a9b9680 Clean up macros in attributes.h | ATTRIBUTE_INITIAL_EXEC by Juemin Yang <jueminyang@google.com>
  - 83d8b36656e47919b5d0bac82eece897e195697e Update any.h comments to Abseil standards by Tom Manshreck <shreck@google.com>
  - bb3fae11d3459eeae2f63bfd22e65d3193187cc8 Update type_traits.h comments to Abseil standards by Tom Manshreck <shreck@google.com>
  - 992e1b07c0dec64271f8c44f22fd8df3734d0c47 Renamespace CycleClock code. by Greg Falcon <gfalcon@google.com>
  - 08d6fb0594098493ffbc0e737405182638122e7e Eliminate more existing lint warnings by Gennadiy Rozental <rogeeff@google.com>
  - 1cc6fdc71eb777497239f8c3e9168e6c9d40ea53 Update optional.h to Abseil standards by Tom Manshreck <shreck@google.com>
  - baa91747aa55009a9eb31b6072e33db06cfce2d2 Enforce internal namespace symbol reference policy by Gennadiy Rozental <rogeeff@google.com>
  - 939251e39342ce559e5d23fe43799671581f7cf5 Add CycleClock scaling shift to mitigate a possible overf... by Derek Mauro <dmauro@google.com>
  - c6dfdeecea0c7470938bed47c99ea2b2a95889d8 Add constexpr tests for absl::make_optional(). by Xiaoyi Zhang <zhangxy@google.com>
  - 509e949b992db33041d840746fbd05cc01cb206e Alias absl::optional to std::optional when C++17 std::opt... by Xiaoyi Zhang <zhangxy@google.com>
  - a1ae6d96a8826ba75281cac8632a766b5856acaf Remove no_test_* tags from span_test to increase test cov... by Xiaoyi Zhang <zhangxy@google.com>
  - 3c2a43cc09791723c8a324836629644ac44cb9c8 Remove accidental bits of Google-internal code and short ... by Greg Falcon <gfalcon@google.com>
  - 4874d49d496ac0b6ec36f4280a14b2159e7af930 Replaces the macro-generated Duration factory functions e... by Greg Miller <jgm@google.com>
  - 90e62695e03cb4a57e137ca0c3e116b1d802db57 Fix namespacing for a couple files in base/internal, and ... by Greg Falcon <gfalcon@google.com>
  - b0e6e00e34f967924849aaf8c123bba068f093e3 Publishing contributing guidelines. by Gennadiy Civil <misterg@google.com>
  - d74eafbccc3dffa6c25f9b6a2219425a24b5a959 Internal change by Abseil Team <absl-team@google.com>
  - 27477badbbf720265f5b9509b6c0e01913dc0a9f Update escaping.h comments to Abseil standards by Tom Manshreck <shreck@google.com>
  - 67002f55738319c2875197c3b6282de215ec250d adds absl namespace to debugging/stacktrace.h by Behzad Nouri <bnouri@google.com>
  - e608018f7faa384d5b202ac0a4c7a0d5166f4d9c Update string_view.h comments to Abseil standards by Tom Manshreck <shreck@google.com>
  - e884f04d4c648e01ed7dcde2fda80c24e8452047 Exclude strings/ files we are not releasing from OSS univ... by Gennadiy Rozental <rogeeff@google.com>
  - 3f4c4032ed520f2dd10a81d58ef4f399c001c5cc Strip out eventmanager reference from release. by Gennadiy Rozental <rogeeff@google.com>
  - fb0f1c204793c3792bad101dbaa734e7c2a35887 Fix copybara strip comments by Gennadiy Rozental <rogeeff@google.com>
  - 3eaaac942f77c3d41d63d414630403bfd0f6b70c Strip out style guide waivers. by Gennadiy Rozental <rogeeff@google.com>
  - 020e045058173178b51266b99a2a5dc9ed921960 substitute_test portability | MUST_USE_RESULT cast-to-voi... by Juemin Yang <jueminyang@google.com>
  - 86c093bf81d80ff537ed5e8b89225ce75a636220 Internal change. by Derek Mauro <dmauro@google.com>
  - 330375eb952fe78276e75631a28e750d5bfdb198 Prefer absl::FixedTimeZone() over loading "Etc/GMT[-+]<N>". by Abseil Team <absl-team@google.com>
  - 2e07ebee46a8201adc0dfd2c4ddb3df76e524357 Internal change. by Derek Mauro <dmauro@google.com>
  - 1f0c8b78c8ebd66f14cdf39fcba9f4c9986dcdca ::absl -> absl by Gennadiy Rozental <rogeeff@google.com>
  - ad163566d12ea08f1da2c23931eeacfffc564139 Avoid old style loops where possible. by Gennadiy Rozental <rogeeff@google.com>
  - bce2108818fe57b5617ce0090ddd4f753808f0a1 Update comments in str_cat.h in line with recent changes. by Abseil Team <absl-team@google.com>
  - cfd593a80f4897256f2ce1ea0be55dc14e3fcad4 Copybara-out gtl aliases. by Gennadiy Rozental <rogeeff@google.com>
  - 584f1524d717993c1a16093caccd9ed2b1e5409e Fix a warning for Windows/Kokoro time_test.cc. by Daniel Katz <katzdm@google.com>
  (And 562 more changes)

GitOrigin-RevId: 06c8c67f5a564d00696e023060f05a5c34e7e164
Change-Id: I89907a6188fe7de05da400bf49ddfeba242aff8e

1 files changed, 146 insertions, 80 deletions

diff --git a/absl/base/attributes.h b/absl/base/attributes.h
index 5eecdabedb16..c2155a4e213d 100644
--- a/absl/base/attributes.h
+++ b/absl/base/attributes.h
@@ -12,39 +12,61 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
-// Various macros for C++ attributes
+// This header file defines macros for declaring attributes for functions,
+// types, and variables.
+//
+// These macros are used within Abseil and allow the compiler to optimize, where
+// applicable, certain function calls.
+//
 // This file is used for both C and C++!
 //
 // Most macros here are exposing GCC or Clang features, and are stubbed out for
 // other compilers.
+//
 // GCC attributes documentation:
-// https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Function-Attributes.html
-// https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Variable-Attributes.html
-// https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Type-Attributes.html
-//
-// Most attributes in this file are already supported by GCC 4.7.
-// However, some of them are not supported in older version of Clang.
-// Thus, we check __has_attribute() first. If the check fails, we check if we
-// are on GCC and assume the attribute exists on GCC (which is verified on GCC
-// 4.7).
-//
-// For sanitizer-related attributes, define the following macros
-// using -D along with the given value for -fsanitize:
-// - ADDRESS_SANITIZER with -fsanitize=address (GCC 4.8+, Clang)
-// - MEMORY_SANITIZER with -fsanitize=memory (Clang)
-// - THREAD_SANITIZER with -fsanitize=thread (GCC 4.8+, Clang)
-// - UNDEFINED_BEHAVIOR_SANITIZER with -fsanitize=undefined (GCC 4.9+, Clang)
-// - CONTROL_FLOW_INTEGRITY with -fsanitize=cfi (Clang)
-// Since these are only supported by GCC and Clang now, we only check for
-// __GNUC__ (GCC or Clang) and the above macros.
+//   https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Function-Attributes.html
+//   https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Variable-Attributes.html
+//   https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Type-Attributes.html
+//
+// Most attributes in this file are already supported by GCC 4.7. However, some
+// of them are not supported in older version of Clang. Thus, we check
+// `__has_attribute()` first. If the check fails, we check if we are on GCC and
+// assume the attribute exists on GCC (which is verified on GCC 4.7).
+//
+// -----------------------------------------------------------------------------
+// Sanitizer Attributes
+// -----------------------------------------------------------------------------
+//
+// Sanitizer-related attributes are not "defined" in this file (and indeed
+// are not defined as such in any file). To utilize the following
+// sanitizer-related attributes within your builds, define the following macros
+// within your build using a `-D` flag, along with the given value for
+// `-fsanitize`:
+//
+//   * `ADDRESS_SANITIZER` + `-fsanitize=address` (Clang, GCC 4.8)
+//   * `MEMORY_SANITIZER` + `-fsanitize=memory` (Clang-only)
+//   * `THREAD_SANITIZER + `-fsanitize=thread` (Clang, GCC 4.8+)
+//   * `UNDEFINED_BEHAVIOR_SANITIZER` + `-fsanitize=undefined` (Clang, GCC 4.9+)
+//   * `CONTROL_FLOW_INTEGRITY` + -fsanitize=cfi (Clang-only)
+//
+// Example:
+//
+//   // Enable branches in the Abseil code that are tagged for ASan:
+//   $ bazel -D ADDRESS_SANITIZER -fsanitize=address *target*
+//
+// Since these macro names are only supported by GCC and Clang, we only check
+// for `__GNUC__` (GCC or Clang) and the above macros.
 #ifndef ABSL_BASE_ATTRIBUTES_H_
 #define ABSL_BASE_ATTRIBUTES_H_
 
-// ABSL_HAVE_ATTRIBUTE is a function-like feature checking macro.
-// It's a wrapper around __has_attribute, which is defined by GCC 5+ and Clang.
-// It evaluates to a nonzero constant integer if the attribute is supported
-// or 0 if not.
-// It evaluates to zero if __has_attribute is not defined by the compiler.
+// ABSL_HAVE_ATTRIBUTE
+//
+// A function-like feature checking macro that is a wrapper around
+// `__has_attribute`, which is defined by GCC 5+ and Clang and evaluates to a
+// nonzero constant integer if the attribute is supported or 0 if not.
+//
+// It evaluates to zero if `__has_attribute` is not defined by the compiler.
+//
 // GCC: https://gcc.gnu.org/gcc-5/changes.html
 // Clang: https://clang.llvm.org/docs/LanguageExtensions.html
 #ifdef __has_attribute
@@ -53,11 +75,12 @@
 #define ABSL_HAVE_ATTRIBUTE(x) 0
 #endif
 
-// ABSL_HAVE_CPP_ATTRIBUTE is a function-like feature checking macro that
-// accepts C++11 style attributes. It's a wrapper around __has_cpp_attribute,
-// defined by ISO C++ SD-6
+// ABSL_HAVE_CPP_ATTRIBUTE
+//
+// A function-like feature checking macro that accepts C++11 style attributes.
+// It's a wrapper around `__has_cpp_attribute`, defined by ISO C++ SD-6
 // (http://en.cppreference.com/w/cpp/experimental/feature_test). If we don't
-// find __has_cpp_attribute, will evaluate to 0.
+// find `__has_cpp_attribute`, will evaluate to 0.
 #if defined(__cplusplus) && defined(__has_cpp_attribute)
 // NOTE: requiring __cplusplus above should not be necessary, but
 // works around https://bugs.llvm.org/show_bug.cgi?id=23435.
@@ -69,15 +92,18 @@
 // -----------------------------------------------------------------------------
 // Function Attributes
 // -----------------------------------------------------------------------------
+//
 // GCC: https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
 // Clang: https://clang.llvm.org/docs/AttributeReference.html
 
-// ABSL_PRINTF_ATTRIBUTE, ABSL_SCANF_ATTRIBUTE
-// Tell the compiler to do printf format std::string checking if the
+// ABSL_PRINTF_ATTRIBUTE
+// ABSL_SCANF_ATTRIBUTE
+//
+// Tells the compiler to perform `printf` format std::string checking if the
 // compiler supports it; see the 'format' attribute in
 // <http://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Function-Attributes.html>.
 //
-// N.B.: As the GCC manual states, "[s]ince non-static C++ methods
+// Note: As the GCC manual states, "[s]ince non-static C++ methods
 // have an implicit 'this' argument, the arguments of such methods
 // should be counted from two, not one."
 #if ABSL_HAVE_ATTRIBUTE(format) || (defined(__GNUC__) && !defined(__clang__))
@@ -90,9 +116,10 @@
 #define ABSL_SCANF_ATTRIBUTE(string_index, first_to_check)
 #endif
 
-// ABSL_ATTRIBUTE_ALWAYS_INLINE, ABSL_ATTRIBUTE_NOINLINE
-// For functions we want to force inline or not inline.
-// Introduced in gcc 3.1.
+// ABSL_ATTRIBUTE_ALWAYS_INLINE
+// ABSL_ATTRIBUTE_NOINLINE
+//
+// Forces functions to either inline or not inline. Introduced in gcc 3.1.
 #if ABSL_HAVE_ATTRIBUTE(always_inline) || \
     (defined(__GNUC__) && !defined(__clang__))
 #define ABSL_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
@@ -109,7 +136,8 @@
 #endif
 
 // ABSL_ATTRIBUTE_NO_TAIL_CALL
-// Prevent the compiler from optimizing away stack frames for functions which
+//
+// Prevents the compiler from optimizing away stack frames for functions which
 // end in a call to another function.
 #if ABSL_HAVE_ATTRIBUTE(disable_tail_calls)
 #define ABSL_HAVE_ATTRIBUTE_NO_TAIL_CALL 1
@@ -122,8 +150,10 @@
 #define ABSL_ATTRIBUTE_NO_TAIL_CALL
 #define ABSL_HAVE_ATTRIBUTE_NO_TAIL_CALL 0
 #endif
+
 // ABSL_ATTRIBUTE_WEAK
-// For weak functions
+//
+// Tags a function as weak for the purposes of compilation and linking.
 #if ABSL_HAVE_ATTRIBUTE(weak) || (defined(__GNUC__) && !defined(__clang__))
 #undef ABSL_ATTRIBUTE_WEAK
 #define ABSL_ATTRIBUTE_WEAK __attribute__((weak))
@@ -132,9 +162,11 @@
 #define ABSL_ATTRIBUTE_WEAK
 #define ABSL_HAVE_ATTRIBUTE_WEAK 0
 #endif
+
 // ABSL_ATTRIBUTE_NONNULL
-// Tell the compiler either that a particular function parameter
-// should be a non-null pointer, or that all pointer arguments should
+//
+// Tells the compiler either (a) that a particular function parameter
+// should be a non-null pointer, or (b) that all pointer arguments should
 // be non-null.
 //
 // Note: As the GCC manual states, "[s]ince non-static C++ methods
@@ -142,10 +174,13 @@
 // should be counted from two, not one."
 //
 // Args are indexed starting at 1.
-// For non-static class member functions, the implicit "this" argument
-// is arg 1, and the first explicit argument is arg 2.
-// For static class member functions, there is no implicit "this", and
-// the first explicit argument is arg 1.
+//
+// For non-static class member functions, the implicit `this` argument
+// is arg 1, and the first explicit argument is arg 2. For static class member
+// functions, there is no implicit `this`, and the first explicit argument is
+// arg 1.
+//
+// Example:
 //
 //   /* arg_a cannot be null, but arg_b can */
 //   void Function(void* arg_a, void* arg_b) ABSL_ATTRIBUTE_NONNULL(1);
@@ -171,8 +206,10 @@
 #else
 #define ABSL_ATTRIBUTE_NONNULL(...)
 #endif
+
 // ABSL_ATTRIBUTE_NORETURN
-// Tell the compiler that a given function never returns
+//
+// Tells the compiler that a given function never returns.
 #if ABSL_HAVE_ATTRIBUTE(noreturn) || (defined(__GNUC__) && !defined(__clang__))
 #define ABSL_ATTRIBUTE_NORETURN __attribute__((noreturn))
 #elif defined(_MSC_VER)
@@ -180,8 +217,10 @@
 #else
 #define ABSL_ATTRIBUTE_NORETURN
 #endif
+
 // ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS
-// Tell AddressSanitizer (or other memory testing tools) to ignore a given
+//
+// Tells the AddressSanitizer (or other memory testing tools) to ignore a given
 // function. Useful for cases when a function reads random locations on stack,
 // calls _exit from a cloned subprocess, deliberately accesses buffer
 // out of bounds or does other scary things with memory.
@@ -194,11 +233,12 @@
 #endif
 
 // ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY
-// Tell MemorySanitizer to relax the handling of a given function. All "Use of
-// uninitialized value" warnings from such functions will be suppressed, and all
-// values loaded from memory will be considered fully initialized.
-// This is similar to the ADDRESS_SANITIZER attribute above, but deals with
-// initializedness rather than addressability issues.
+//
+// Tells the  MemorySanitizer to relax the handling of a given function. All
+// "Use of uninitialized value" warnings from such functions will be suppressed,
+// and all values loaded from memory will be considered fully initialized.
+// This attribute is similar to the ADDRESS_SANITIZER attribute above, but deals
+// with initialized-ness rather than addressability issues.
 // NOTE: MemorySanitizer(msan) is supported by Clang but not GCC.
 #if defined(__GNUC__) && defined(MEMORY_SANITIZER)
 #define ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY __attribute__((no_sanitize_memory))
@@ -207,8 +247,8 @@
 #endif
 
 // ABSL_ATTRIBUTE_NO_SANITIZE_THREAD
-// Tell ThreadSanitizer to not instrument a given function.
-// If you are adding this attribute, please cc dynamic-tools@ on the cl.
+//
+// Tells the ThreadSanitizer to not instrument a given function.
 // NOTE: GCC supports ThreadSanitizer(tsan) since 4.8.
 // https://gcc.gnu.org/gcc-4.8/changes.html
 #if defined(__GNUC__) && defined(THREAD_SANITIZER)
@@ -218,7 +258,8 @@
 #endif
 
 // ABSL_ATTRIBUTE_NO_SANITIZE_UNDEFINED
-// Tell UndefinedSanitizer to ignore a given function. Useful for cases
+//
+// Tells the UndefinedSanitizer to ignore a given function. Useful for cases
 // where certain behavior (eg. devision by zero) is being used intentionally.
 // NOTE: GCC supports UndefinedBehaviorSanitizer(ubsan) since 4.9.
 // https://gcc.gnu.org/gcc-4.9/changes.html
@@ -231,7 +272,8 @@
 #endif
 
 // ABSL_ATTRIBUTE_NO_SANITIZE_CFI
-// Tell ControlFlowIntegrity sanitizer to not instrument a given function.
+//
+// Tells the ControlFlowIntegrity sanitizer to not instrument a given function.
 // See https://clang.llvm.org/docs/ControlFlowIntegrity.html for details.
 #if defined(__GNUC__) && defined(CONTROL_FLOW_INTEGRITY)
 #define ABSL_ATTRIBUTE_NO_SANITIZE_CFI __attribute__((no_sanitize("cfi")))
@@ -239,33 +281,42 @@
 #define ABSL_ATTRIBUTE_NO_SANITIZE_CFI
 #endif
 
-// ABSL_ATTRIBUTE_SECTION
-// Labeled sections are not supported on Darwin/iOS.
+// ABSL_HAVE_ATTRIBUTE_SECTION
+//
+// Indicates whether labeled sections are supported. Labeled sections are not
+// supported on Darwin/iOS.
 #ifdef ABSL_HAVE_ATTRIBUTE_SECTION
 #error ABSL_HAVE_ATTRIBUTE_SECTION cannot be directly set
 #elif (ABSL_HAVE_ATTRIBUTE(section) ||                \
        (defined(__GNUC__) && !defined(__clang__))) && \
     !defined(__APPLE__)
 #define ABSL_HAVE_ATTRIBUTE_SECTION 1
+
+// ABSL_ATTRIBUTE_SECTION
 //
-// Tell the compiler/linker to put a given function into a section and define
-// "__start_ ## name" and "__stop_ ## name" symbols to bracket the section.
-// This functionality is supported by GNU linker.
-// Any function with ABSL_ATTRIBUTE_SECTION must not be inlined, or it will
-// be placed into whatever section its caller is placed into.
+// Tells the compiler/linker to put a given function into a section and define
+// `__start_ ## name` and `__stop_ ## name` symbols to bracket the section.
+// This functionality is supported by GNU linker.  Any function annotated with
+// `ABSL_ATTRIBUTE_SECTION` must not be inlined, or it will be placed into
+// whatever section its caller is placed into.
 //
 #ifndef ABSL_ATTRIBUTE_SECTION
 #define ABSL_ATTRIBUTE_SECTION(name) \
   __attribute__((section(#name))) __attribute__((noinline))
 #endif
-// Tell the compiler/linker to put a given variable into a section and define
-// "__start_ ## name" and "__stop_ ## name" symbols to bracket the section.
+
+// ABSL_ATTRIBUTE_SECTION_VARIABLE
+//
+// Tells the compiler/linker to put a given variable into a section and define
+// `__start_ ## name` and `__stop_ ## name` symbols to bracket the section.
 // This functionality is supported by GNU linker.
 #ifndef ABSL_ATTRIBUTE_SECTION_VARIABLE
 #define ABSL_ATTRIBUTE_SECTION_VARIABLE(name) __attribute__((section(#name)))
 #endif
+
+// ABSL_DECLARE_ATTRIBUTE_SECTION_VARS
 //
-// Weak section declaration to be used as a global declaration
+// A weak section declaration to be used as a global declaration
 // for ABSL_ATTRIBUTE_SECTION_START|STOP(name) to compile and link
 // even without functions with ABSL_ATTRIBUTE_SECTION(name).
 // ABSL_DEFINE_ATTRIBUTE_SECTION should be in the exactly one file; it's
@@ -281,7 +332,9 @@
 #define ABSL_DEFINE_ATTRIBUTE_SECTION_VARS(name)
 #endif
 
-// Return void* pointers to start/end of a section of code with
+// ABSL_ATTRIBUTE_SECTION_START
+//
+// Returns `void*` pointers to start/end of a section of code with
 // functions having ABSL_ATTRIBUTE_SECTION(name).
 // Returns 0 if no such functions exist.
 // One must ABSL_DECLARE_ATTRIBUTE_SECTION_VARS(name) for this to compile and
@@ -306,6 +359,7 @@
 #endif  // ABSL_ATTRIBUTE_SECTION
 
 // ABSL_ATTRIBUTE_STACK_ALIGN_FOR_OLD_LIBC
+//
 // Support for aligning the stack on 32-bit x86.
 #if ABSL_HAVE_ATTRIBUTE(force_align_arg_pointer) || \
     (defined(__GNUC__) && !defined(__clang__))
@@ -326,10 +380,13 @@
 #endif
 
 // ABSL_MUST_USE_RESULT
-// Tell the compiler to warn about unused return values for functions declared
+//
+// Tells the compiler to warn about unused return values for functions declared
 // with this macro. The macro must appear as the very first part of a function
 // declaration or definition:
 //
+// Example:
+//
 //   ABSL_MUST_USE_RESULT Sprocket* AllocateSprocket();
 //
 // This placement has the broadest compatibility with GCC, Clang, and MSVC, with
@@ -350,10 +407,14 @@
 #endif
 
 // ABSL_ATTRIBUTE_HOT, ABSL_ATTRIBUTE_COLD
-// Tell GCC that a function is hot or cold. GCC can use this information to
+//
+// Tells GCC that a function is hot or cold. GCC can use this information to
 // improve static analysis, i.e. a conditional branch to a cold function
 // is likely to be not-taken.
-// This annotation is used for function declarations, e.g.:
+// This annotation is used for function declarations.
+//
+// Example:
+//
 //   int foo() ABSL_ATTRIBUTE_HOT;
 #if ABSL_HAVE_ATTRIBUTE(hot) || (defined(__GNUC__) && !defined(__clang__))
 #define ABSL_ATTRIBUTE_HOT __attribute__((hot))
@@ -382,12 +443,12 @@
 //
 // These attributes only take effect when the following conditions are met:
 //
-//   - The file/target is built in at least C++11 mode, with a Clang compiler
-//   that supports XRay attributes.
-//   - The file/target is built with the -fxray-instrument flag set for the
-//   Clang/LLVM compiler.
-//   - The function is defined in the translation unit (the compiler honors the
-//   attribute in either the definition or the declaration, and must match).
+//   * The file/target is built in at least C++11 mode, with a Clang compiler
+//     that supports XRay attributes.
+//   * The file/target is built with the -fxray-instrument flag set for the
+//     Clang/LLVM compiler.
+//   * The function is defined in the translation unit (the compiler honors the
+//     attribute in either the definition or the declaration, and must match).
 //
 // There are cases when, even when building with XRay instrumentation, users
 // might want to control specifically which functions are instrumented for a
@@ -422,7 +483,8 @@
 // -----------------------------------------------------------------------------
 
 // ABSL_ATTRIBUTE_UNUSED
-// Prevent the compiler from complaining about or optimizing away variables
+//
+// Prevents the compiler from complaining about or optimizing away variables
 // that appear unused.
 #if ABSL_HAVE_ATTRIBUTE(unused) || (defined(__GNUC__) && !defined(__clang__))
 #undef ABSL_ATTRIBUTE_UNUSED
@@ -430,8 +492,10 @@
 #else
 #define ABSL_ATTRIBUTE_UNUSED
 #endif
+
 // ABSL_ATTRIBUTE_INITIAL_EXEC
-// Tell the compiler to use "initial-exec" mode for a thread-local variable.
+//
+// Tells the compiler to use "initial-exec" mode for a thread-local variable.
 // See http://people.redhat.com/drepper/tls.pdf for the gory details.
 #if ABSL_HAVE_ATTRIBUTE(tls_model) || (defined(__GNUC__) && !defined(__clang__))
 #define ABSL_ATTRIBUTE_INITIAL_EXEC __attribute__((tls_model("initial-exec")))
@@ -440,7 +504,8 @@
 #endif
 
 // ABSL_ATTRIBUTE_PACKED
-// Prevent the compiler from padding a structure to natural alignment
+//
+// Prevents the compiler from padding a structure to natural alignment
 #if ABSL_HAVE_ATTRIBUTE(packed) || (defined(__GNUC__) && !defined(__clang__))
 #define ABSL_ATTRIBUTE_PACKED __attribute__((__packed__))
 #else
@@ -448,15 +513,16 @@
 #endif
 
 // ABSL_CONST_INIT
-// A variable declaration annotated with the ABSL_CONST_INIT attribute will
+//
+// A variable declaration annotated with the `ABSL_CONST_INIT` attribute will
 // not compile (on supported platforms) unless the variable has a constant
 // initializer. This is useful for variables with static and thread storage
 // duration, because it guarantees that they will not suffer from the so-called
 // "static init order fiasco".
 //
-// Sample usage:
+// Example:
 //
-// ABSL_CONST_INIT static MyType my_var = MakeMyType(...);
+//   ABSL_CONST_INIT static MyType my_var = MakeMyType(...);
 //
 // Note that this attribute is redundant if the variable is declared constexpr.
 #if ABSL_HAVE_CPP_ATTRIBUTE(clang::require_constant_initialization)