Move Abseil to C++14 minimum

Adds policy checks the raise the minimum C++ version to C++14
and the minimum GCC version to GCC 5

Updates the docs to indicate the C++14 minimum.

PiperOrigin-RevId: 459401288
Change-Id: I18878f0e13001c57e97e26ad7c9a9c9c12c39265

5 files changed, 29 insertions, 26 deletions

diff --git a/CMake/AbseilHelpers.cmake b/CMake/AbseilHelpers.cmake
index 6d03381b..ebe9ddc8 100644
--- a/CMake/AbseilHelpers.cmake
+++ b/CMake/AbseilHelpers.cmake
@@ -258,10 +258,10 @@ Cflags: -I\${includedir}${PC_CFLAGS}\n")
     endif()
 
     if(ABSL_PROPAGATE_CXX_STD)
-      # Abseil libraries require C++11 as the current minimum standard.
+      # Abseil libraries require C++14 as the current minimum standard.
       # Top-level application CMake projects should ensure a consistent C++
       # standard for all compiled sources by setting CMAKE_CXX_STANDARD.
-      target_compile_features(${_NAME} PUBLIC cxx_std_11)
+      target_compile_features(${_NAME} PUBLIC cxx_std_14)
     else()
       # Note: This is legacy (before CMake 3.8) behavior. Setting the
       # target-level CXX_STANDARD property to ABSL_CXX_STANDARD (which is
@@ -306,10 +306,10 @@ Cflags: -I\${includedir}${PC_CFLAGS}\n")
     target_compile_definitions(${_NAME} INTERFACE ${ABSL_CC_LIB_DEFINES})
 
     if(ABSL_PROPAGATE_CXX_STD)
-      # Abseil libraries require C++11 as the current minimum standard.
+      # Abseil libraries require C++14 as the current minimum standard.
       # Top-level application CMake projects should ensure a consistent C++
       # standard for all compiled sources by setting CMAKE_CXX_STANDARD.
-      target_compile_features(${_NAME} INTERFACE cxx_std_11)
+      target_compile_features(${_NAME} INTERFACE cxx_std_14)
 
       # (INTERFACE libraries can't have the CXX_STANDARD property set, so there
       # is no legacy behavior else case).
@@ -418,10 +418,10 @@ function(absl_cc_test)
   set_property(TARGET ${_NAME} PROPERTY FOLDER ${ABSL_IDE_FOLDER}/test)
 
   if(ABSL_PROPAGATE_CXX_STD)
-    # Abseil libraries require C++11 as the current minimum standard.
+    # Abseil libraries require C++14 as the current minimum standard.
     # Top-level application CMake projects should ensure a consistent C++
     # standard for all compiled sources by setting CMAKE_CXX_STANDARD.
-    target_compile_features(${_NAME} PUBLIC cxx_std_11)
+    target_compile_features(${_NAME} PUBLIC cxx_std_14)
   else()
     # Note: This is legacy (before CMake 3.8) behavior. Setting the
     # target-level CXX_STANDARD property to ABSL_CXX_STANDARD (which is
diff --git a/CMake/README.md b/CMake/README.md
index 8134615e..0be3b926 100644
--- a/CMake/README.md
+++ b/CMake/README.md
@@ -43,8 +43,8 @@ cmake_minimum_required(VERSION 3.8.2)
 project(my_app_project)
 
 # Pick the C++ standard to compile with.
-# Abseil currently supports C++11, C++14, and C++17.
-set(CMAKE_CXX_STANDARD 11)
+# Abseil currently supports C++14, C++17, and C++20.
+set(CMAKE_CXX_STANDARD 14)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 add_subdirectory(abseil-cpp)
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8a20d04a..10acf3b7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -64,7 +64,7 @@ else()
 endif()
 
 option(ABSL_PROPAGATE_CXX_STD
-  "Use CMake C++ standard meta features (e.g. cxx_std_11) that propagate to targets that link to Abseil"
+  "Use CMake C++ standard meta features (e.g. cxx_std_14) that propagate to targets that link to Abseil"
   OFF)  # TODO: Default to ON for CMake 3.8 and greater.
 if((${CMAKE_VERSION} VERSION_GREATER_EQUAL 3.8) AND (NOT ABSL_PROPAGATE_CXX_STD))
   message(WARNING "A future Abseil release will default ABSL_PROPAGATE_CXX_STD to ON for CMake 3.8 and up. We recommend enabling this option to ensure your project still builds correctly.")
diff --git a/README.md b/README.md
index db3a7b44..89790021 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # Abseil - C++ Common Libraries
 
 The repository contains the Abseil C++ library code. Abseil is an open-source
-collection of C++ code (compliant to C++11) designed to augment the C++
+collection of C++ code (compliant to C++14) designed to augment the C++
 standard library.
 
 ## Table of Contents
@@ -85,13 +85,14 @@ Abseil contains the following C++ library components:
   <br /> The `hash` library contains the hashing framework and default hash
   functor implementations for hashable types in Abseil.
 * [`memory`](absl/memory/)
-  <br /> The `memory` library contains C++11-compatible versions of
-  `std::make_unique()` and related memory management facilities.
+  <br /> The `memory` library contains memory management facilities that
+  augment C++'s `<memory>` library.
 * [`meta`](absl/meta/)
-  <br /> The `meta` library contains C++11-compatible versions of type checks
+  <br /> The `meta` library contains compatible versions of type checks
   available within C++14 and C++17 versions of the C++ `<type_traits>` library.
 * [`numeric`](absl/numeric/)
-  <br /> The `numeric` library contains C++11-compatible 128-bit integers.
+  <br /> The `numeric` library contains 128-bit integer types as well as
+  implementations of C++20's bitwise math functions.
 * [`profiling`](absl/profiling/)
   <br /> The `profiling` library contains utility code for profiling C++
   entities.  It is currently a private dependency of other Abseil libraries.
@@ -100,7 +101,7 @@ Abseil contains the following C++ library components:
   `absl::Status` and `absl::StatusOr<T>`.
 * [`strings`](absl/strings/)
   <br /> The `strings` library contains a variety of strings routines and
-  utilities, including a C++11-compatible version of the C++17
+  utilities, including a C++14-compatible version of the C++17
   `std::string_view` type.
 * [`synchronization`](absl/synchronization/)
   <br /> The `synchronization` library contains concurrency primitives (Abseil's
@@ -112,7 +113,7 @@ Abseil contains the following C++ library components:
   time zones.
 * [`types`](absl/types/)
   <br /> The `types` library contains non-container utility types, like a
-  C++11-compatible version of the C++17 `std::optional` type.
+  C++14-compatible version of the C++17 `std::optional` type.
 * [`utility`](absl/utility/)
   <br /> The `utility` library contains utility and helper code.
 
diff --git a/absl/base/policy_checks.h b/absl/base/policy_checks.h
index 06b32439..d13073c8 100644
--- a/absl/base/policy_checks.h
+++ b/absl/base/policy_checks.h
@@ -50,11 +50,11 @@
 #error "This package requires Visual Studio 2015 Update 2 or higher."
 #endif
 
-// We support gcc 4.7 and later.
+// We support gcc 5 and later.
 // This minimum will go up.
 #if defined(__GNUC__) && !defined(__clang__)
-#if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 7)
-#error "This package requires gcc 4.7 or higher."
+#if __GNUC__ < 5
+#error "This package requires gcc 5 or higher."
 #endif
 #endif
 
@@ -69,13 +69,15 @@
 // C++ Version Check
 // -----------------------------------------------------------------------------
 
-// Enforce C++11 as the minimum.  Note that Visual Studio has not
-// advanced __cplusplus despite being good enough for our purposes, so
-// so we exempt it from the check.
-#if defined(__cplusplus) && !defined(_MSC_VER)
-#if __cplusplus < 201103L
-#error "C++ versions less than C++11 are not supported."
-#endif
+// Enforce C++14 as the minimum.
+#if defined(_MSVC_LANG)
+#if _MSVC_LANG < 201402L
+#error "C++ versions less than C++14 are not supported."
+#endif  // _MSVC_LANG < 201402L
+#elif defined(__cplusplus)
+#if __cplusplus < 201402L
+#error "C++ versions less than C++14 are not supported."
+#endif  // __cplusplus < 201402L
 #endif
 
 // -----------------------------------------------------------------------------