Export of internal Abseil changes.

--
22fa219d17b2281c0695642830c4300711bd65ea by CJ Johnson <johnsoncj@google.com>:

Rearrange the private method declarations in InlinedVector

PiperOrigin-RevId: 224202447

--
eed3c9f488f23b521bee41d3683eb6cc22517ded by Derek Mauro <dmauro@google.com>:

Fix leak_check target (it was always a no-op when LSAN isn't available).
Fixes https://github.com/abseil/abseil-cpp/issues/232

PiperOrigin-RevId: 224201634

--
fc08039e175204b14a9561f618fcfc0234586801 by Greg Falcon <gfalcon@google.com>:

Add parens around more invocations of min() and max() missed in my prior CL.

PiperOrigin-RevId: 224162430

--
0ec5476a8293c7796cd84928a1a558b14f14f222 by Abseil Team <absl-team@google.com>:

Update absl/numeric/CMakeLists.txt to use new functions
i.e. absl_cc_(library|test)

PiperOrigin-RevId: 224139165

--
2b46aa6fabb20c589661f8bbc84030ecf39ce394 by Abseil Team <absl-team@google.com>:

Update absl/meta/CMakeLists.txt to use new functions
i.e. absl_cc_(library|test)

PiperOrigin-RevId: 224117258

--
6c951c798f8c6903bd8793a8a4b5f69244be8aa9 by Abseil Team <absl-team@google.com>:

Fix 2 Unused C++ BUILD Dependencies

PiperOrigin-RevId: 224070093

--
0ee7bd191708708f91fc5209c197fd93f6e4a8b3 by Greg Falcon <gfalcon@google.com>:

Inside Abseil headers, wrap most invocations of methods and functions named `min` and `max` in parentheses, for better interoperability with Windows toolchains.

CCTZ fixes will appear in a follow-up CL.

PiperOrigin-RevId: 224051960

--
f562f56577b84a8bc07e5873775c01d068531bca by Jon Cohen <cohenjon@google.com>:

Generate Abseil compile options.  The single source of truth is now absl/copts/copts.py

The way this works goes something like this:
copts.py acts as the configuration file.  We use python because unlike JSON it allows comments.  It has two maps in it: one from names to external flags, and one from names to internal flags.

generate_copts.py imports the maps and loops through them to write GENERATED_copts.bzl and GENERATED_AbseilCopts.cmake

AbseilConfigureCopts.cmake and configure_copts.bzl import their respective copts args and set the platform-appropriate copts into ABSL_DEFAULT_COPTS, ABSL_TEST_COPTS, ABSL_EXCEPTIONS_FLAG, and ABSL_EXCEPTIONS_LINKOPTS

For Bazel, each BUILD file load()s configure_copts.bzl

For CMake, AbseilHelpers.cmake include()s AbseilConfigureCopts.cmake to get the final copts and both inserts them as needed into legacy target rules and also makes them available to the rest of our CMakeLists.txt file.  We may instead want to include() AbseilConfigureCopts.cmake directly into each CMakeLists.txt file for consistency, but I'm not sure what the deal is with cmake and include guards, or if they are even needed.  That's also not as idiomatic -- CMake tends to use directory scope where globals set at a higher level CMakeLists.txt file are used in the subdirectory CMakeLists.txt files.

PiperOrigin-RevId: 224039419

--
f7402f6bb65037e668a7355f0a003f5c05a3b6a7 by Abseil Team <absl-team@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 224036622
GitOrigin-RevId: 22fa219d17b2281c0695642830c4300711bd65ea
Change-Id: I6b505360539ff2aef8aa30c51a5f7d55db1c75cf

6 files changed, 600 insertions, 0 deletions

diff --git a/absl/copts/AbseilConfigureCopts.cmake b/absl/copts/AbseilConfigureCopts.cmake
new file mode 100644
index 00000000..6fde7754
--- /dev/null
+++ b/absl/copts/AbseilConfigureCopts.cmake
@@ -0,0 +1,34 @@
+# See absl/copts/copts.py and absl/copts/generate_copts.py
+include(GENERATED_AbseilCopts)
+
+if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
+  set(ABSL_DEFAULT_COPTS "${GCC_FLAGS}")
+  set(ABSL_TEST_COPTS "${GCC_FLAGS};${GCC_TEST_FLAGS}")
+  set(ABSL_EXCEPTIONS_FLAG "${GCC_EXCEPTIONS_FLAGS}")
+elseif("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+  # MATCHES so we get both Clang and AppleClang
+  set(ABSL_DEFAULT_COPTS "${LLVM_FLAGS}")
+  set(ABSL_TEST_COPTS "${LLVM_FLAGS};${LLVM_TEST_FLAGS}")
+  set(ABSL_EXCEPTIONS_FLAG "${LLVM_EXCEPTIONS_FLAGS}")
+elseif("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
+  set(ABSL_DEFAULT_COPTS "${MSVC_FLAGS}")
+  set(ABSL_TEST_COPTS "${MSVC_FLAGS};${MSVC_TEST_FLAGS}")
+  set(ABSL_EXCEPTIONS_FLAG "${MSVC_EXCEPTIONS_FLAGS}")
+else()
+  message(WARNING "Unknown compiler: ${CMAKE_CXX_COMPILER}.  Building with no default flags")
+  set(ABSL_DEFAULT_COPTS "")
+  set(ABSL_TEST_COPTS "")
+  set(ABSL_EXCEPTIONS_FLAG "")
+endif()
+
+# This flag is used internally for Bazel builds and is kept here for consistency
+set(ABSL_EXCEPTIONS_FLAG_LINKOPTS "")
+
+if("${CMAKE_CXX_STANDARD}" EQUAL 98)
+  message(FATAL_ERROR "Abseil requires at least C++11")
+elseif(NOT "${CMAKE_CXX_STANDARD}")
+  message(STATUS "No CMAKE_CXX_STANDARD set, assuming 11")
+  set(ABSL_CXX_STANDARD 11)
+else()
+  set(ABSL_CXX_STANDARD "${CMAKE_CXX_STANDARD}")
+endif()
\ No newline at end of file
diff --git a/absl/copts/GENERATED_AbseilCopts.cmake b/absl/copts/GENERATED_AbseilCopts.cmake
new file mode 100644
index 00000000..e6678a4f
--- /dev/null
+++ b/absl/copts/GENERATED_AbseilCopts.cmake
@@ -0,0 +1,130 @@
+# GENERATED! DO NOT MANUALLY EDIT THIS FILE.
+#
+# (1) Edit absl/copts/copts.py.
+# (2) Run `python <path_to_absl>/copts/generate_copts.py`.
+
+list(APPEND GCC_EXCEPTIONS_FLAGS
+    "-fexceptions"
+)
+
+list(APPEND GCC_FLAGS
+    "-Wall"
+    "-Wextra"
+    "-Wcast-qual"
+    "-Wconversion-null"
+    "-Wmissing-declarations"
+    "-Woverlength-strings"
+    "-Wpointer-arith"
+    "-Wunused-local-typedefs"
+    "-Wunused-result"
+    "-Wvarargs"
+    "-Wvla"
+    "-Wwrite-strings"
+    "-Wno-sign-compare"
+)
+
+list(APPEND GCC_TEST_FLAGS
+    "-Wno-conversion-null"
+    "-Wno-missing-declarations"
+    "-Wno-sign-compare"
+    "-Wno-unused-function"
+    "-Wno-unused-parameter"
+    "-Wno-unused-private-field"
+)
+
+list(APPEND LLVM_EXCEPTIONS_FLAGS
+    "-fexceptions"
+)
+
+list(APPEND LLVM_FLAGS
+    "-Wall"
+    "-Wextra"
+    "-Weverything"
+    "-Wno-c++98-compat-pedantic"
+    "-Wno-conversion"
+    "-Wno-covered-switch-default"
+    "-Wno-deprecated"
+    "-Wno-disabled-macro-expansion"
+    "-Wno-double-promotion"
+    "-Wno-comma"
+    "-Wno-extra-semi"
+    "-Wno-packed"
+    "-Wno-padded"
+    "-Wno-sign-compare"
+    "-Wno-float-conversion"
+    "-Wno-float-equal"
+    "-Wno-format-nonliteral"
+    "-Wno-gcc-compat"
+    "-Wno-global-constructors"
+    "-Wno-exit-time-destructors"
+    "-Wno-nested-anon-types"
+    "-Wno-non-modular-include-in-module"
+    "-Wno-old-style-cast"
+    "-Wno-range-loop-analysis"
+    "-Wno-reserved-id-macro"
+    "-Wno-shorten-64-to-32"
+    "-Wno-switch-enum"
+    "-Wno-thread-safety-negative"
+    "-Wno-undef"
+    "-Wno-unknown-warning-option"
+    "-Wno-unreachable-code"
+    "-Wno-unused-macros"
+    "-Wno-weak-vtables"
+    "-Wbitfield-enum-conversion"
+    "-Wbool-conversion"
+    "-Wconstant-conversion"
+    "-Wenum-conversion"
+    "-Wint-conversion"
+    "-Wliteral-conversion"
+    "-Wnon-literal-null-conversion"
+    "-Wnull-conversion"
+    "-Wobjc-literal-conversion"
+    "-Wno-sign-conversion"
+    "-Wstring-conversion"
+)
+
+list(APPEND LLVM_TEST_FLAGS
+    "-Wno-c99-extensions"
+    "-Wno-missing-noreturn"
+    "-Wno-missing-prototypes"
+    "-Wno-missing-variable-declarations"
+    "-Wno-null-conversion"
+    "-Wno-shadow"
+    "-Wno-shift-sign-overflow"
+    "-Wno-sign-compare"
+    "-Wno-unused-function"
+    "-Wno-unused-member-function"
+    "-Wno-unused-parameter"
+    "-Wno-unused-private-field"
+    "-Wno-unused-template"
+    "-Wno-used-but-marked-unused"
+    "-Wno-zero-as-null-pointer-constant"
+    "-Wno-gnu-zero-variadic-macro-arguments"
+)
+
+list(APPEND MSVC_EXCEPTIONS_FLAGS
+    "/U_HAS_EXCEPTIONS"
+    "/D_HAS_EXCEPTIONS=1"
+    "/EHsc"
+)
+
+list(APPEND MSVC_FLAGS
+    "/W3"
+    "/wd4005"
+    "/wd4068"
+    "/wd4180"
+    "/wd4244"
+    "/wd4267"
+    "/wd4800"
+    "/DNOMINMAX"
+    "/DWIN32_LEAN_AND_MEAN"
+    "/D_CRT_SECURE_NO_WARNINGS"
+    "/D_SCL_SECURE_NO_WARNINGS"
+    "/D_ENABLE_EXTENDED_ALIGNED_STORAGE"
+)
+
+list(APPEND MSVC_TEST_FLAGS
+    "/wd4018"
+    "/wd4101"
+    "/wd4503"
+)
diff --git a/absl/copts/GENERATED_copts.bzl b/absl/copts/GENERATED_copts.bzl
new file mode 100644
index 00000000..134797da
--- /dev/null
+++ b/absl/copts/GENERATED_copts.bzl
@@ -0,0 +1,131 @@
+"""GENERATED! DO NOT MANUALLY EDIT THIS FILE.
+
+(1) Edit absl/copts/copts.py.
+(2) Run `python <path_to_absl>/copts/generate_copts.py`.
+"""
+
+GCC_EXCEPTIONS_FLAGS = [
+    "-fexceptions",
+]
+
+GCC_FLAGS = [
+    "-Wall",
+    "-Wextra",
+    "-Wcast-qual",
+    "-Wconversion-null",
+    "-Wmissing-declarations",
+    "-Woverlength-strings",
+    "-Wpointer-arith",
+    "-Wunused-local-typedefs",
+    "-Wunused-result",
+    "-Wvarargs",
+    "-Wvla",
+    "-Wwrite-strings",
+    "-Wno-sign-compare",
+]
+
+GCC_TEST_FLAGS = [
+    "-Wno-conversion-null",
+    "-Wno-missing-declarations",
+    "-Wno-sign-compare",
+    "-Wno-unused-function",
+    "-Wno-unused-parameter",
+    "-Wno-unused-private-field",
+]
+
+LLVM_EXCEPTIONS_FLAGS = [
+    "-fexceptions",
+]
+
+LLVM_FLAGS = [
+    "-Wall",
+    "-Wextra",
+    "-Weverything",
+    "-Wno-c++98-compat-pedantic",
+    "-Wno-conversion",
+    "-Wno-covered-switch-default",
+    "-Wno-deprecated",
+    "-Wno-disabled-macro-expansion",
+    "-Wno-double-promotion",
+    "-Wno-comma",
+    "-Wno-extra-semi",
+    "-Wno-packed",
+    "-Wno-padded",
+    "-Wno-sign-compare",
+    "-Wno-float-conversion",
+    "-Wno-float-equal",
+    "-Wno-format-nonliteral",
+    "-Wno-gcc-compat",
+    "-Wno-global-constructors",
+    "-Wno-exit-time-destructors",
+    "-Wno-nested-anon-types",
+    "-Wno-non-modular-include-in-module",
+    "-Wno-old-style-cast",
+    "-Wno-range-loop-analysis",
+    "-Wno-reserved-id-macro",
+    "-Wno-shorten-64-to-32",
+    "-Wno-switch-enum",
+    "-Wno-thread-safety-negative",
+    "-Wno-undef",
+    "-Wno-unknown-warning-option",
+    "-Wno-unreachable-code",
+    "-Wno-unused-macros",
+    "-Wno-weak-vtables",
+    "-Wbitfield-enum-conversion",
+    "-Wbool-conversion",
+    "-Wconstant-conversion",
+    "-Wenum-conversion",
+    "-Wint-conversion",
+    "-Wliteral-conversion",
+    "-Wnon-literal-null-conversion",
+    "-Wnull-conversion",
+    "-Wobjc-literal-conversion",
+    "-Wno-sign-conversion",
+    "-Wstring-conversion",
+]
+
+LLVM_TEST_FLAGS = [
+    "-Wno-c99-extensions",
+    "-Wno-missing-noreturn",
+    "-Wno-missing-prototypes",
+    "-Wno-missing-variable-declarations",
+    "-Wno-null-conversion",
+    "-Wno-shadow",
+    "-Wno-shift-sign-overflow",
+    "-Wno-sign-compare",
+    "-Wno-unused-function",
+    "-Wno-unused-member-function",
+    "-Wno-unused-parameter",
+    "-Wno-unused-private-field",
+    "-Wno-unused-template",
+    "-Wno-used-but-marked-unused",
+    "-Wno-zero-as-null-pointer-constant",
+    "-Wno-gnu-zero-variadic-macro-arguments",
+]
+
+MSVC_EXCEPTIONS_FLAGS = [
+    "/U_HAS_EXCEPTIONS",
+    "/D_HAS_EXCEPTIONS=1",
+    "/EHsc",
+]
+
+MSVC_FLAGS = [
+    "/W3",
+    "/wd4005",
+    "/wd4068",
+    "/wd4180",
+    "/wd4244",
+    "/wd4267",
+    "/wd4800",
+    "/DNOMINMAX",
+    "/DWIN32_LEAN_AND_MEAN",
+    "/D_CRT_SECURE_NO_WARNINGS",
+    "/D_SCL_SECURE_NO_WARNINGS",
+    "/D_ENABLE_EXTENDED_ALIGNED_STORAGE",
+]
+
+MSVC_TEST_FLAGS = [
+    "/wd4018",
+    "/wd4101",
+    "/wd4503",
+]
diff --git a/absl/copts/configure_copts.bzl b/absl/copts/configure_copts.bzl
new file mode 100644
index 00000000..57cd3f62
--- /dev/null
+++ b/absl/copts/configure_copts.bzl
@@ -0,0 +1,42 @@
+"""absl specific copts.
+
+This file simply selects the correct options from the generated files.  To
+change Abseil copts, edit absl/copts/copts.py
+"""
+
+load(
+    "//absl:copts/GENERATED_copts.bzl",
+    "GCC_EXCEPTIONS_FLAGS",
+    "GCC_FLAGS",
+    "GCC_TEST_FLAGS",
+    "LLVM_EXCEPTIONS_FLAGS",
+    "LLVM_FLAGS",
+    "LLVM_TEST_FLAGS",
+    "MSVC_EXCEPTIONS_FLAGS",
+    "MSVC_FLAGS",
+    "MSVC_TEST_FLAGS",
+)
+
+ABSL_DEFAULT_COPTS = select({
+    "//absl:windows": MSVC_FLAGS,
+    "//absl:llvm_compiler": LLVM_FLAGS,
+    "//conditions:default": GCC_FLAGS,
+})
+
+# in absence of modules (--compiler=gcc or -c opt), cc_tests leak their copts
+# to their (included header) dependencies and fail to build outside absl
+ABSL_TEST_COPTS = ABSL_DEFAULT_COPTS + select({
+    "//absl:windows": MSVC_TEST_FLAGS,
+    "//absl:llvm_compiler": LLVM_TEST_FLAGS,
+    "//conditions:default": GCC_TEST_FLAGS,
+})
+
+ABSL_EXCEPTIONS_FLAG = select({
+    "//absl:windows": MSVC_EXCEPTIONS_FLAGS,
+    "//absl:llvm_compiler": LLVM_EXCEPTIONS_FLAGS,
+    "//conditions:default": GCC_EXCEPTIONS_FLAGS,
+})
+
+ABSL_EXCEPTIONS_FLAG_LINKOPTS = select({
+    "//conditions:default": [],
+})
diff --git a/absl/copts/copts.py b/absl/copts/copts.py
new file mode 100644
index 00000000..2fbba883
--- /dev/null
+++ b/absl/copts/copts.py
@@ -0,0 +1,156 @@
+"""Abseil compiler options.
+
+This is the source of truth for Abseil compiler options.  To modify Abseil
+compilation options:
+
+  (1) Edit the appropriate list in this file.
+  (2) Run `python <path_to_absl>/copts/generate_copts.py`.
+
+The generated copts are consumed by configure_copts.bzl and
+AbseilConfigureCopts.cmake.
+"""
+
+import collections  # absl:google-only(used for internal flags)
+
+COPT_VARS = {
+    "GCC_FLAGS": [
+        "-Wall",
+        "-Wextra",
+        "-Wcast-qual",
+        "-Wconversion-null",
+        "-Wmissing-declarations",
+        "-Woverlength-strings",
+        "-Wpointer-arith",
+        "-Wunused-local-typedefs",
+        "-Wunused-result",
+        "-Wvarargs",
+        "-Wvla",  # variable-length array
+        "-Wwrite-strings",
+        # Google style does not use unsigned integers, though STL containers
+        # have unsigned types.
+        "-Wno-sign-compare",
+    ],
+    "GCC_TEST_FLAGS": [
+        "-Wno-conversion-null",
+        "-Wno-missing-declarations",
+        "-Wno-sign-compare",
+        "-Wno-unused-function",
+        "-Wno-unused-parameter",
+        "-Wno-unused-private-field",
+    ],
+    "GCC_EXCEPTIONS_FLAGS": ["-fexceptions"],
+
+    # Docs on single flags is preceded by a comment.
+    # Docs on groups of flags is preceded by ###.
+    "LLVM_FLAGS": [
+        "-Wall",
+        "-Wextra",
+        "-Weverything",
+        # Abseil does not support C++98
+        "-Wno-c++98-compat-pedantic",
+        # Turns off all implicit conversion warnings. Most are re-enabled below.
+        "-Wno-conversion",
+        "-Wno-covered-switch-default",
+        "-Wno-deprecated",
+        "-Wno-disabled-macro-expansion",
+        "-Wno-double-promotion",
+        ###
+        # Turned off as they include valid C++ code.
+        "-Wno-comma",
+        "-Wno-extra-semi",
+        "-Wno-packed",
+        "-Wno-padded",
+        ###
+        # Google style does not use unsigned integers, though STL containers
+        # have unsigned types.
+        "-Wno-sign-compare",
+        ###
+        "-Wno-float-conversion",
+        "-Wno-float-equal",
+        "-Wno-format-nonliteral",
+        # Too aggressive: warns on Clang extensions enclosed in Clang-only
+        # compilation paths.
+        "-Wno-gcc-compat",
+        ###
+        # Some internal globals are necessary. Don't do this at home.
+        "-Wno-global-constructors",
+        "-Wno-exit-time-destructors",
+        ###
+        "-Wno-nested-anon-types",
+        "-Wno-non-modular-include-in-module",
+        "-Wno-old-style-cast",
+        # Warns on preferred usage of non-POD types such as string_view
+        "-Wno-range-loop-analysis",
+        "-Wno-reserved-id-macro",
+        "-Wno-shorten-64-to-32",
+        "-Wno-switch-enum",
+        "-Wno-thread-safety-negative",
+        "-Wno-undef",
+        "-Wno-unknown-warning-option",
+        "-Wno-unreachable-code",
+        # Causes warnings on include guards
+        "-Wno-unused-macros",
+        "-Wno-weak-vtables",
+        ###
+        # Implicit conversion warnings turned off by -Wno-conversion
+        # which are re-enabled below.
+        "-Wbitfield-enum-conversion",
+        "-Wbool-conversion",
+        "-Wconstant-conversion",
+        "-Wenum-conversion",
+        "-Wint-conversion",
+        "-Wliteral-conversion",
+        "-Wnon-literal-null-conversion",
+        "-Wnull-conversion",
+        "-Wobjc-literal-conversion",
+        "-Wno-sign-conversion",
+        "-Wstring-conversion",
+    ],
+    "LLVM_TEST_FLAGS": [
+        "-Wno-c99-extensions",
+        "-Wno-missing-noreturn",
+        "-Wno-missing-prototypes",
+        "-Wno-missing-variable-declarations",
+        "-Wno-null-conversion",
+        "-Wno-shadow",
+        "-Wno-shift-sign-overflow",
+        "-Wno-sign-compare",
+        "-Wno-unused-function",
+        "-Wno-unused-member-function",
+        "-Wno-unused-parameter",
+        "-Wno-unused-private-field",
+        "-Wno-unused-template",
+        "-Wno-used-but-marked-unused",
+        "-Wno-zero-as-null-pointer-constant",
+        # gtest depends on this GNU extension being offered.
+        "-Wno-gnu-zero-variadic-macro-arguments",
+    ],
+    "LLVM_EXCEPTIONS_FLAGS": ["-fexceptions"],
+    # /Wall with msvc includes unhelpful warnings such as C4711, C4710, ...
+    "MSVC_FLAGS": [
+        "/W3",
+        "/wd4005",  # macro-redefinition
+        "/wd4068",  # unknown pragma
+        "/wd4180",  # qualifier applied to function type has no meaning; ignored
+        "/wd4244",  # conversion from 'type1' to 'type2', possible loss of data
+        "/wd4267",  # conversion from 'size_t' to 'type', possible loss of data
+        # forcing value to bool 'true' or 'false' (performance warning)
+        "/wd4800",
+        "/DNOMINMAX",  # Don't define min and max macros (windows.h)
+        # Don't bloat namespace with incompatible winsock versions.
+        "/DWIN32_LEAN_AND_MEAN",
+        # Don't warn about usage of insecure C functions.
+        "/D_CRT_SECURE_NO_WARNINGS",
+        "/D_SCL_SECURE_NO_WARNINGS",
+        # Introduced in VS 2017 15.8, allow overaligned types in aligned_storage
+        "/D_ENABLE_EXTENDED_ALIGNED_STORAGE",
+    ],
+    "MSVC_TEST_FLAGS": [
+        "/wd4018",  # signed/unsigned mismatch
+        "/wd4101",  # unreferenced local variable
+        "/wd4503",  # decorated name length exceeded, name was truncated
+    ],
+    "MSVC_EXCEPTIONS_FLAGS": [
+        "/U_HAS_EXCEPTIONS", "/D_HAS_EXCEPTIONS=1", "/EHsc"
+    ]
+}
diff --git a/absl/copts/generate_copts.py b/absl/copts/generate_copts.py
new file mode 100644
index 00000000..5052e22a
--- /dev/null
+++ b/absl/copts/generate_copts.py
@@ -0,0 +1,107 @@
+"""Generate Abseil compile compile option configs.
+
+Usage: python absl/generate_copts.py
+
+The configs are generated from copts.py.
+"""
+
+from os import path
+import sys
+from copts import COPT_VARS
+
+
+# Helper functions
+def file_header_lines():
+  return [
+      "GENERATED! DO NOT MANUALLY EDIT THIS FILE.", "",
+      "(1) Edit absl/copts/copts.py.",
+      "(2) Run `python <path_to_absl>/copts/generate_copts.py`."
+  ]
+
+
+def flatten(*lists):
+  return [item for sublist in lists for item in sublist]
+
+
+def relative_filename(filename):
+  return path.join(path.dirname(__file__), filename)
+
+
+# Style classes.  These contain all the syntactic styling needed to generate a
+# copt file for different build tools.
+class CMakeStyle(object):
+  """Style object for CMake copts file."""
+
+  def separator(self):
+    return ""
+
+  def list_introducer(self, name):
+    return "list(APPEND " + name
+
+  def list_closer(self):
+    return ")\n"
+
+  def docstring(self):
+    return "\n".join((("# " + line).strip() for line in file_header_lines()))
+
+  def filename(self):
+    return "GENERATED_AbseilCopts.cmake"
+
+
+class StarlarkStyle(object):
+  """Style object for Starlark copts file."""
+
+  def separator(self):
+    return ","
+
+  def list_introducer(self, name):
+    return name + " = ["
+
+  def list_closer(self):
+    return "]\n"
+
+  def docstring(self):
+    docstring_quotes = "\"\"\""
+    return docstring_quotes + "\n".join(
+        flatten(file_header_lines(), [docstring_quotes]))
+
+  def filename(self):
+    return "GENERATED_copts.bzl"
+
+
+# Copt file generation
+def copt_list(name, arg_list, style):
+  make_line = lambda s: "    \"" + s + "\"" + style.separator()
+  external_str_list = [make_line(s) for s in arg_list]
+
+  return "\n".join(
+      flatten(
+          [style.list_introducer(name)],
+          external_str_list,
+          [style.list_closer()]))
+
+
+def generate_copt_file(style):
+  """Creates a generated copt file using the given style object.
+
+  Args:
+    style: either StarlarkStyle() or CMakeStyle()
+  """
+  with open(relative_filename(style.filename()), "w") as f:
+    f.write(style.docstring())
+    f.write("\n")
+    for var_name, arg_list in sorted(COPT_VARS.items()):
+      f.write("\n")
+      f.write(copt_list(var_name, arg_list, style))
+
+
+def main(argv):
+  if len(argv) > 1:
+    raise RuntimeError("generate_copts needs no command line args")
+
+  generate_copt_file(StarlarkStyle())
+  generate_copt_file(CMakeStyle())
+
+
+if __name__ == "__main__":
+  main(sys.argv)