5 files changed, 53 insertions, 3 deletions
diff --git a/absl/flags/BUILD.bazel b/absl/flags/BUILD.bazel
index 92bd4f15..62fb9a8b 100644
--- a/absl/flags/BUILD.bazel
+++ b/absl/flags/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "path_util",
@@ -179,6 +179,7 @@ cc_library(
         ":private_handle_accessor",
         "//absl/base:config",
         "//absl/base:core_headers",
+        "//absl/container:flat_hash_map",
         "//absl/strings",
         "//absl/synchronization",
     ],
@@ -464,6 +465,7 @@ cc_test(
         ":flag",
         ":marshalling",
         ":reflection",
+        ":usage_internal",
         "//absl/memory",
         "//absl/strings",
         "@com_google_googletest//:gtest_main",
diff --git a/absl/flags/CMakeLists.txt b/absl/flags/CMakeLists.txt
index 343774de..28bd5a85 100644
--- a/absl/flags/CMakeLists.txt
+++ b/absl/flags/CMakeLists.txt
@@ -165,6 +165,7 @@ absl_cc_library(
     absl::flags_config
     absl::strings
     absl::synchronization
+    absl::flat_hash_map
 )
 
 # Internal-only target, do not depend on directly.
@@ -407,9 +408,10 @@ absl_cc_test(
     absl::flags_commandlineflag_internal
     absl::flags
     absl::flags_reflection
+    absl::flags_usage
     absl::memory
     absl::strings
-    gtest_main
+    gmock_main
 )
 
 absl_cc_test(
diff --git a/absl/flags/reflection.cc b/absl/flags/reflection.cc
index e4145b34..d7060221 100644
--- a/absl/flags/reflection.cc
+++ b/absl/flags/reflection.cc
@@ -303,5 +303,15 @@ CommandLineFlag* FindCommandLineFlag(absl::string_view name) {
   return registry.FindFlagLocked(name);
 }
 
+// --------------------------------------------------------------------
+
+absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> GetAllFlags() {
+  absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> res;
+  flags_internal::ForEachFlag([&](CommandLineFlag& flag) {
+    res.insert({flag.Name(), &flag});
+  });
+  return res;
+}
+
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/reflection.h b/absl/flags/reflection.h
index 045f9784..4ce0ab6c 100644
--- a/absl/flags/reflection.h
+++ b/absl/flags/reflection.h
@@ -26,6 +26,7 @@
 #include <string>
 
 #include "absl/base/config.h"
+#include "absl/container/flat_hash_map.h"
 #include "absl/flags/commandlineflag.h"
 #include "absl/flags/internal/commandlineflag.h"
 
@@ -40,7 +41,11 @@ class FlagSaverImpl;
 // Returns the reflection handle of an Abseil flag of the specified name, or
 // `nullptr` if not found. This function will emit a warning if the name of a
 // 'retired' flag is specified.
-CommandLineFlag* FindCommandLineFlag(absl::string_view name);
+absl::CommandLineFlag* FindCommandLineFlag(absl::string_view name);
+
+// Returns current state of the Flags registry in a form of mapping from flag
+// name to a flag reflection handle.
+absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> GetAllFlags();
 
 //------------------------------------------------------------------------------
 // FlagSaver
diff --git a/absl/flags/reflection_test.cc b/absl/flags/reflection_test.cc
index 2da0a0ec..1a1dcb4a 100644
--- a/absl/flags/reflection_test.cc
+++ b/absl/flags/reflection_test.cc
@@ -18,7 +18,9 @@
 #include <memory>
 #include <string>
 
+#include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include "absl/flags/declare.h"
 #include "absl/flags/flag.h"
 #include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/marshalling.h"
@@ -30,6 +32,8 @@ ABSL_FLAG(int, int_flag, 1, "int_flag help");
 ABSL_FLAG(std::string, string_flag, "dflt", "string_flag help");
 ABSL_RETIRED_FLAG(bool, bool_retired_flag, false, "bool_retired_flag help");
 
+ABSL_DECLARE_FLAG(bool, help);
+
 namespace {
 
 namespace flags = absl::flags_internal;
@@ -61,6 +65,33 @@ TEST_F(ReflectionTest, TestFindCommandLineFlag) {
 
 // --------------------------------------------------------------------
 
+TEST_F(ReflectionTest, TestGetAllFlags) {
+  (void)absl::GetFlag(FLAGS_help);  // Force linking of usage flags.
+
+  auto all_flags = absl::GetAllFlags();
+  EXPECT_NE(all_flags.find("int_flag"), all_flags.end());
+  EXPECT_NE(all_flags.find("bool_retired_flag"), all_flags.end());
+  EXPECT_NE(all_flags.find("help"), all_flags.end());
+  EXPECT_EQ(all_flags.find("some_undefined_flag"), all_flags.end());
+
+  std::vector<absl::string_view> flag_names_first_attempt;
+  auto all_flags_1 = absl::GetAllFlags();
+  for (auto f : all_flags_1) {
+    flag_names_first_attempt.push_back(f.first);
+  }
+
+  std::vector<absl::string_view> flag_names_second_attempt;
+  auto all_flags_2 = absl::GetAllFlags();
+  for (auto f : all_flags_2) {
+    flag_names_second_attempt.push_back(f.first);
+  }
+
+  EXPECT_THAT(flag_names_first_attempt,
+              ::testing::UnorderedElementsAreArray(flag_names_second_attempt));
+}
+
+// --------------------------------------------------------------------
+
 struct CustomUDT {
   CustomUDT() : a(1), b(1) {}
   CustomUDT(int a_, int b_) : a(a_), b(b_) {}