Export of internal Abseil changes

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5b9d5ce21074c0541432555d383d1b9c5898b553 by Gennadiy Rozental <rogeeff@google.com>:

Convert FlagSaver into public API

PiperOrigin-RevId: 314799739

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5f796c9862b1177f161f4b10fe1a84698ebbb5cf by Abseil Team <absl-team@google.com>:

Google-internal changes only.

PiperOrigin-RevId: 314786474

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67f2ae0ac5ae73bcd9d57a058ac4fea8fc1243ba by Gennadiy Rozental <rogeeff@google.com>:

Makes sure stacktrace_generic is only used with glibc.

Fixes #701

PiperOrigin-RevId: 314726944

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efb1ef3636b0698b79d3ee3590f12c4dff32a3cb by Samuel Benzaquen <sbenza@google.com>:

Take the bits into account when reserving the space for the operation, not just
the exponent.

PiperOrigin-RevId: 314622744
GitOrigin-RevId: 5b9d5ce21074c0541432555d383d1b9c5898b553
Change-Id: I080a5e333e2dc1545b5aa0417882f7ac7116a20c

1 files changed, 38 insertions, 0 deletions

diff --git a/absl/flags/reflection.h b/absl/flags/reflection.h
index e8e24f68..045f9784 100644
--- a/absl/flags/reflection.h
+++ b/absl/flags/reflection.h
@@ -31,6 +31,9 @@
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+class FlagSaverImpl;
+}  // namespace flags_internal
 
 // FindCommandLineFlag()
 //
@@ -39,6 +42,41 @@ ABSL_NAMESPACE_BEGIN
 // 'retired' flag is specified.
 CommandLineFlag* FindCommandLineFlag(absl::string_view name);
 
+//------------------------------------------------------------------------------
+// FlagSaver
+//------------------------------------------------------------------------------
+//
+// A FlagSaver object stores the state of flags in the scope where the FlagSaver
+// is defined, allowing modification of those flags within that scope and
+// automatic restoration of the flags to their previous state upon leaving the
+// scope.
+//
+// A FlagSaver can be used within tests to temporarily change the test
+// environment and restore the test case to its previous state.
+//
+// Example:
+//
+//   void MyFunc() {
+//    absl::FlagSaver fs;
+//    ...
+//    absl::SetFlag(FLAGS_myFlag, otherValue);
+//    ...
+//  } // scope of FlagSaver left, flags return to previous state
+//
+// This class is thread-safe.
+
+class FlagSaver {
+ public:
+  FlagSaver();
+  ~FlagSaver();
+
+  FlagSaver(const FlagSaver&) = delete;
+  void operator=(const FlagSaver&) = delete;
+
+ private:
+  flags_internal::FlagSaverImpl* impl_;
+};
+
 //-----------------------------------------------------------------------------
 
 ABSL_NAMESPACE_END