Changes imported from Abseil "staging" branch:

- e4999febdfea4d392284bfbc9dce9520b26d98cb Remove an erronous __attribute__((...)) tag. by Abseil Team <absl-team@google.com>
  - 61db01b3eaad3563aa2f97d41799ef1339d57c04 Remove the default parameter value from overridden overfl... by Abseil Team <absl-team@google.com>
  - e7dc1ee6bb523b2173915e1978f7e3831f5484f6 Fix the include guards for exception_safety_testing.h by Jon Cohen <cohenjon@google.com>

GitOrigin-RevId: e4999febdfea4d392284bfbc9dce9520b26d98cb
Change-Id: I7837e125138a1e623d9b6394c0ea5f624b904ea2

absl/base/internal/exception_safety_testing.h

@@ -1,7 +1,7 @@
 // Utilities for testing exception-safety
 
-#ifndef ABSL_BASE_INTERNAL_EXCEPTION_TESTING_H_
-#define ABSL_BASE_INTERNAL_EXCEPTION_TESTING_H_
+#ifndef ABSL_BASE_INTERNAL_EXCEPTION_SAFETY_TESTING_H_
+#define ABSL_BASE_INTERNAL_EXCEPTION_SAFETY_TESTING_H_
 
 #include <cstddef>
 #include <cstdint>

absl/base/thread_annotations.h

@@ -52,7 +52,7 @@
 //   Mutex mu;
 //   int p1 GUARDED_BY(mu);
 #define GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(guarded_by(x))
-#define GUARDED_VAR   THREAD_ANNOTATION_ATTRIBUTE__(guarded)
+#define GUARDED_VAR  // no-op
 
 // PT_GUARDED_BY()
 //
@@ -72,7 +72,7 @@
 //     // guarded by `mu2`:
 //     int *q GUARDED_BY(mu1) PT_GUARDED_BY(mu2);
 #define PT_GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_by(x))
-#define PT_GUARDED_VAR   THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded)
+#define PT_GUARDED_VAR  // no-op
 
 // ACQUIRED_AFTER() / ACQUIRED_BEFORE()
 //

absl/strings/internal/ostringstream.h

@@ -75,7 +75,7 @@ class OStringStream : private std::basic_streambuf<char>, public std::ostream {
  private:
   using Buf = std::basic_streambuf<char>;
 
-  Buf::int_type overflow(int c = Buf::traits_type::eof()) override {
+  Buf::int_type overflow(int c) override {
     assert(s_);
     if (!Buf::traits_type::eq_int_type(c, Buf::traits_type::eof()))
       s_->push_back(static_cast<char>(c));