De-pointerize LogStreamer::stream_, and fix move ctor/assign preservation of flags and other stream properties.

PiperOrigin-RevId: 475643360
Change-Id: I061c167da8e45f79c2487f172190adb0177a6c10

4 files changed, 42 insertions, 41 deletions

diff --git a/absl/log/BUILD.bazel b/absl/log/BUILD.bazel
index 45208bd1..2b272ff8 100644
--- a/absl/log/BUILD.bazel
+++ b/absl/log/BUILD.bazel
@@ -169,9 +169,10 @@ cc_library(
         ":log",
         "//absl/base:config",
         "//absl/base:log_severity",
-        "//absl/memory",
         "//absl/strings",
         "//absl/strings:internal",
+        "//absl/types:optional",
+        "//absl/utility",
     ],
 )
 
diff --git a/absl/log/CMakeLists.txt b/absl/log/CMakeLists.txt
index a803ca8f..20f1b686 100644
--- a/absl/log/CMakeLists.txt
+++ b/absl/log/CMakeLists.txt
@@ -506,9 +506,10 @@ absl_cc_library(
     absl::config
     absl::log
     absl::log_severity
-    absl::memory
+    absl::optional
     absl::strings
     absl::strings_internal
+    absl::utility
   PUBLIC
 )
 
diff --git a/absl/log/log_streamer.h b/absl/log/log_streamer.h
index c3776cec..20327455 100644
--- a/absl/log/log_streamer.h
+++ b/absl/log/log_streamer.h
@@ -31,9 +31,10 @@
 #include "absl/base/config.h"
 #include "absl/base/log_severity.h"
 #include "absl/log/log.h"
-#include "absl/memory/memory.h"
 #include "absl/strings/internal/ostringstream.h"
 #include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "absl/utility/utility.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -81,8 +82,7 @@ class LogStreamer final {
       : severity_(severity),
         line_(line),
         file_(file),
-        stream_(
-            absl::make_unique<absl::strings_internal::OStringStream>(&buf_)) {
+        stream_(absl::in_place, &buf_) {
     // To match `LOG`'s defaults:
     stream_->setf(std::ios_base::showbase | std::ios_base::boolalpha);
   }
@@ -94,10 +94,8 @@ class LogStreamer final {
         line_(that.line_),
         file_(std::move(that.file_)),
         buf_(std::move(that.buf_)),
-        stream_(that.stream_
-                    ? absl::make_unique<absl::strings_internal::OStringStream>(
-                          &buf_)
-                    : nullptr) {
+        stream_(std::move(that.stream_)) {
+    if (stream_.has_value()) stream_->str(&buf_);
     that.stream_.reset();
   }
   LogStreamer& operator=(LogStreamer&& that) {
@@ -106,10 +104,8 @@ class LogStreamer final {
     file_ = std::move(that.file_);
     line_ = that.line_;
     buf_ = std::move(that.buf_);
-    stream_ =
-        that.stream_
-            ? absl::make_unique<absl::strings_internal::OStringStream>(&buf_)
-            : nullptr;
+    stream_ = std::move(that.stream_);
+    if (stream_.has_value()) stream_->str(&buf_);
     that.stream_.reset();
     return *this;
   }
@@ -118,7 +114,8 @@ class LogStreamer final {
   //
   // Logs this LogStreamer's buffered content as if by LOG.
   ~LogStreamer() {
-    LOG_IF(LEVEL(severity_), stream_).AtLocation(file_, line_) << buf_;
+    LOG_IF(LEVEL(severity_), stream_.has_value()).AtLocation(file_, line_)
+        << buf_;
   }
 
   // LogStreamer::stream()
@@ -132,11 +129,9 @@ class LogStreamer final {
   int line_;
   std::string file_;
   std::string buf_;
-  // TODO(durandal): de-pointerize this once we are off of our old mostly-C++11
-  // libstdc++ (which lacks move constructors for std streams).
-  // `stream_` is null in a moved-from `LogStreamer`; this is in fact how we
-  // recognize one to avoid logging when it is destroyed or reassigned.
-  std::unique_ptr<absl::strings_internal::OStringStream> stream_;
+  // A disengaged `stream_` indicates a moved-from `LogStreamer` that should not
+  // `LOG` upon destruction.
+  absl::optional<absl::strings_internal::OStringStream> stream_;
 };
 
 // LogInfoStreamer()
diff --git a/absl/log/log_streamer_test.cc b/absl/log/log_streamer_test.cc
index d7beb5bc..328d70d0 100644
--- a/absl/log/log_streamer_test.cc
+++ b/absl/log/log_streamer_test.cc
@@ -15,6 +15,7 @@
 
 #include "absl/log/log_streamer.h"
 
+#include <ios>
 #include <iostream>
 #include <utility>
 
@@ -300,48 +301,51 @@ TEST(LogStreamerTest, MoveConstruction) {
 
   EXPECT_CALL(
       test_sink,
-      Send(AllOf(
-          SourceFilename(Eq("path/file.cc")), SourceLine(Eq(1234)),
-          LogSeverity(Eq(absl::LogSeverity::kInfo)),
-          TextMessage(Eq("hello world")),
-          ENCODED_MESSAGE(EqualsProto(R"pb(value { str: "hello world" })pb")),
-          Stacktrace(IsEmpty()))));
+      Send(AllOf(SourceFilename(Eq("path/file.cc")), SourceLine(Eq(1234)),
+                 LogSeverity(Eq(absl::LogSeverity::kInfo)),
+                 TextMessage(Eq("hello 0x10 world 0x10")),
+                 ENCODED_MESSAGE(EqualsProto(R"pb(value {
+                                                    str: "hello 0x10 world 0x10"
+                                                  })pb")),
+                 Stacktrace(IsEmpty()))));
 
   test_sink.StartCapturingLogs();
   auto streamer1 = absl::LogInfoStreamer("path/file.cc", 1234);
-  streamer1.stream() << "hello";
+  streamer1.stream() << "hello " << std::hex << 16;
   absl::LogStreamer streamer2(std::move(streamer1));
-  streamer2.stream() << " world";
+  streamer2.stream() << " world " << 16;
 }
 
 TEST(LogStreamerTest, MoveAssignment) {
   absl::ScopedMockLog test_sink(absl::MockLogDefault::kDisallowUnexpected);
 
+  testing::InSequence seq;
   EXPECT_CALL(
       test_sink,
-      Send(AllOf(SourceFilename(Eq("path/file.cc")), SourceLine(Eq(1234)),
-                 LogSeverity(Eq(absl::LogSeverity::kInfo)),
-                 TextMessage(Eq("hello")),
-                 ENCODED_MESSAGE(EqualsProto(R"pb(value { str: "hello" })pb")),
+      Send(AllOf(SourceFilename(Eq("path/file2.cc")), SourceLine(Eq(5678)),
+                 LogSeverity(Eq(absl::LogSeverity::kWarning)),
+                 TextMessage(Eq("something else")),
+                 ENCODED_MESSAGE(EqualsProto(R"pb(value {
+                                                    str: "something else"
+                                                  })pb")),
                  Stacktrace(IsEmpty()))));
-
   EXPECT_CALL(
       test_sink,
-      Send(AllOf(SourceFilename(Eq("elsewhere/name.cc")), SourceLine(Eq(5678)),
-                 LogSeverity(Eq(absl::LogSeverity::kWarning)),
-                 TextMessage(Eq("world; goodbye")),
+      Send(AllOf(SourceFilename(Eq("path/file.cc")), SourceLine(Eq(1234)),
+                 LogSeverity(Eq(absl::LogSeverity::kInfo)),
+                 TextMessage(Eq("hello 0x10 world 0x10")),
                  ENCODED_MESSAGE(EqualsProto(R"pb(value {
-                                                    str: "world; goodbye"
+                                                    str: "hello 0x10 world 0x10"
                                                   })pb")),
                  Stacktrace(IsEmpty()))));
 
   test_sink.StartCapturingLogs();
   auto streamer1 = absl::LogInfoStreamer("path/file.cc", 1234);
-  streamer1.stream() << "hello";
-  auto streamer2 = absl::LogWarningStreamer("elsewhere/name.cc", 5678);
-  streamer2.stream() << "world";
-  streamer1 = std::move(streamer2);
-  streamer1.stream() << "; goodbye";
+  streamer1.stream() << "hello " << std::hex << 16;
+  auto streamer2 = absl::LogWarningStreamer("path/file2.cc", 5678);
+  streamer2.stream() << "something else";
+  streamer2 = std::move(streamer1);
+  streamer2.stream() << " world " << 16;
 }
 
 TEST(LogStreamerTest, CorrectDefaultFlags) {