logging: Provide a specific MakeCheckOpValueString overload for functions

base/logging_unittest.cc

Index: base/logging_unittest.cc
diff --git a/base/logging_unittest.cc b/base/logging_unittest.cc
index 8a20c54fb4c605734bf45c4b8bb582a76276e104..f41cce2f43b390fa9603a14f3f689fe87d0dcb33 100644
--- a/base/logging_unittest.cc
+++ b/base/logging_unittest.cc
@@ -217,6 +217,14 @@ TEST_F(LoggingTest, DcheckStreamsAreLazy) {
 #endif
 }
 
+void DcheckEmptyFunction1() {
+  // Provide a body so that Release builds do not cause the compiler to
+  // optimize DcheckEmptyFunction1 and DcheckEmptyFunction2 as a single
+  // function, which breaks the Dcheck tests below.
+  LOG(INFO) << "DcheckEmptyFunction1";
+}
+void DcheckEmptyFunction2() {}
+
 TEST_F(LoggingTest, Dcheck) {
 #if defined(NDEBUG) && !defined(DCHECK_ALWAYS_ON)
   // Release build.
@@ -258,6 +266,31 @@ TEST_F(LoggingTest, Dcheck) {
   EXPECT_EQ(0, log_sink_call_count);
   DCHECK_EQ(Animal::DOG, Animal::CAT);
   EXPECT_EQ(DCHECK_IS_ON() ? 1 : 0, log_sink_call_count);
+
+  // Test DCHECK on functions and function pointers.
+  log_sink_call_count = 0;
+  struct MemberFunctions {
+    void MemberFunction1() {
+      // See the comment in DcheckEmptyFunction1().
+      LOG(INFO) << "Do not merge with MemberFunction2.";
+    }
+    void MemberFunction2() {}
+  };
+  void (MemberFunctions::*mp1)() = &MemberFunctions::MemberFunction1;
+  void (MemberFunctions::*mp2)() = &MemberFunctions::MemberFunction2;
+  void (*fp1)() = DcheckEmptyFunction1;
+  void (*fp2)() = DcheckEmptyFunction2;
+  void (*fp3)() = DcheckEmptyFunction1;
+  DCHECK_EQ(fp1, fp3);
+  EXPECT_EQ(0, log_sink_call_count);
+  DCHECK_EQ(mp1, &MemberFunctions::MemberFunction1);
+  EXPECT_EQ(0, log_sink_call_count);
+  DCHECK_EQ(mp2, &MemberFunctions::MemberFunction2);
+  EXPECT_EQ(0, log_sink_call_count);
+  DCHECK_EQ(fp1, fp2);
+  EXPECT_EQ(DCHECK_IS_ON() ? 1 : 0, log_sink_call_count);
+  DCHECK_EQ(mp2, &MemberFunctions::MemberFunction1);
+  EXPECT_EQ(DCHECK_IS_ON() ? 2 : 0, log_sink_call_count);
 }
 
 TEST_F(LoggingTest, DcheckReleaseBehavior) {