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..5671626060fa6d6ac172dea3758196c4ca1a0371 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 +266,27 @@ 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;
+  void (*fp1)() = DcheckEmptyFunction1;
+  void (*fp2)() = DcheckEmptyFunction2;
+  void (*fp3)() = DcheckEmptyFunction1;
+  DCHECK_EQ(fp1, fp3);
+  EXPECT_EQ(DCHECK_IS_ON() ? 0 : 0, log_sink_call_count);

[Nico, 2016/11/23 18:21:10]

Err, replace `DCHECK_IS_ON() ? 0 : 0` with `0`? :-)

[Raphael Kubo da Costa (rakuco), 2016/11/23 18:58:09]

Brain fart :(

+  DCHECK_EQ(fp1, fp2);
+  EXPECT_EQ(DCHECK_IS_ON() ? 1 : 0, log_sink_call_count);
+  struct MemberFunctions {
+    static void MemberFunction1(){};

[Nico, 2016/11/23 18:21:10]

Actually, this isn't a member function, this is a regular function since it's
static. I think you want:
  struct MemberFunctions {
    void MemberFunction1() {}
    void MemberFunction2() {}
  };
  void (MemberFunctions::* mp1)() = &MemberFunctions::MemberFunction1;
  void (MemberFunctions::* mp2)() = &MemberFunctions::MemberFunction2;
  DCHECK_EQ(fp1, &MemberFunctions::MemberFunction1);
  DCHECK_EQ(fp2, &MemberFunctions::MemberFunction1);

Also, I'd move the first of these checks (and the whole struct decl) up so that
you can EXPECT_EQ(0, log_sink_call_count) after the first DCHECK

[Raphael Kubo da Costa (rakuco), 2016/11/23 18:58:09]

That works too; the reason I went for static functions is that I only started
working on it because wtf's ArrayBufferContents does

    DCHECK_EQ(s_adjustAmountOfExternalAllocatedMemoryFunction,
              defaultAdjustAmountOfExternalAllocatedMemoryFunction);

Having a static variable will require me to move the struct declaration out of
the function, so I guess I'll just go with actual member functions.

+    static void TestDCHECK() {
+      void (*fp)() = MemberFunction1;
+      DCHECK_EQ(fp, MemberFunction1);
+      EXPECT_EQ(DCHECK_IS_ON() ? 1 : 0, log_sink_call_count);
+      DCHECK_EQ(fp, TestDCHECK);
+      EXPECT_EQ(DCHECK_IS_ON() ? 2 : 0, log_sink_call_count);
+    }
+  };
+  MemberFunctions::TestDCHECK();
 }
 
 TEST_F(LoggingTest, DcheckReleaseBehavior) {