[trac613] canceled the workaround change for 'selfassignment' in tests.

exclude these warnings in the suppress list instead.
also added some comments about the suppress list.

src/cppcheck-suppress.lst

@@ -1,5 +1,14 @@
+// On some systems cppcheck produces false alarms about 'missing includes'.
+// the following two will suppress, depending on the cppcheck version
+debug
+missingInclude
+// This is a template, and should be excluded from the check
 unreadVariable:src/lib/dns/rdata/template.cc:59
+// These two trigger warnings due to the incomplete implementation.  This is
+// our problem, but we need to suppress the warnings for now.
 functionConst:src/lib/cache/message_cache.h
 functionConst:src/lib/cache/rrset_cache.h
-debug
-missingInclude
+// Intentional self assignment tests.  Suppress warning about them.
+selfAssignment:src/lib/dns/tests/name_unittest.cc:292
+selfAssignment:src/lib/dns/tests/rdata_unittest.cc:227
+selfAssignment:src/lib/dns/tests/tsigkey_unittest.cc:104

src/lib/dns/tests/name_unittest.cc

@@ -288,10 +288,9 @@ TEST_F(NameTest, assignment) {
     delete copy2;
     EXPECT_EQ(copy3, example_name);
 
-    // Self assignment (via a reference to silence cppcheck)
-    Name& copyref(copy);
-    copyref = copy;
-    EXPECT_EQ(example_name, copyref);
+    // Self assignment
+    copy = copy;
+    EXPECT_EQ(example_name, copy);
 }
 
 TEST_F(NameTest, toText) {

src/lib/dns/tests/rdata_unittest.cc

@@ -223,10 +223,9 @@ TEST_F(Rdata_Unknown_Test, assignment) {
     delete copy2;
     EXPECT_EQ(0, copy3.compare(rdata_unknown));
 
-    // Self assignment (via a reference to silence cppcheck)
-    generic::Generic& copyref(copy);
-    copyref = copy;
-    EXPECT_EQ(0, copyref.compare(rdata_unknown));
+    // Self assignment
+    copy = copy;
+    EXPECT_EQ(0, copy.compare(rdata_unknown));
 }
 
 TEST_F(Rdata_Unknown_Test, toText) {

src/lib/dns/tests/tsigkey_unittest.cc

@@ -100,10 +100,9 @@ TEST_F(TSIGKeyTest, assignment) {
     delete copy2;
     compareTSIGKeys(original, copy3);
 
-    // self assignment (via a reference to silence cppcheck)
-    TSIGKey& copyref(copy);
-    copyref = copy;
-    compareTSIGKeys(original, copyref);
+    // self assignment
+    copy = copy;
+    compareTSIGKeys(original, copy);
 }
 
 class TSIGKeyRingTest : public ::testing::Test {