C++: Preserve comments after preprocessor directives

Task-number: QTCREATORBUG-11216
Change-Id: Iac10e75f0f5c504b79e8466607dc1f478e578f99
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/libs/cplusplus/pp-engine.cpp

@@ -898,6 +898,11 @@ void Preprocessor::skipPreprocesorDirective(PPToken *tk)
     ScopedBoolSwap s(m_state.m_inPreprocessorDirective, true);
 
     while (isContinuationToken(*tk)) {
+        if (tk->isComment()) {
+            synchronizeOutputLines(*tk);
+            enforceSpacing(*tk, true);
+            currentOutputBuffer().append(tk->tokenStart(), tk->length());
+        }
         lex(tk);
     }
 }
@@ -1703,8 +1708,13 @@ void Preprocessor::handleDefineDirective(PPToken *tk)
         previousLine = tk->lineno;
 
         // Discard comments in macro definitions (keep comments flag doesn't apply here).
-        if (!tk->isComment())
+        if (tk->isComment()) {
+            synchronizeOutputLines(*tk);
+            enforceSpacing(*tk, true);
+            currentOutputBuffer().append(tk->tokenStart(), tk->length());
+        } else {
             bodyTokens.push_back(*tk);
+        }
 
         lex(tk);
     }

tests/auto/cplusplus/preprocessor/tst_preprocessor.cpp

@@ -1357,7 +1357,7 @@ void tst_Preprocessor::comments_within_data()
             "}\n"
         ) << _(
             "# 1 \"<stdin>\"\n"
-            "\n"
+            "              //comment\n"
             "\n"
             "void foo() {\n"
             "    if (\n"
@@ -1368,6 +1368,75 @@ void tst_Preprocessor::comments_within_data()
             "           ) {}\n"
             "}\n"
     );
+    QTest::newRow("case 8") << _(
+            "#define FOO /* comment */ 0\n"
+            "FOO\n"
+        ) << _(
+            "# 1 \"<stdin>\"\n"
+            "\n"
+            "# expansion begin 28,3 ~1\n"
+            "0\n"
+            "# expansion end\n"
+            "# 3 \"<stdin>\"\n"
+        ) << _(
+            "# 1 \"<stdin>\"\n"
+            "            /* comment */\n"
+            "# expansion begin 28,3 ~1\n"
+            "0\n"
+            "# expansion end\n"
+            "# 3 \"<stdin>\"\n"
+    );
+
+    QTest::newRow("case 9") << _(
+            "#define FOO /* comment1 */ /* comment2 */ 0\n"
+            "FOO\n"
+        ) << _(
+            "# 1 \"<stdin>\"\n"
+            "\n"
+            "# expansion begin 44,3 ~1\n"
+            "0\n"
+            "# expansion end\n"
+            "# 3 \"<stdin>\"\n"
+        ) << _(
+            "# 1 \"<stdin>\"\n"
+            "            /* comment1 */ /* comment2 */\n"
+            "# expansion begin 44,3 ~1\n"
+            "0\n"
+            "# expansion end\n"
+            "# 3 \"<stdin>\"\n"
+    );
+
+    QTest::newRow("case 10") << _(
+            "#define FOO /* comment1 */   /* comment2 */ 0 /* comment3\n"
+            "comment4 */\n"
+            "FOO\n"
+        ) << _(
+            "# 1 \"<stdin>\"\n"
+            "\n"
+            "\n"
+            "# expansion begin 70,3 ~1\n"
+            "0\n"
+            "# expansion end\n"
+            "# 4 \"<stdin>\"\n"
+        ) << _(
+            "# 1 \"<stdin>\"\n"
+            "            /* comment1 */ /* comment2 */ /* comment3\n"
+            "comment4 */\n"
+            "# expansion begin 70,3 ~1\n"
+            "0\n"
+            "# expansion end\n"
+            "# 4 \"<stdin>\"\n"
+    );
+
+    QTest::newRow("case 11") << _(
+            "#include <foo.h> // comment\n"
+        ) << _(
+            "# 1 \"<stdin>\"\n"
+            "\n"
+        ) << _(
+            "# 1 \"<stdin>\"\n"
+            "                 // comment\n"
+    );
 
     QTest::newRow("joined") << _(
             "// comment \\\n"