C++: Fix handling of #undef

* If the macro is defined before, track its reference
* Synchronize environment line before calling remove, which
  currently sets incorrect line
* Set macro offset

Task-number: QTCREATORBUG-10454
Change-Id: I480d16423a976a025bb8c71046610a46f9d7b0fd
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/libs/cplusplus/pp-engine.cpp

@@ -1951,10 +1951,19 @@ void Preprocessor::handleUndefDirective(PPToken *tk)
     lex(tk); // consume "undef" token
     if (tk->is(T_IDENTIFIER)) {
         const ByteArrayRef macroName = tk->asByteArrayRef();
-        const Macro *macro = m_env->remove(macroName);
+        const unsigned offset = tk->offset + m_state.m_offsetRef;
+        // Track macro use if previously defined
+        if (m_client) {
+            if (const Macro *existingMacro = m_env->resolve(macroName))
+                m_client->notifyMacroReference(offset, tk->lineno, *existingMacro);
+        }
+        synchronizeOutputLines(*tk);
+        Macro *macro = m_env->remove(macroName);
 
-        if (m_client && macro)
+        if (m_client && macro) {
+            macro->setOffset(offset);
             m_client->macroAdded(*macro);
+        }
         lex(tk); // consume macro name
 #ifndef NO_DEBUG
     } else {

tests/auto/cplusplus/preprocessor/tst_preprocessor.cpp

@@ -374,6 +374,7 @@ private slots:
     void include_guard_data();
     void empty_trailing_lines();
     void empty_trailing_lines_data();
+    void undef();
 };
 
 // Remove all #... lines, and 'simplify' string, to allow easily comparing the result
@@ -1739,6 +1740,46 @@ void tst_Preprocessor::empty_trailing_lines_data()
     );
 }
 
+void tst_Preprocessor::undef()
+{
+    Environment env;
+    QByteArray output;
+    MockClient client(&env, &output);
+    Preprocessor preprocess(&client, &env);
+    QByteArray input =
+            "#define FOO\n"
+            "#define FOO2\n"
+            "#undef FOO\n"
+            "#undef BAR\n";
+    preprocess.run(QLatin1String("<stdin>"), input);
+    QCOMPARE(env.macroCount(), 4U);
+    Macro *macro = env.macroAt(0);
+    QCOMPARE(macro->name(), QByteArray("FOO"));
+    QCOMPARE(macro->offset(), 8U);
+    QCOMPARE(macro->line(), 1U);
+    QVERIFY(!macro->isHidden());
+    macro = env.macroAt(1);
+    QCOMPARE(macro->name(), QByteArray("FOO2"));
+    QCOMPARE(macro->offset(), 20U);
+    QCOMPARE(macro->line(), 2U);
+    QVERIFY(!macro->isHidden());
+    macro = env.macroAt(2);
+    QCOMPARE(macro->name(), QByteArray("FOO"));
+    QCOMPARE(macro->offset(), 32U);
+    QCOMPARE(macro->line(), 3U);
+    QVERIFY(macro->isHidden());
+    macro = env.macroAt(3);
+    QCOMPARE(macro->name(), QByteArray("BAR"));
+    QCOMPARE(macro->offset(), 43U);
+    QCOMPARE(macro->line(), 4U);
+    QVERIFY(macro->isHidden());
+    QList<QByteArray> macros = client.definedMacros();
+    QVERIFY(macros.contains("FOO"));
+    QVERIFY(macros.contains("FOO2"));
+    QCOMPARE(client.macroUsesLine()["FOO"], (QList<unsigned>() << 3U));
+    QVERIFY(client.macroUsesLine()["BAR"].isEmpty());
+}
+
 void tst_Preprocessor::compare_input_output(bool keepComments)
 {
     QFETCH(QByteArray, input);