fixed #12424 - CppCheck: provide a preprocessor object with --clang (fixes assert)

lib/cppcheck.cpp

@@ -499,9 +499,10 @@ unsigned int CppCheck::checkClang(const std::string &path)
     }
 
     try {
-        std::istringstream ast(output2);
-        Tokenizer tokenizer(mSettings, this);
+        Preprocessor preprocessor(mSettings, this);
+        Tokenizer tokenizer(mSettings, this, &preprocessor);
         tokenizer.list.appendFileIfNew(path);
+        std::istringstream ast(output2);
         clangimport::parseClangAstDump(tokenizer, ast);
         ValueFlow::setValues(tokenizer.list,
                              const_cast<SymbolDatabase&>(*tokenizer.getSymbolDatabase()),

test/cli/clang-import_test.py

@@ -139,4 +139,15 @@ def test_log(tmpdir):
         'Checking {} ...'.format(test_file).replace('\\', '/'),
     ]
 
-    assert_cppcheck(args, ec_exp=0, err_exp=[], out_exp=out_lines)
+    assert_cppcheck(args, ec_exp=0, err_exp=[], out_exp=out_lines)
+
+
+def test_warning(tmpdir):  # #12424
+    test_file = os.path.join(tmpdir, 'test_2')
+    with open(test_file, 'wt') as f:
+        f.write('''void f() {}''')
+
+    exitcode, stdout, stderr = cppcheck(['-q', '--enable=warning', '--clang', test_file])
+    assert exitcode == 0, stderr # do not assert
+    assert stdout == ''
+    assert stderr == ''