Check the argument count before indexing config comment log args

A '# do:log.add_output=debug' line read args[1] past the end of the vector.

test/src/test_setup.cc

@@ -0,0 +1,78 @@
+#include "config.h"
+
+#include "test/src/test_setup.h"
+
+#include <fstream>
+#include <string>
+#include <unistd.h>
+#include <torrent/exceptions.h>
+
+#include "setup.h"
+
+CPPUNIT_TEST_SUITE_REGISTRATION(TestSetup);
+
+// Linking setup.o pulls in the help printer, which lives in src/main.cc.
+void
+print_help() {}
+
+namespace {
+
+class temp_config_file {
+public:
+  temp_config_file(const std::string& contents) {
+    char path[] = "/tmp/rtorrent_test_setup_XXXXXX";
+
+    CPPUNIT_ASSERT(::mkstemp(path) != -1);
+    m_path = path;
+
+    std::ofstream file(m_path);
+    file << contents << '\n';
+  }
+
+  ~temp_config_file() { ::unlink(m_path.c_str()); }
+
+  const std::string& path() const { return m_path; }
+
+private:
+  std::string m_path;
+};
+
+// The group name must be a valid one, else option_find_string throws before
+// the output argument is ever touched.
+void
+assert_arg_count_error(const std::string& line) {
+  temp_config_file file(line);
+
+  try {
+    parse_config_file_comments(file.path());
+  } catch (torrent::input_error& e) {
+    CPPUNIT_ASSERT_EQUAL(std::string("Invalid number of arguments."), std::string(e.what()));
+    return;
+  }
+
+  CPPUNIT_FAIL("no torrent::input_error thrown for: " + line);
+}
+
+} // namespace
+
+void
+TestSetup::test_config_comment_log_add_output() {
+  temp_config_file file("# do:log.add_output=debug,test_output");
+
+  CPPUNIT_ASSERT_NO_THROW(parse_config_file_comments(file.path()));
+}
+
+void
+TestSetup::test_config_comment_log_add_output_no_args() {
+  assert_arg_count_error("# do:log.add_output=");
+}
+
+void
+TestSetup::test_config_comment_log_add_output_one_arg() {
+  assert_arg_count_error("# do:log.add_output=debug");
+}
+
+void
+TestSetup::test_config_comment_log_add_output_too_many_args() {
+  assert_arg_count_error("# do:log.add_output=debug,test_output,extra");
+}

test/src/test_setup.h

@@ -0,0 +1,18 @@
+#include "test/helpers/test_fixture.h"
+
+class TestSetup : public test_fixture {
+  CPPUNIT_TEST_SUITE(TestSetup);
+
+  CPPUNIT_TEST(test_config_comment_log_add_output);
+  CPPUNIT_TEST(test_config_comment_log_add_output_no_args);
+  CPPUNIT_TEST(test_config_comment_log_add_output_one_arg);
+  CPPUNIT_TEST(test_config_comment_log_add_output_too_many_args);
+
+  CPPUNIT_TEST_SUITE_END();
+
+public:
+  void test_config_comment_log_add_output();
+  void test_config_comment_log_add_output_no_args();
+  void test_config_comment_log_add_output_one_arg();
+  void test_config_comment_log_add_output_too_many_args();
+};