Prints help when encountering unrecognized Google Test flags.

include/gtest/internal/gtest-port.h

@@ -169,6 +169,7 @@
 
 #define GTEST_DEV_EMAIL_ "googletestframework@@googlegroups.com"
 #define GTEST_FLAG_PREFIX_ "gtest_"
+#define GTEST_FLAG_PREFIX_DASH_ "gtest-"
 #define GTEST_FLAG_PREFIX_UPPER_ "GTEST_"
 #define GTEST_NAME_ "Google Test"
 #define GTEST_PROJECT_URL_ "http://code.google.com/p/googletest/"

src/gtest.cc

@@ -4444,6 +4444,33 @@ bool ParseStringFlag(const char* str, const char* flag, String* value) {
   return true;
 }
 
+// Determines whether a string pointed by *str has the prefix parameter as
+// its prefix and advances it to point past the prefix if it does.
+bool SkipPrefix(const char* prefix, const char** str) {
+  const int prefix_len = strlen(prefix);
+
+  if (strncmp(*str, prefix, prefix_len) != 0)
+    return false;
+
+  *str += prefix_len;
+  return true;
+}
+
+// Determines whether a string has a prefix that Google Test uses for its
+// flags, i.e., starts with GTEST_FLAG_PREFIX_ or GTEST_FLAG_PREFIX_DASH_.
+// If Google Test detects that a command line flag has its prefix but is not
+// recognized, it will print its help message. Flags starting with
+// GTEST_INTERNAL_PREFIX_ followed by "internal_" are considered Google Test
+// internal flags and do not trigger the help message.
+bool HasGoogleTestFlagPrefix(const char* str) {
+  return (SkipPrefix("--", &str) ||
+          SkipPrefix("-", &str) ||
+          SkipPrefix("/", &str)) &&
+         !SkipPrefix(GTEST_FLAG_PREFIX_ "internal_", &str) &&
+         (SkipPrefix(GTEST_FLAG_PREFIX_, &str) ||
+          SkipPrefix(GTEST_FLAG_PREFIX_DASH_, &str));
+}
+
 // Prints a string containing code-encoded text.  The following escape
 // sequences can be used in the string to control the text color:
 //
@@ -4601,7 +4628,10 @@ void ParseGoogleTestFlagsOnlyImpl(int* argc, CharType** argv) {
       // an element.
       i--;
     } else if (arg_string == "--help" || arg_string == "-h" ||
-               arg_string == "-?" || arg_string == "/?") {
+               arg_string == "-?" || arg_string == "/?" ||
+               HasGoogleTestFlagPrefix(arg)) {
+      // Both help flag and unrecognized Google Test flags (excluding
+      // internal ones) trigger help display.
       g_help_flag = true;
     }
   }

test/gtest_help_test.py

@@ -50,6 +50,11 @@ PROGRAM_PATH = gtest_test_utils.GetTestExecutablePath('gtest_help_test_')
 FLAG_PREFIX = '--gtest_'
 CATCH_EXCEPTIONS_FLAG = FLAG_PREFIX + 'catch_exceptions'
 DEATH_TEST_STYLE_FLAG = FLAG_PREFIX + 'death_test_style'
+UNKNOWN_FLAG = FLAG_PREFIX + 'unknown_flag_for_testing'
+INCORRECT_FLAG_VARIANTS = [re.sub('^--', '-', DEATH_TEST_STYLE_FLAG),
+                           re.sub('^--', '/', DEATH_TEST_STYLE_FLAG),
+                           re.sub('_', '-', DEATH_TEST_STYLE_FLAG)]
+INTERNAL_FLAG_FOR_TESTING = FLAG_PREFIX + 'internal_flag_for_testing'
 
 # The help message must match this regex.
 HELP_REGEX = re.compile(
@@ -88,8 +93,14 @@ class GTestHelpTest(gtest_test_utils.TestCase):
   """Tests the --help flag and its equivalent forms."""
 
   def TestHelpFlag(self, flag):
-    """Verifies that the right message is printed and the tests are
-    skipped when the given flag is specified."""
+    """Verifies correct behavior when help flag is specified.
+
+    The right message must be printed and the tests must
+    skipped when the given flag is specified.
+
+    Args:
+      flag:  A flag to pass to the binary or None.
+    """
 
     exit_code, output = RunWithFlag(flag)
     self.assertEquals(0, exit_code)
@@ -101,6 +112,20 @@ class GTestHelpTest(gtest_test_utils.TestCase):
       self.assert_(CATCH_EXCEPTIONS_FLAG not in output, output)
       self.assert_(DEATH_TEST_STYLE_FLAG in output, output)
 
+  def TestNonHelpFlag(self, flag):
+    """Verifies correct behavior when no help flag is specified.
+
+    Verifies that when no help flag is specified, the tests are run
+    and the help message is not printed.
+
+    Args:
+      flag:  A flag to pass to the binary or None.
+    """
+
+    exit_code, output = RunWithFlag(flag)
+    self.assert_(exit_code != 0)
+    self.assert_(not HELP_REGEX.search(output), output)
+
   def testPrintsHelpWithFullFlag(self):
     self.TestHelpFlag('--help')
 
@@ -113,13 +138,24 @@ class GTestHelpTest(gtest_test_utils.TestCase):
   def testPrintsHelpWithWindowsStyleQuestionFlag(self):
     self.TestHelpFlag('/?')
 
+  def testPrintsHelpWithUnrecognizedGoogleTestFlag(self):
+    self.TestHelpFlag(UNKNOWN_FLAG)
+
+  def testPrintsHelpWithIncorrectFlagStyle(self):
+    for incorrect_flag in INCORRECT_FLAG_VARIANTS:
+      self.TestHelpFlag(incorrect_flag)
+
   def testRunsTestsWithoutHelpFlag(self):
     """Verifies that when no help flag is specified, the tests are run
     and the help message is not printed."""
 
-    exit_code, output = RunWithFlag(None)
-    self.assert_(exit_code != 0)
-    self.assert_(not HELP_REGEX.search(output), output)
+    self.TestNonHelpFlag(None)
+
+  def testRunsTestsWithGtestInternalFlag(self):
+    """Verifies that the tests are run and no help message is printed when
+    a flag starting with Google Test prefix and 'internal_' is supplied."""
+
+    self.TestNonHelpFlag(INTERNAL_FLAG_FOR_TESTING)
 
 
 if __name__ == '__main__':