Add parameter-less InitLogging().

Also document that this function should only be called from a
single thread.

vtkm/cont/Logging.cxx

@@ -129,6 +129,14 @@ void InitLogging(int& argc, char* argv[])
 #endif // VTKM_ENABLE_LOGGING
 }
 
+void InitLogging()
+{
+  int argc = 1;
+  char dummy[1] = { '\0' };
+  char* argv[2] = { dummy, nullptr };
+  InitLogging(argc, argv);
+}
+
 VTKM_CONT
 void SetStderrLogLevel(LogLevel level)
 {

vtkm/cont/Logging.h

@@ -321,10 +321,21 @@ enum class LogLevel
  * Initializes logging. Sets up custom log level and thread names. Parses any
  * "-v [LogLevel]" arguments to set the stderr log level. This argument may
  * be either numeric, or the 4-character string printed in the output.
+ *
+ * If the parameterless overload is used, the `-v` parsing is not used, but
+ * other functionality should still work.
+ *
+ * @note This function is not threadsafe and should only be called from a single
+ * thread (ideally the main thread).
+ * @{
  */
 VTKM_CONT_EXPORT
 VTKM_CONT
 void InitLogging(int& argc, char* argv[]);
+VTKM_CONT_EXPORT
+VTKM_CONT
+void InitLogging();
+/**@}*/
 
 /**
  * Set the range of log levels that will be printed to stderr. All levels

vtkm/cont/testing/UnitTestLogging.cxx

@@ -82,12 +82,11 @@ void RunTests()
 
 } // end anon namespace
 
-int UnitTestLogging(int argc, char* argv[])
+int UnitTestLogging(int, char* [])
 {
-  vtkm::cont::InitLogging(argc, argv);
-  vtkm::cont::SetLogThreadName("main thread");
+  // Test that parameterless init works:
+  vtkm::cont::InitLogging();
 
-  //  return vtkm::cont::testing::Testing::Run(RunTests);
   RunTests();
   return 0;
 }