SG-40348: Fix print crashing when called from non-main thread; add warning for other mu commands

src/lib/app/PyTwkApp/PyMuSymbolType.cpp

@@ -45,14 +45,37 @@
 #include <MuTwkApp/EventType.h>
 #include <MuTwkApp/MuInterface.h>
 #include <boost/algorithm/string.hpp>
+#include <boost/thread.hpp>
 #include <half.h>
 #include <sstream>
 #include <stdexcept>
+#include <iostream>
 
 namespace TwkApp
 {
     using namespace std;
 
+    // Thread safety tracking
+    // Default constructor creates "not-a-thread" ID
+    static boost::thread::id s_mainThreadId;
+
+    // Helper function for direct cout printing
+    static PyObject* unsafe_mu_print(PyObject* args)
+    {
+        size_t nargs = PyTuple_Size(args);
+        if (nargs >= 1)
+        {
+            PyObject* arg = PyTuple_GetItem(args, 0);
+            if (PyUnicode_Check(arg))
+            {
+                const char* str = PyUnicode_AsUTF8(arg);
+                if (str)
+                    cout << str;
+            }
+        }
+        Py_RETURN_NONE;
+    }
+
     Mu::FunctionObject*
     createFunctionObjectFromPyObject(const Mu::FunctionType* t, PyObject* pyobj)
     {
@@ -300,6 +323,33 @@ namespace TwkApp
             return NULL;
         }
 
+        // Thread safety check - initialize main thread ID on first call
+        boost::thread::id currentThreadId = boost::this_thread::get_id();
+        if (s_mainThreadId == boost::thread::id()) // Check if uninitialized
+                                                   // (default constructed)
+        {
+            s_mainThreadId = currentThreadId;
+        }
+
+        if (currentThreadId != s_mainThreadId)
+        {
+            // fix mu print commands from python to at least not crash from
+            // non-main thread
+            //  (because python print is often used to debug python code, so
+            //  we'll tolerate this because print is likely redirected to the RV
+            //  console)
+            if (self->function->fullyQualifiedName() == "extra_commands._print")
+            {
+                return unsafe_mu_print(args);
+            }
+
+            // this cout will probably get redirected to the RV console, or go
+            // to the terminal window.
+            cout << "WARNING: Mu " << self->function->fullyQualifiedName()
+                 << "() called from non-main thread, will eventually crash "
+                 << "(Mu isn't thread-safe)." << endl;
+        }
+
         size_t nargs = PyTuple_Size(args);
 
         Mu::Function::ArgumentVector muargs(self->function->numArgs());