Fix userdata binding corner case (#1673)

This includes two fixes:

 1) When registering symbols that need user data, sort the entries in
 the set so the layer number is ignored. A needed udata iteam shouldn't
 depend on the layer and separating them makes find_userdata_index()
 sometimes find an index with different derivs status.

 2) osl_bind_interpolated_param() is memcpy'ing derivs that might not
 be there, yielding corrupted derivs and possibly a crash.

Signed-off-by: Alejandro Conty <[email protected]>

Author: aconty

src/liboslexec/oslexec_pvt.h

@@ -191,8 +191,10 @@ struct UserDataNeeded {
     {
         if (a.name != b.name)
             return a.name < b.name;
-        if (a.layer_num != b.layer_num)
-            return a.layer_num < b.layer_num;
+        // Checking for layer_num means that if derivs differ find_userdata_index
+        // may find the wrong layer symbol with the wrong derivs setting.
+        //if (a.layer_num != b.layer_num)
+        //    return a.layer_num < b.layer_num;
         if (a.type.basetype != b.type.basetype)
             return a.type.basetype < b.type.basetype;
         if (a.type.aggregate != b.type.aggregate)

src/liboslexec/shadingsys.cpp

@@ -4469,8 +4469,13 @@ osl_bind_interpolated_param(void* sg_, const void* name, long long type,
         sg->context->incr_get_userdata_calls();
     }
     if (status == 2) {
+        int udata_size = (userdata_has_derivs ? 3 : 1) * TYPEDESC(type).size();
         // If userdata was present, copy it to the shader variable
-        memcpy(symbol_data, userdata_data, symbol_data_size);
+        memcpy(symbol_data, userdata_data,
+               std::min(symbol_data_size, udata_size));
+        if (symbol_data_size > udata_size)
+            memset((char*)symbol_data + udata_size, 0,
+                   symbol_data_size - udata_size);
         return 1;
     }
     return 0;  // no such user data