[SYCL] Fix uninitialized fields Coverity hits (#15237)

This PR fixes Coverity hits regarding uninitialized class fields in the
runtime.

I'd like to bring attention to `sycl_mem_obj_t.hpp` however: There, I
have initialized `MSizeInBytes` of the `SYCLMemObjT` class to 0: This
should not cause any problems (at least not more), as currently all
subclasses of `SYCLMemObjT` that actually use the `MSizeInBytes` have it
defined (`buffer_impl`, `image_impl`) when their respective constructors
are called. However, this does mean programmers must remember to
initialize `MSizeInBytes` when using `image_impl`.

To avoid this, I could rewrite some of the constructors in e.g.
`image_impl` and `SYCLMemObjT`, but I'd like to not overcomplicate the
problem here. So I was hoping for some other opinions: Is initializing
as 0 sufficient, or should I go ahead and make the changes to the
constructors anyway to be safe? Thanks in advance!

Author: ianayl

sycl/source/detail/event_impl.hpp

@@ -390,7 +390,7 @@ class event_impl {
   // If this event represents a submission to a
   // ur_exp_command_buffer_sync_point_t the sync point for that submission is
   // stored here.
-  ur_exp_command_buffer_sync_point_t MSyncPoint;
+  ur_exp_command_buffer_sync_point_t MSyncPoint = 0;
 
   // If this event represents a submission to a
   // ur_exp_command_buffer_command_handle_t the command-buffer command

sycl/source/detail/queue_impl.hpp

@@ -239,7 +239,9 @@ class queue_impl {
         MIsInorder(has_property<property::queue::in_order>()),
         MDiscardEvents(
             has_property<ext::oneapi::property::queue::discard_events>()),
-        MIsProfilingEnabled(has_property<property::queue::enable_profiling>()) {
+        MIsProfilingEnabled(has_property<property::queue::enable_profiling>()),
+        MQueueID{
+            MNextAvailableQueueID.fetch_add(1, std::memory_order_relaxed)} {
     queue_impl_interop(UrQueue);
   }
 

sycl/source/detail/scheduler/commands.cpp

@@ -994,9 +994,9 @@ const char *Command::getBlockReason() const {
     return "A Buffer is locked by the host accessor";
   case BlockReason::HostTask:
     return "Blocked by host task";
+  default:
+    return "Unknown block reason";
   }
-
-  return "Unknown block reason";
 }
 
 void Command::copySubmissionCodeLocation() {

sycl/source/detail/scheduler/commands.hpp

@@ -321,10 +321,10 @@ class Command {
   /// Used for marking the node during graph traversal.
   Marks MMarks;
 
-  enum class BlockReason : int { HostAccessor = 0, HostTask };
+  enum class BlockReason : int { Unset = -1, HostAccessor = 0, HostTask };
 
   // Only have reasonable value while MIsBlockable is true
-  BlockReason MBlockReason;
+  BlockReason MBlockReason = BlockReason::Unset;
 
   /// Describes the status of the command.
   std::atomic<EnqueueResultT::ResultT> MEnqueueStatus;

sycl/source/detail/sycl_mem_obj_t.hpp

@@ -353,7 +353,7 @@ class SYCLMemObjT : public SYCLMemObjI {
   // Indicates if memory object should write memory to the host on destruction.
   bool MNeedWriteBack;
   // Size of memory.
-  size_t MSizeInBytes;
+  size_t MSizeInBytes = 0;
   // User's pointer passed to constructor.
   void *MUserPtr;
   // Copy of memory passed by user to constructor.