[SYCL][UB] Make Command::isHostTask() virtual instead of downcasting on MType

[uditagarwal97]

Problem

Command::isHostTask() deduced the dynamic type of the command from its type tag and then downcast unconditionally:

bool Command::isHostTask() const {
  return (MType == CommandType::RUN_CG) /* host task has this type also */ &&
         ((static_cast<const ExecCGCommand *>(this))->getCG().getType() ==
          CGType::CodeplayHostTask);
}

static_cast to a derived type is undefined behaviour unless the object really is of that type; nothing in the type system enforces RUN_CG => ExecCGCommand, only convention. When the object is a plain Command subobject, getCG() reads MCommandGroup from beyond the end of the allocation.

AddressSanitizer report (ASan+UBSan build, SchedulerTest.DontEnqueueDepsIfOneOfThemIsBlocked):

ERROR: AddressSanitizer: global-buffer-overflow on address ...
READ of size 4 at ... thread T0
    #0 ... in getType sycl/source/detail/cg.hpp:104
    #1 ... in sycl::_V1::detail::Command::isHostTask() const
       sycl/source/detail/scheduler/commands.cpp:246
    #2 ... in isBlocking sycl/source/detail/scheduler/commands.hpp:178
    #3 ... in Scheduler::GraphProcessor::handleBlockingCmd(...)

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Co-Authored-By: Claude Opus 5 (1M context) noreply@anthropic.com

[Copilot]

🟢 Approval recommended

The virtual dispatch preserves existing host-task behavior while safely handling other command subclasses.

Pull request overview

Replaces unsafe type-tag downcasting with virtual dispatch when identifying host-task commands.

Changes:

• Adds a safe default Command::isHostTask() implementation.
• Overrides host-task detection in ExecCGCommand.
• Removes the undefined-behavior-prone downcast.

File summaries

File	Description
sycl/source/detail/scheduler/commands.hpp	Defines virtual host-task detection.
sycl/source/detail/scheduler/commands.cpp	Removes unsafe downcasting logic.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

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[sys-ce-bb]

@intel/llvm-gatekeepers please consider merging