Avoid warning about unused variables

[miscco]

Commonly the NVTX annotations do not get a variable assigned

Picked up in CCCL CI

[greptile-apps]

Greptile Overview

Greptile Summary

Added [[maybe_unused]] attribute to NVTX range variables in kernel fusion examples to suppress compiler warnings when NVTX is disabled.

Key Changes

• unfused_range and fused_range variables now marked with [[maybe_unused]] attribute
• Variables are still properly defined and used by MATX_NVTX_END_RANGE macro
• When NVTX is disabled, these macros expand to no-ops, making the variables technically unused
• The [[maybe_unused]] attribute correctly suppresses warnings in this configuration

Previous Review Thread Clarification

The previous comments claiming variables are "now undefined" are incorrect. The variables remain properly defined and assigned. The [[maybe_unused]] attribute only suppresses compiler warnings about unused variables in certain build configurations.

Confidence Score: 5/5

• This PR is safe to merge with no risk
• The changes are minimal and correct. The [[maybe_unused]] attribute is the appropriate solution for variables that are used in some configurations but not others. The previous review comments incorrectly stated the variables were undefined, but they remain properly defined and used when NVTX is enabled.
• No files require special attention

Important Files Changed

Filename	Overview
examples/kernel_fusion.cu	Added [[maybe_unused]] to NVTX range variables to suppress warnings when NVTX is disabled
docs_input/notebooks/gtc_lab/samples/kernel_fusion.cu	Added [[maybe_unused]] to NVTX range variables to suppress warnings when NVTX is disabled

Sequence Diagram

sequenceDiagram
    participant Code as kernel_fusion.cu
    participant NVTX as NVTX Macros
    participant Compiler as C++ Compiler
    
    Note over Code,Compiler: When NVTX is enabled
    Code->>NVTX: MATX_NVTX_START_RANGE("Unfused Kernels")
    NVTX->>NVTX: autoCreateNvtxEvent() returns int ID
    NVTX-->>Code: Returns range ID
    Code->>Code: Store in [[maybe_unused]] int unfused_range
    Code->>Code: Execute operations
    Code->>NVTX: MATX_NVTX_END_RANGE(unfused_range)
    NVTX->>NVTX: endEvent(id) uses the variable
    
    Note over Code,Compiler: When NVTX is disabled
    Code->>NVTX: MATX_NVTX_START_RANGE("Unfused Kernels")
    NVTX-->>Code: Macro expands to 0
    Code->>Code: Store in [[maybe_unused]] int unfused_range = 0
    Code->>Code: Execute operations
    Code->>NVTX: MATX_NVTX_END_RANGE(unfused_range)
    NVTX-->>Code: Macro expands to no-op
    Note over Code,Compiler: [[maybe_unused]] prevents warning

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[greptile-apps]

_{2 files reviewed, 5 comments}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

unfused_range is now undefined. MATX_NVTX_START_RANGE was changed to not assign to a variable, but line 36 still references unfused_range in MATX_NVTX_END_RANGE(unfused_range).

Suggested change

	MATX_NVTX_START_RANGE("Unfused Kernels");
	(result = cos(C)).run(exec);
	(result = result / D).run(exec);
	(result = result * B).run(exec);
	MATX_NVTX_END_RANGE(unfused_range);
	[[maybe_unused]] int unfused_range = MATX_NVTX_START_RANGE("Unfused Kernels");
	(result = cos(C)).run(exec);
	(result = result / D).run(exec);
	(result = result * B).run(exec);
	MATX_NVTX_END_RANGE(unfused_range);

[greptile-apps]

fused_range is now undefined. MATX_NVTX_START_RANGE was changed to not assign to a variable, but line 41 still references fused_range in MATX_NVTX_END_RANGE(fused_range).

Suggested change

	MATX_NVTX_START_RANGE("Fused Operation");
	(A = B * cos(C)/D).run(exec);
	MATX_NVTX_END_RANGE(fused_range);
	[[maybe_unused]] int fused_range = MATX_NVTX_START_RANGE("Fused Operation");
	(A = B * cos(C)/D).run(exec);
	MATX_NVTX_END_RANGE(fused_range);

[greptile-apps]

Additional Comments (1)

docs_input/notebooks/gtc_lab/samples/kernel_fusion.cu
Duplicate MATX_EXIT_HANDLER() call on line 53 (already called on line 52)

}

[greptile-apps]

_{2 files reviewed, no comments}

_{Edit Code Review Agent Settings | Greptile}

[cliffburdick]

/build