Implementation:NVIDIA DALI Cpplint

Knowledge Sources	NVIDIA_DALI
Domains	Code_Quality, Linting
Last Updated	2026-02-08 16:00 GMT

Overview

Customized Google C++ style linter that checks DALI's C++ source files for compliance with coding standards, supporting .cc, .cpp, .cu, .cuh, and .h file extensions.

Description

This file (third_party/cpplint.py) is NVIDIA's customized fork of Google's cpplint tool, originally developed by Google Inc. and extended with NVIDIA-specific modifications (copyright 2017-2022). At 6,244 lines, it is a comprehensive static analysis tool that identifies potential style violations in C++ code based on the Google C++ Style Guide.

The linter organizes its checks into five major categories: build (class definitions, C++11/14 usage, deprecated constructs, header guards, includes), legal (copyright notices), readability (casting style, braces, constructors, function size, namespace formatting, UTF-8 compliance), runtime (array usage, casting, explicit constructors, integer types, memory operations, thread safety), and whitespace (blank lines, braces, commas, comments, indentation, line length, operators, tabs). Each violation is assigned a confidence score from 1 to 5, with 5 indicating certainty.

The tool supports extensive configuration through command-line flags including --filter for enabling/disabling specific check categories, --linelength for maximum line width, --root for header guard derivation, --extensions for linted file types (defaulting to .cc, .cpp, .cu, .cuh, .h), and --headers for header file recognition. Per-directory configuration is supported via CPPLINT.cfg files that can set filters, exclude files by regex, configure line length, and establish root directories. The set noparent directive prevents upward traversal of configuration inheritance.

The main entry point parses arguments via ParseArguments(), processes each file through ProcessFile(), and exits with a non-zero status if any errors are found. NOLINT comments in source code suppress false positives on specific lines.

Usage

This linter is used in DALI's CI pipeline and by developers to enforce consistent C++ coding style across the DALI codebase. It is invoked on individual files or directories as part of pre-commit checks or automated quality gates.

Code Reference

Source Location

• Repository: NVIDIA_DALI
• File: third_party/cpplint.py
• Lines: 1-6244

Signature

# Error categories (partial list)
_ERROR_CATEGORIES = [
    'build/class', 'build/c++11', 'build/c++14', 'build/header_guard',
    'build/include', 'build/include_order', 'build/namespaces',
    'legal/copyright',
    'readability/braces', 'readability/casting', 'readability/fn_size',
    'runtime/arrays', 'runtime/casting', 'runtime/explicit', 'runtime/int',
    'whitespace/blank_line', 'whitespace/braces', 'whitespace/indent',
    'whitespace/line_length', 'whitespace/tab',
    # ... and many more
]

_DEFAULT_FILTERS = ['-build/include_alpha']

# Key functions
def ProcessFile(filename, vlevel, extra_check_functions=[]): ...
def ProcessFileData(filename, file_extension, lines, error, extra_check_functions=[]): ...
def ParseArguments(args): ...
def main(): ...

Import

# Run as standalone script
python third_party/cpplint.py [--verbose=#] [--filter=...] <file> [file] ...

# Example
python third_party/cpplint.py --linelength=100 dali/pipeline/pipeline.cc

I/O Contract

Inputs

Name	Type	Required	Description
file(s)	positional args	Yes	One or more C++ source files to lint
--verbose	int (0-5)	No	Restrict errors to certain verbosity levels
--filter	str	No	Comma-separated category filters: +enable, -disable
--linelength	int	No	Maximum allowed line length (default: 80)
--root	str	No	Root directory for deriving header guard CPP variable names
--extensions	str	No	Comma-separated list of file extensions to lint (default: cc,cpp,cu,cuh,h)
--headers	str	No	Comma-separated header extensions to treat as .h
--output	str	No	Output format: emacs (default), vs7, or eclipse
--counting	str	No	Error counting style: total, toplevel, or detailed
--quiet	flag	No	Suppress output if no errors found
CPPLINT.cfg	file	No	Per-directory configuration files with filter, linelength, root, exclude_files settings

Outputs

Name	Type	Description
Lint warnings	stderr	Style violations with file, line number, category, confidence level, and description
Error counts	stderr	Summary count of total errors found (by category if --counting specified)
Exit code	int	0 if no errors, 1 if errors found

Usage Examples

Lint a single file

python third_party/cpplint.py dali/pipeline/pipeline.cc

Lint with custom filters and line length

python third_party/cpplint.py \
    --linelength=100 \
    --filter=-whitespace/indent,-build/include_order \
    --verbose=3 \
    dali/kernels/*.cu dali/kernels/*.cuh

Use with CPPLINT.cfg

# CPPLINT.cfg placed in project root
set noparent
filter=-build/include_alpha,+build/include_order
linelength=100
root=dali
exclude_files=.*_test\.cc

Related Pages

• Environment:NVIDIA_DALI_CUDA_GPU_Environment