[libcamera-devel] [PATCH v2 11/30] cam: options: Avoid copies of OptionvValue and KeyValueParser::Options

[Kieran Bingham]

Hi Laurent,

On 12/07/2021 22:56, Laurent Pinchart wrote:
> The OptionValue toKeyValues() and toArray() functions return a copy of
> the values. This is unnecessary, and can cause use-after-free issues
> when taking references to the return values. Return references instead
> to optimize the implementation and avoid issues.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> ---
> Changes since v1:
> 
> - assert() on undefined behaviour
> ---
>  src/cam/options.cpp | 24 ++++++++++++------------
>  src/cam/options.h   |  4 ++--
>  2 files changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/src/cam/options.cpp b/src/cam/options.cpp
> index fda6d9764ac5..aa3035fdf364 100644
> --- a/src/cam/options.cpp
> +++ b/src/cam/options.cpp
> @@ -631,27 +631,27 @@ std::string OptionValue::toString() const
>  
>  /**
>   * \brief Retrieve the value as a key-value list
> - * \return The option value as a KeyValueParser::Options, or an empty list if
> - * the value type isn't ValueType::ValueKeyValue
> + *
> + * The behaviour is undefined if the value type isn't ValueType::ValueKeyValue.
> + *
> + * \return The option value as a KeyValueParser::Options
>   */
> -KeyValueParser::Options OptionValue::toKeyValues() const
> +const KeyValueParser::Options &OptionValue::toKeyValues() const
>  {
> -	if (type_ != ValueKeyValue)
> -		return KeyValueParser::Options();
> -
> +	assert(type_ == ValueKeyValue);
>  	return keyValues_;
>  }
>  
>  /**
>   * \brief Retrieve the value as an array
> - * \return The option value as a std::vector of OptionValue, or an empty vector
> - * if the value type isn't ValueType::ValueArray
> + *
> + * The behaviour is undefined if the value type isn't ValueType::ValueArray.
> + *
> + * \return The option value as a std::vector of OptionValue
>   */
> -std::vector<OptionValue> OptionValue::toArray() const
> +const std::vector<OptionValue> &OptionValue::toArray() const
>  {
> -	if (type_ != ValueArray)
> -		return std::vector<OptionValue>{};
> -
> +	assert(type_ == ValueArray);
>  	return array_;
>  }
>  
> diff --git a/src/cam/options.h b/src/cam/options.h
> index 210e502a24e1..09cbc8339dd0 100644
> --- a/src/cam/options.h
> +++ b/src/cam/options.h
> @@ -141,8 +141,8 @@ public:
>  
>  	int toInteger() const;
>  	std::string toString() const;
> -	KeyValueParser::Options toKeyValues() const;
> -	std::vector<OptionValue> toArray() const;
> +	const KeyValueParser::Options &toKeyValues() const;
> +	const std::vector<OptionValue> &toArray() const;
>  
>  	const OptionsParser::Options &children() const;
>  
>