libcamera: yaml_parser: Fix uninitialized variable warning
diff mbox series

Message ID 20260128162649.3263861-1-laurent.pinchart@ideasonboard.com
State New
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Series
  • libcamera: yaml_parser: Fix uninitialized variable warning
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Commit Message

Laurent Pinchart Jan. 28, 2026, 4:26 p.m. UTC 
gcc 14.3.0, cross-compiling from amd64 to arm64, warns about a possibly
uninitialized variable in YamlObject::Getter<>::get():

In file included from ../../include/libcamera/internal/yaml_parser.h:12,
                 from ../../src/libcamera/yaml_parser.cpp:8:
In constructor ‘constexpr std::_Optional_payload_base<_Tp>::_Storage<_Up, <anonymous> >::_Storage(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}; _Up = unsigned char; bool <anonymous> = true; _Tp = unsigned char]’,
    inlined from ‘constexpr std::_Optional_payload_base<_Tp>::_Optional_payload_base(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}; _Tp = unsigned char]’ at include/c++/14.3.0/optional:122:4,
    inlined from ‘constexpr std::_Optional_payload<unsigned char, true, true, true>::_Optional_payload(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}][inherited from std::_Optional_payload_base<unsigned char>]’ at include/c++/14.3.0/optional:337:42,
    inlined from ‘constexpr std::_Optional_base<_Tp, true, true>::_Optional_base(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}; typename std::enable_if<is_constructible_v<_Tp, _Args ...>, bool>::type <anonymous> = false; _Tp = unsigned char]’ at include/c++/14.3.0/optional:648:4,
    inlined from ‘constexpr std::optional<_Tp>::optional(_Up&&) [with _Up = unsigned char; typename std::enable_if<__and_v<std::__not_<std::is_same<std::optional<_Tp>, typename std::remove_cv<typename std::remove_reference<_Up>::type>::type> >, std::__not_<std::is_same<std::in_place_t, typename std::remove_cv<typename std::remove_reference<_Up>::type>::type> >, std::is_constructible<_T1, _U1>, std::is_convertible<_Iter, _Iterator> >, bool>::type <anonymous> = true; _Tp = unsigned char]’ at include/c++/14.3.0/optional:747:47,
    inlined from ‘std::optional<_Tp> libcamera::YamlObject::Getter<T, typename std::enable_if<(((((is_same_v<signed char, T> || is_same_v<unsigned char, T>) || is_same_v<short int, T>) || is_same_v<short unsigned int, T>) || is_same_v<int, T>) || is_same_v<unsigned int, T>), void>::type>::get(const libcamera::YamlObject&) const [with T = unsigned char]’ at ../../src/libcamera/yaml_parser.cpp:172:10:
include/c++/14.3.0/optional:210:15: error: ‘value’ may be used uninitialized [-Werror=maybe-uninitialized]
  210 |             : _M_value(std::forward<_Args>(__args)...)
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../src/libcamera/yaml_parser.cpp: In member function ‘std::optional<_Tp> libcamera::YamlObject::Getter<T, typename std::enable_if<(((((is_same_v<signed char, T> || is_same_v<unsigned char, T>) || is_same_v<short int, T>) || is_same_v<short unsigned int, T>) || is_same_v<int, T>) || is_same_v<unsigned int, T>), void>::type>::get(const libcamera::YamlObject&) const [with T = unsigned char]’:
../../src/libcamera/yaml_parser.cpp:165:19: note: ‘value’ was declared here
  165 |                 T value;
      |                   ^~~~~

This appears to be a false positive, as the std::from_chars() function
should set value when it returns without an error. Commit bb1d216113bc
("libcamera: base: log: Fix uninitialized variable warning") fixed a
similar warning with gcc 13.3.0.

The warning is easy to work around by initializing the variable, and
doing so shouldn't be too costly as the type T is restricted to being an
integer. Fix the build by doing so.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 src/libcamera/yaml_parser.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


base-commit: 186e5cf9ac74cc495384c0af5a055c33a43d9ecc

Comments

Kieran Bingham Jan. 28, 2026, 4:29 p.m. UTC | #1 
Quoting Laurent Pinchart (2026-01-28 16:26:49)
> gcc 14.3.0, cross-compiling from amd64 to arm64, warns about a possibly
> uninitialized variable in YamlObject::Getter<>::get():
> 
> In file included from ../../include/libcamera/internal/yaml_parser.h:12,
>                  from ../../src/libcamera/yaml_parser.cpp:8:
> In constructor ‘constexpr std::_Optional_payload_base<_Tp>::_Storage<_Up, <anonymous> >::_Storage(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}; _Up = unsigned char; bool <anonymous> = true; _Tp = unsigned char]’,
>     inlined from ‘constexpr std::_Optional_payload_base<_Tp>::_Optional_payload_base(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}; _Tp = unsigned char]’ at include/c++/14.3.0/optional:122:4,
>     inlined from ‘constexpr std::_Optional_payload<unsigned char, true, true, true>::_Optional_payload(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}][inherited from std::_Optional_payload_base<unsigned char>]’ at include/c++/14.3.0/optional:337:42,
>     inlined from ‘constexpr std::_Optional_base<_Tp, true, true>::_Optional_base(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}; typename std::enable_if<is_constructible_v<_Tp, _Args ...>, bool>::type <anonymous> = false; _Tp = unsigned char]’ at include/c++/14.3.0/optional:648:4,
>     inlined from ‘constexpr std::optional<_Tp>::optional(_Up&&) [with _Up = unsigned char; typename std::enable_if<__and_v<std::__not_<std::is_same<std::optional<_Tp>, typename std::remove_cv<typename std::remove_reference<_Up>::type>::type> >, std::__not_<std::is_same<std::in_place_t, typename std::remove_cv<typename std::remove_reference<_Up>::type>::type> >, std::is_constructible<_T1, _U1>, std::is_convertible<_Iter, _Iterator> >, bool>::type <anonymous> = true; _Tp = unsigned char]’ at include/c++/14.3.0/optional:747:47,
>     inlined from ‘std::optional<_Tp> libcamera::YamlObject::Getter<T, typename std::enable_if<(((((is_same_v<signed char, T> || is_same_v<unsigned char, T>) || is_same_v<short int, T>) || is_same_v<short unsigned int, T>) || is_same_v<int, T>) || is_same_v<unsigned int, T>), void>::type>::get(const libcamera::YamlObject&) const [with T = unsigned char]’ at ../../src/libcamera/yaml_parser.cpp:172:10:
> include/c++/14.3.0/optional:210:15: error: ‘value’ may be used uninitialized [-Werror=maybe-uninitialized]
>   210 |             : _M_value(std::forward<_Args>(__args)...)
>       |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../../src/libcamera/yaml_parser.cpp: In member function ‘std::optional<_Tp> libcamera::YamlObject::Getter<T, typename std::enable_if<(((((is_same_v<signed char, T> || is_same_v<unsigned char, T>) || is_same_v<short int, T>) || is_same_v<short unsigned int, T>) || is_same_v<int, T>) || is_same_v<unsigned int, T>), void>::type>::get(const libcamera::YamlObject&) const [with T = unsigned char]’:
> ../../src/libcamera/yaml_parser.cpp:165:19: note: ‘value’ was declared here
>   165 |                 T value;
>       |                   ^~~~~
> 
> This appears to be a false positive, as the std::from_chars() function
> should set value when it returns without an error. Commit bb1d216113bc
> ("libcamera: base: log: Fix uninitialized variable warning") fixed a
> similar warning with gcc 13.3.0.
> 
> The warning is easy to work around by initializing the variable, and
> doing so shouldn't be too costly as the type T is restricted to being an
> integer. Fix the build by doing so.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Odd that this hasn't come up elsewhere but it's not a difficult fix so:


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

> ---
>  src/libcamera/yaml_parser.cpp | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/libcamera/yaml_parser.cpp b/src/libcamera/yaml_parser.cpp
> index a5e424615c26..e13b5faedd81 100644
> --- a/src/libcamera/yaml_parser.cpp
> +++ b/src/libcamera/yaml_parser.cpp
> @@ -162,7 +162,7 @@ struct YamlObject::Getter<T, std::enable_if_t<
>                         return std::nullopt;
>  
>                 const std::string &str = obj.value_;
> -               T value;
> +               T value = {};
>  
>                 auto [ptr, ec] = std::from_chars(str.data(), str.data() + str.size(),
>                                                  value);
> 
> base-commit: 186e5cf9ac74cc495384c0af5a055c33a43d9ecc
> -- 
> Regards,
> 
> Laurent Pinchart
>
Barnabás Pőcze Jan. 28, 2026, 4:34 p.m. UTC | #2 
2026. 01. 28. 17:26 keltezéssel, Laurent Pinchart írta:
> gcc 14.3.0, cross-compiling from amd64 to arm64, warns about a possibly
> uninitialized variable in YamlObject::Getter<>::get():
> 
> In file included from ../../include/libcamera/internal/yaml_parser.h:12,
>                   from ../../src/libcamera/yaml_parser.cpp:8:
> In constructor ‘constexpr std::_Optional_payload_base<_Tp>::_Storage<_Up, <anonymous> >::_Storage(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}; _Up = unsigned char; bool <anonymous> = true; _Tp = unsigned char]’,
>      inlined from ‘constexpr std::_Optional_payload_base<_Tp>::_Optional_payload_base(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}; _Tp = unsigned char]’ at include/c++/14.3.0/optional:122:4,
>      inlined from ‘constexpr std::_Optional_payload<unsigned char, true, true, true>::_Optional_payload(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}][inherited from std::_Optional_payload_base<unsigned char>]’ at include/c++/14.3.0/optional:337:42,
>      inlined from ‘constexpr std::_Optional_base<_Tp, true, true>::_Optional_base(std::in_place_t, _Args&& ...) [with _Args = {unsigned char}; typename std::enable_if<is_constructible_v<_Tp, _Args ...>, bool>::type <anonymous> = false; _Tp = unsigned char]’ at include/c++/14.3.0/optional:648:4,
>      inlined from ‘constexpr std::optional<_Tp>::optional(_Up&&) [with _Up = unsigned char; typename std::enable_if<__and_v<std::__not_<std::is_same<std::optional<_Tp>, typename std::remove_cv<typename std::remove_reference<_Up>::type>::type> >, std::__not_<std::is_same<std::in_place_t, typename std::remove_cv<typename std::remove_reference<_Up>::type>::type> >, std::is_constructible<_T1, _U1>, std::is_convertible<_Iter, _Iterator> >, bool>::type <anonymous> = true; _Tp = unsigned char]’ at include/c++/14.3.0/optional:747:47,
>      inlined from ‘std::optional<_Tp> libcamera::YamlObject::Getter<T, typename std::enable_if<(((((is_same_v<signed char, T> || is_same_v<unsigned char, T>) || is_same_v<short int, T>) || is_same_v<short unsigned int, T>) || is_same_v<int, T>) || is_same_v<unsigned int, T>), void>::type>::get(const libcamera::YamlObject&) const [with T = unsigned char]’ at ../../src/libcamera/yaml_parser.cpp:172:10:
> include/c++/14.3.0/optional:210:15: error: ‘value’ may be used uninitialized [-Werror=maybe-uninitialized]
>    210 |             : _M_value(std::forward<_Args>(__args)...)
>        |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../../src/libcamera/yaml_parser.cpp: In member function ‘std::optional<_Tp> libcamera::YamlObject::Getter<T, typename std::enable_if<(((((is_same_v<signed char, T> || is_same_v<unsigned char, T>) || is_same_v<short int, T>) || is_same_v<short unsigned int, T>) || is_same_v<int, T>) || is_same_v<unsigned int, T>), void>::type>::get(const libcamera::YamlObject&) const [with T = unsigned char]’:
> ../../src/libcamera/yaml_parser.cpp:165:19: note: ‘value’ was declared here
>    165 |                 T value;
>        |                   ^~~~~
> 
> This appears to be a false positive, as the std::from_chars() function
> should set value when it returns without an error. Commit bb1d216113bc
> ("libcamera: base: log: Fix uninitialized variable warning") fixed a
> similar warning with gcc 13.3.0.
> 
> The warning is easy to work around by initializing the variable, and
> doing so shouldn't be too costly as the type T is restricted to being an
> integer. Fix the build by doing so.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---

Reviewed-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>


>   src/libcamera/yaml_parser.cpp | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/libcamera/yaml_parser.cpp b/src/libcamera/yaml_parser.cpp
> index a5e424615c26..e13b5faedd81 100644
> --- a/src/libcamera/yaml_parser.cpp
> +++ b/src/libcamera/yaml_parser.cpp
> @@ -162,7 +162,7 @@ struct YamlObject::Getter<T, std::enable_if_t<
>   			return std::nullopt;
>   
>   		const std::string &str = obj.value_;
> -		T value;
> +		T value = {};
>   
>   		auto [ptr, ec] = std::from_chars(str.data(), str.data() + str.size(),
>   						 value);
> 
> base-commit: 186e5cf9ac74cc495384c0af5a055c33a43d9ecc

Patch
diff mbox series 

diff --git a/src/libcamera/yaml_parser.cpp b/src/libcamera/yaml_parser.cpp
index a5e424615c26..e13b5faedd81 100644
--- a/src/libcamera/yaml_parser.cpp
+++ b/src/libcamera/yaml_parser.cpp
@@ -162,7 +162,7 @@  struct YamlObject::Getter<T, std::enable_if_t<
 			return std::nullopt;
 
 		const std::string &str = obj.value_;
-		T value;
+		T value = {};
 
 		auto [ptr, ec] = std::from_chars(str.data(), str.data() + str.size(),
 						 value);