Re: [OE-core] [PATCH] gn: remove gcc override

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Fri, 2025-10-03 at 16:02 -0400, Jon Mason via lists.openembedded.org
wrote:
> When compiling gn with clang, the following errors are being seen
> (with
> qemuarm64-secureboot machine, possibly others):
> 
> In file included from /usr/include/c++/12/string:40,
>                  from ../sources/gn-
> 0+git/src/base/strings/string_number_conversions.h:11,
>                  from ../sources/gn-0+git/src/gn/operators.cc:10:
> In static member function ‘static constexpr void
> std::char_traits<char>::assign(char_type&, const char_type&)’,
>     inlined from ‘static constexpr void
> std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy(_CharT*,
> const _CharT*, size_type) [with _CharT = char; _Traits =
> std::char_traits<char>; _Alloc = std::allocator<char>]’ at
> /usr/include/c++/12/bits/basic_string.h:421:23,
>     inlined from ‘constexpr std::__cxx11::basic_string<_CharT,
> _Traits, _Allocator>& std::__cxx11::basic_string<_CharT, _Traits,
> _Alloc>::_M_replace(size_type, size_type, const _CharT*, size_type)
> [with _CharT = char; _Traits = std::char_traits<char>; _Alloc =
> std::allocator<char>]’ at
> /usr/include/c++/12/bits/basic_string.tcc:532:22,
>     inlined from ‘constexpr std::__cxx11::basic_string<_CharT,
> _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits,
> _Alloc>::assign(const _CharT*) [with _CharT = char; _Traits =
> std::char_traits<char>; _Alloc = std::allocator<char>]’ at
> /usr/include/c++/12/bits/basic_string.h:1647:19,
>     inlined from ‘constexpr std::__cxx11::basic_string<_CharT,
> _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits,
> _Alloc>::operator=(const _CharT*) [with _CharT = char; _Traits =
> std::char_traits<char>; _Alloc = std::allocator<char>]’ at
> /usr/include/c++/12/bits/basic_string.h:815:28,
>     inlined from ‘Err {anonymous}::MakeOverwriteError(const
> BinaryOpNode*, const Value&)’ at ../sources/gn-
> 0+git/src/gn/operators.cc:202:17:
> /usr/include/c++/12/bits/char_traits.h:354:16: error: ‘((const
> std::char_traits<char>::char_type*)((char*)&empty_def +
> offsetof(std::__cxx11::string, std::__cxx11::basic_string<char,
> std::char_traits<char>, std::allocator<char> >::<unnamed>)))[2]’ may
> be used uninitialized [-Werror=maybe-uninitialized]
>   354 |         __c1 = __c2;
>       |                ^~~~
> ../sources/gn-0+git/src/gn/operators.cc: In function ‘Err
> {anonymous}::MakeOverwriteError(const BinaryOpNode*, const Value&)’:
> ../sources/gn-0+git/src/gn/operators.cc:198:15: note: ‘empty_def’
> declared here
>   198 |   std::string empty_def;
>       |               ^~~~~~~~~
> In static member function ‘static constexpr void
> std::char_traits<char>::assign(char_type&, const char_type&)’,
>     inlined from ‘static constexpr void
> std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy(_CharT*,
> const _CharT*, size_type) [with _CharT = char; _Traits =
> std::char_traits<char>; _Alloc = std::allocator<char>]’ at
> /usr/include/c++/12/bits/basic_string.h:421:23,
>     inlined from ‘constexpr std::__cxx11::basic_string<_CharT,
> _Traits, _Allocator>& std::__cxx11::basic_string<_CharT, _Traits,
> _Alloc>::_M_replace(size_type, size_type, const _CharT*, size_type)
> [with _CharT = char; _Traits = std::char_traits<char>; _Alloc =
> std::allocator<char>]’ at
> /usr/include/c++/12/bits/basic_string.tcc:532:22,
>     inlined from ‘constexpr std::__cxx11::basic_string<_CharT,
> _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits,
> _Alloc>::assign(const _CharT*) [with _CharT = char; _Traits =
> std::char_traits<char>; _Alloc = std::allocator<char>]’ at
> /usr/include/c++/12/bits/basic_string.h:1647:19,
>     inlined from ‘constexpr std::__cxx11::basic_string<_CharT,
> _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits,
> _Alloc>::operator=(const _CharT*) [with _CharT = char; _Traits =
> std::char_traits<char>; _Alloc = std::allocator<char>]’ at
> /usr/include/c++/12/bits/basic_string.h:815:28,
>     inlined from ‘Err {anonymous}::MakeOverwriteError(const
> BinaryOpNode*, const Value&)’ at ../sources/gn-
> 0+git/src/gn/operators.cc:205:17:
> /usr/include/c++/12/bits/char_traits.h:354:16: error: ‘((const
> std::char_traits<char>::char_type*)((char*)&empty_def +
> offsetof(std::__cxx11::string, std::__cxx11::basic_string<char,
> std::char_traits<char>, std::allocator<char> >::<unnamed>)))[2]’ may
> be used uninitialized [-Werror=maybe-uninitialized]
>   354 |         __c1 = __c2;
>       |                ^~~~
> ../sources/gn-0+git/src/gn/operators.cc: In function ‘Err
> {anonymous}::MakeOverwriteError(const BinaryOpNode*, const Value&)’:
> ../sources/gn-0+git/src/gn/operators.cc:198:15: note: ‘empty_def’
> declared here
>   198 |   std::string empty_def;
>       |               ^~~~~~~~~
> cc1plus: all warnings being treated as errors
> 
> Remove the toolchain-gcc override to allow the cflag
> -Wno-error=maybe-uninitialized to be applied.
> 
> Signed-off-by: Jon Mason <jon.mason@arm.com>
> ---
>  meta/recipes-devtools/gn/gn_git.bb | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/meta/recipes-devtools/gn/gn_git.bb b/meta/recipes-
> devtools/gn/gn_git.bb
> index d8896609b193..2443ea7139f4 100644
> --- a/meta/recipes-devtools/gn/gn_git.bb
> +++ b/meta/recipes-devtools/gn/gn_git.bb
> @@ -49,4 +49,4 @@ BBCLASSEXTEND = "native"
>  
>  COMPATIBLE_HOST = "^(?!riscv32).*"
>  
> -CFLAGS:append:toolchain-gcc = " -Wno-error=maybe-uninitialized"
> +CFLAGS:append = " -Wno-error=maybe-uninitialized"

In that case can you drop the append and just make it a += please?

Cheers,

Richard