[libcamera-devel] [PATCH v1 2/2] libcamera: base: utils: Support C libraries lacking locale support

[Kieran Bingham]

Quoting Laurent Pinchart via libcamera-devel (2023-01-08 21:43:57)
> Not all C libraries include support for locale objects (locale_t) and
> the strto*_l() family of functions. A notable example is uClibc that can
> be compiled with a hardcoded "C" locale. Compilation then fails as the
> newlocale(), freelocale() and strtod_l() functions are not defined.
> 
> Fix the compilation breakage by checking for the availability of
> newlocale(), and fall back to strtod() when the function isn't
> available. This may not lead to the correct result if support for locale
> objects isn't available and the locale isn't hardcoded to "C", but that
> is such a corner case that we will likely never encounter it.

Agreed.

And this is fine by me, as long as it all compiles. I'm not yet aware of
anyone actually using libcamera with uClibc (I'd love to hear if anyone
is using it ...) - so I think this is just to maintain compatibility for
now.

Does the same issue happen in musl - or does that have locale support ?

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

> Fixes: e8ae254970cf ("libcamera: yaml_parser: Use C locale")
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  meson.build                  |  4 ++++
>  src/libcamera/base/utils.cpp | 12 ++++++++++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/meson.build b/meson.build
> index e86673dd5c0c..7dcd34d3e6b3 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -72,6 +72,10 @@ if cc.has_header_symbol('unistd.h', 'issetugid')
>      config_h.set('HAVE_ISSETUGID', 1)
>  endif
>  
> +if cc.has_header_symbol('locale.h', 'newlocale', prefix : '#define _GNU_SOURCE')
> +    config_h.set('HAVE_NEWLOCALE', 1)
> +endif
> +
>  if cc.has_header_symbol('stdlib.h', 'secure_getenv', prefix : '#define _GNU_SOURCE')
>      config_h.set('HAVE_SECURE_GETENV', 1)
>  endif
> diff --git a/src/libcamera/base/utils.cpp b/src/libcamera/base/utils.cpp
> index 4a239427a4d9..ac3e1311995e 100644
> --- a/src/libcamera/base/utils.cpp
> +++ b/src/libcamera/base/utils.cpp
> @@ -464,6 +464,8 @@ std::string toAscii(const std::string &str)
>   * \a b
>   */
>  
> +#if HAVE_NEWLOCALE
> +
>  namespace {
>  
>  /*
> @@ -493,6 +495,8 @@ Locale cLocale("C");
>  
>  } /* namespace */
>  
> +#endif /* HAVE_NEWLOCALE */
> +
>  /**
>   * \brief Convert a string to a double independently of the current locale
>   * \param[in] nptr The string to convert
> @@ -506,7 +510,15 @@ Locale cLocale("C");
>   */
>  double strtod(const char *__restrict nptr, char **__restrict endptr)
>  {
> +#if HAVE_NEWLOCALE
>         return strtod_l(nptr, endptr, cLocale.locale());
> +#else
> +       /*
> +        * If the libc implementation doesn't provide locale object support,
> +        * assume that strtod() is locale-independent.
> +        */
> +       return strtod(nptr, endptr);
> +#endif
>  }
>  
>  } /* namespace utils */
> -- 
> Regards,
> 
> Laurent Pinchart
>