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=== Gettext integration and interaction with packages

Many packages that support internationalization use the gettext
library. Dependencies for this library are fairly complicated and
therefore, deserve some explanation.

The 'uClibc' C library doesn't implement gettext functionality;
therefore with this C library, a separate gettext must be compiled,
which is provided by the additional +libintl+ library, part of the
+gettext+ package.

On the other hand, the 'glibc' C library does integrate its own
gettext library functions, so it is not necessary to build a separate
+libintl+ library.

However, certain packages need some gettext utilities on the target,
such as the +gettext+ program itself, which allows to retrieve
translated strings, from the command line.

Additionally, some packages (such as +libglib2+) do require gettext
functions unconditionally, while other packages (in general, those who
support +--disable-nls+) only require gettext functions when locale
support is enabled.

Therefore, Buildroot defines two configuration options:

* +BR2_NEEDS_GETTEXT+, which is true as soon as the toolchain doesn't
  provide its own gettext implementation

* +BR2_NEEDS_GETTEXT_IF_LOCALE+, which is true if the toolchain
  doesn't provide its own gettext implementation and if locale support
  is enabled

Packages that need gettext only when locale support is enabled should:

* use +select BR2_PACKAGE_GETTEXT if BR2_NEEDS_GETTEXT_IF_LOCALE+ in the
  +Config.in+ file;

* use +$(if $(BR2_NEEDS_GETTEXT_IF_LOCALE),gettext)+ in the package
  +DEPENDENCIES+ variable in the +.mk+ file.

Packages that unconditionally need gettext (which should be very rare)
should:

* use +select BR2_PACKAGE_GETTEXT if BR2_NEEDS_GETTEXT+ in the +Config.in+
  file;

* use +$(if $(BR2_NEEDS_GETTEXT),gettext)+ in the package
  +DEPENDENCIES+ variable in the +.mk+ file.

Packages that need the +gettext+ utilities on the target (should be
rare) should:

* use +select BR2_PACKAGE_GETTEXT+ in their +Config.in+ file,
  indicating in a comment above that it's a runtime dependency only.

* not add any +gettext+ dependency in the +DEPENDENCIES+ variable of
  their +.mk+ file.