[PATCH v2] Document the internal _ and N_ macros

[Carlos O'Donell]

On 5/6/20 11:26 AM, Florian Weimer wrote:
> -----
> Changes in v2: Incorporate suggestion from Carlos.

OK for master.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
 
>  include/libintl.h | 32 ++++++++++++++++++++++++--------
>  1 file changed, 24 insertions(+), 8 deletions(-)
> 
> diff --git a/include/libintl.h b/include/libintl.h
> index 9a11367ec6..3d63b7abbd 100644
> --- a/include/libintl.h
> +++ b/include/libintl.h
> @@ -37,17 +37,33 @@ extern char *__bind_textdomain_codeset (const char *__domainname,
>  extern const char _libc_intl_domainname[];
>  libc_hidden_proto (_libc_intl_domainname)
>  
> -/* Define the macros `_' and `N_' for conveniently marking translatable
> -   strings in the libc source code.  We have to make sure we get the
> -   correct definitions so we undefine the macros first.  */
> +/* _ marks its argument, a string literal, for translation, and
> +   performs translation at run time if the LC_MESSAGES locale category
> +   has been set.  The MSGID argument is extracted, added to the
> +   translation database, and eventually submitted to the translation
> +   team for processing.  New translations are periodically
> +   incorporated into the glibc source tree as part of translation
> +   updates.  */
> +# undef _
> +# define _(msgid) __dcgettext (_libc_intl_domainname, msgid, LC_MESSAGES)
>  
> +/* N_ marks its argument, a string literal, for translation, so that
> +   it is extracted and added to the translation database (similar to
> +   the _ macro above).  It does not translate the string at run time.
> +   The first, primary use case for N_ is a context in which a string
> +   literal is required, such as an initializer.  Translation will
> +   happen later, for example using the __gettext function.
> +
> +   The second, historic, use case involves strings which may be
> +   translated in a future version of the library, but cannot be
> +   translated in current releases due to some technical limitation
> +   (e.g., gettext not being available in the dynamic loader).  No
> +   translation at run time happens in such cases.  In the future, this
> +   historic usage of N_ may become deprecated.  Strings which are not
> +   translated create unnecessary work for the translation team.  We
> +   continue to use N_ because it helps mark translatable strings.  */
>  # undef N_
>  # define N_(msgid)	msgid
>  
> -# undef _
> -/* This is defined as an optimizing macro, so use it.  */
> -# define _(msgid) \
> -  __dcgettext (_libc_intl_domainname, msgid, LC_MESSAGES)
> -
>  # endif /* !_ISOMAC */
>  #endif
> 


-- 
Cheers,
Carlos.