(gettext.info)Special cases

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4.7 Special Cases of Translatable Strings
=========================================

   The attentive reader might now point out that it is not always
possible to mark translatable string with ‘gettext’ or something like
this.  Consider the following case:

     {
       static const char *messages[] = {
         "some very meaningful message",
         "and another one"
       };
       const char *string;
       …
       string
         = index > 1 ? "a default message" : messages[index];

       fputs (string);
       …
     }

   While it is no problem to mark the string ‘"a default message"’ it is
not possible to mark the string initializers for ‘messages’.  What is to
be done?  We have to fulfill two tasks.  First we have to mark the
strings so that the ‘xgettext’ program (Note: xgettext Invocation) can
find them, and second we have to translate the string at runtime before
printing them.

   The first task can be fulfilled by creating a new keyword, which
names a no-op.  For the second we have to mark all access points to a
string from the array.  So one solution can look like this:

     #define gettext_noop(String) String

     {
       static const char *messages[] = {
         gettext_noop ("some very meaningful message"),
         gettext_noop ("and another one")
       };
       const char *string;
       …
       string
         = index > 1 ? gettext ("a default message") : gettext (messages[index]);

       fputs (string);
       …
     }

   Please convince yourself that the string which is written by ‘fputs’
is translated in any case.  How to get ‘xgettext’ know the additional
keyword ‘gettext_noop’ is explained in Note: xgettext Invocation.

   The above is of course not the only solution.  You could also come
along with the following one:

     #define gettext_noop(String) String

     {
       static const char *messages[] = {
         gettext_noop ("some very meaningful message"),
         gettext_noop ("and another one")
       };
       const char *string;
       …
       string
         = index > 1 ? gettext_noop ("a default message") : messages[index];

       fputs (gettext (string));
       …
     }

   But this has a drawback.  The programmer has to take care that he
uses ‘gettext_noop’ for the string ‘"a default message"’.  A use of
‘gettext’ could have in rare cases unpredictable results.

   One advantage is that you need not make control flow analysis to make
sure the output is really translated in any case.  But this analysis is
generally not very difficult.  If it should be in any situation you can
use this second method in this situation.