libcompat: Define gettext context functions when NLS is disabled

When the package is configured with NLS disabled (--disable-nls),
the build will fail due to undefined references to LC_MESSAGES, the
gettext.h header file does not correctly handle the gettext context
related function declarations on disabled NLS support, which is known
to be used by downstreams. This adds all missing macros corresponding
to their NLS enabled counterparts.

debian/changelog

@@ -30,6 +30,7 @@ dpkg (1.16.0) UNRELEASED; urgency=low
     packages are not-installed or half-installed.
   * By default reject installing packages w/o an Architecture field. They
     now need --force-architecture, dpkg will still warn about them though.
+  * Fix build failure when passing --disable-nls to configure.
 
   [ Raphaël Hertzog ]
   * Fail properly when debian/source/format is empty. Closes: #600854

lib/compat/gettext.h

@@ -96,6 +96,8 @@
 /* The separator between msgctxt and msgid in a .mo file.  */
 #define GETTEXT_CONTEXT_GLUE "\004"
 
+#if ENABLE_NLS
+
 /* Pseudo function calls, taking a MSGCTXT and a MSGID instead of just a
    MSGID.  MSGCTXT and MSGID must be string literals.  MSGCTXT should be
    short and rarely need to change.
@@ -268,4 +270,34 @@ dcnpgettext_expr (const char *domain,
   return (n == 1 ? msgid : msgid_plural);
 }
 
+#else /* ENABLE_NLS */
+
+#define pgettext(Msgctxt, Msgid) ((void) (Msgctxt), gettext (Msgid))
+#define dpgettext(Domainname, Msgctxt, Msgid) \
+  ((void) (Domainname), pgettext (Msgctxt, Msgid))
+#define dcpgettext(Domainname, Msgctxt, Msgid, Category) \
+  ((void) (Category), dpgettext (Domainname, Msgctxt, Msgid))
+
+#define npgettext(Msgctxt, Msgid, MsgidPlural, N) \
+  ((void) (Msgctxt), ngettext (Msgid, MsgidPlural, N))
+#define dnpgettext(Domainname, Msgctxt, Msgid, MsgidPlural, N) \
+  ((void) (Domainname), npgettext (Msgctxt, Msgid, MsgidPlural, N)
+#define dcnpgettext(Domainname, Msgctxt, Msgid, MsgidPlural, N, Category) \
+   ((void) (Category), dnpgettext (Domainname, Msgctxt, Msgid, MsgidPlural, N)
+
+#define pgettext_expr(Msgctxt, Msgid) pgettext (Msgctxt, Msgid)
+#define dpgettext_expr(Domainname, Msgctxt, Msgid) \
+  dpgettext (Domainname, Msgctxt, Msgid)
+#define dcpgettext_expr(Domainname, Msgctxt, Msgid, Category) \
+  dcpgettext (Domainname, Msgctxt, Msgid, Category)
+
+#define npgettext_expr(Msgctxt, Msgid, MsgidPlural, N) \
+  npgettext (Msgctxt, Msgid, MsgidPlural, N)
+#define dnpgettext_expr(Domainname, Msgctxt, Msgid, MsgidPlural, N) \
+  dnpgettext (Domainname, Msgctxt, Msgid, MsgidPlural, N)
+#define dcnpgettext_expr(Domainname, Msgctxt, Msgid, MsgidPlural, N, Category) \
+  dcnpgettext (Domainname, Msgctxt, Msgid, MsgidPlural, N, Category)
+
+#endif /* ENABLE_NLS */
+
 #endif /* _LIBGETTEXT_H */