gettext.h: include <locale> before defining the gettext macro (#4452)

Fixes #4446: a syntax error that happens if something else (such as
<iomanip> or <locale> in certain libstdc++ versions) includes
<libintl.h> later, which contains a function declaration for gettext
that gets mangled by the macro.

See the added comment in gettext.h and the discussion in #4446/#4452
for details.

diff --git a/src/gettext.h b/src/gettext.h
index b8d27f77ceb82a2b229ba8e01b24b4baf461a0cd..885d7ca2da165691cf5e1c38a2394b175cd26d87 100644 (file)
--- a/src/gettext.h
+++ b/src/gettext.h
@@ -25,6 +25,16 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #if USE_GETTEXT
        #include <libintl.h>
 #else
+       // In certain environments, some standard headers like <iomanip>
+       // and <locale> include libintl.h. If libintl.h is included after
+       // we define our gettext macro below, this causes a syntax error
+       // at the declaration of the gettext function in libintl.h.
+       // Fix this by including such a header before defining the macro.
+       // See issue #4446.
+       // Note that we can't include libintl.h directly since we're in
+       // the USE_GETTEXT=0 case and can't assume that gettext is installed.
+       #include <locale>
+
        #define gettext(String) String
 #endif