i18n: Skip and warn about textdomain names with a slash (bug #23839)

boost::locale::generator::add_messages_domain() interprets the slash
specially, interpreting everything after it as an encoding name.

It's not clear to me why providing a textdomain with an erroneous name
like this causes Boost.Locale to throw a boost::locale::conv exception
(invalid_charset_error, apparently) when handling t_strings bound to
completely different textdomain, but if we can avoid the issue
altogether then that's good enough.

Made the legacy implementation skip and warn about these names too even
if bindtextdomain(3) says nothing about slashes having a meaning.

changelog

@@ -7,6 +7,8 @@ Version 1.12.4+dev:
        (units misssing fron carryover, units appering twice on map...)
  * Language and i18n:
    * Updated translations: French, Japanese, Latvian
+   * Fixed crashes during start-up on Windows resulting from add-ons containing
+     erroneous textdomain declarations (bug #23839).
  * Multiplayer:
    * Era names no longer support formatting markup in the game setup screen.
    * Made MP lobby filter option filter on eras and mods too (bug #22987).

players_changelog

@@ -5,6 +5,8 @@ changelog: https://github.com/wesnoth/wesnoth/blob/1.12/changelog
 Version 1.12.4+dev:
  * Language and i18n:
    * Updated translations: French, Japanese, Latvian.
+   * Fixed crashes during start-up on Windows resulting from add-ons containing
+     erroneous textdomain declarations (bug #23839).
 
  * User interface:
    * Force uniform font rendering settings across X11 and Apple OS X, avoiding

src/gettext.cpp

@@ -108,6 +108,14 @@ std::string dsngettext (const char * domainname, const char *singular, const cha
 
 void bind_textdomain(const char* domain, const char* directory, const char* encoding)
 {
+	if(domain != NULL && strchr(domain, '/') != NULL) {
+		// For compatibility with Boost.Locale implementation, which interprets
+		// slashes in domain names in a special fashion.
+		ERR_G << "illegal textdomain name '" << domain
+			  << "', skipping textdomain\n";
+		return;
+	}
+
 	if(directory != NULL)
 		bindtextdomain(domain, directory);
 	if(encoding != NULL)

src/gettext_boost.cpp

@@ -96,6 +96,18 @@ namespace
 			{
 				return;
 			}
+
+			if(domain.find('/') != std::string::npos)
+			{
+				// Forward slash has a specific meaning in Boost.Locale domain
+				// names, specifying the encoding. We use UTF-8 for everything
+				// so we can't possibly support that, and odds are it's a user
+				// mistake (as in bug #23839).
+				ERR_G << "illegal textdomain name '" << domain
+					  << "', skipping textdomain\n";
+				return;
+			}
+
 			generator_.add_messages_domain(domain);
 			loaded_domains_.insert(domain);
 		}