Use "system" for "use system language", and don't try to print a null string.

Add a #define USE_SYSTEM_LANGUAGE for the language string meaning "use
the system setting", and use that instead of hardcoding "system" in
various places.

If "language" is null, don't try to write it to the file with fprintf()
- on *most* systems, that prints "(null)", but on some systems, such as
Solaris, it *crashes*.  Write USE_SYSTEM_LANGUAGE instead.  Check for
"(null)" and treat it as meaning "use the system language".

Map "auto" to "use the system language" as well, for backwards
compatibility.

Change-Id: Iba9be540a5139e9cca8bddd0761ee4cbf0f79a49
Reviewed-on: https://code.wireshark.org/review/15147
Reviewed-by: Guy Harris <guy@alum.mit.edu>

4 files changed, 19 insertions, 5 deletions

diff --git a/ui/language.c b/ui/language.c
index 65a338011e..2bc721aafa 100644
--- a/ui/language.c
+++ b/ui/language.c
@@ -48,8 +48,19 @@ read_language_pref(gchar *key, const gchar *value,
     if (strcmp(key, LANGUAGE_PREF_LANGUAGE) == 0) {
         if (language)
             g_free(language);
-        if (!value || !*value)
-            language = g_strdup("auto");
+        /*
+         * For backwards compatibility, treat "auto" as meaning "use the
+         * system language".
+         *
+         * To handle the old buggy code that didn't check whether "language"
+         * was null before trying to print it, treat "(null)" - which many,
+         * but *NOT* all, system printfs print for a null pointer (some
+         * printfs, such as the one in Solaris, *crash* with %s and a null
+         * pointer) - as meaning "use the system language".
+         */
+        if (!value || !*value || strcmp(value, "auto") == 0 ||
+            strcmp(value, "(null)") == 0)
+            language = g_strdup(USE_SYSTEM_LANGUAGE);
         else
             language = g_strdup(value);
     }
@@ -113,7 +124,7 @@ write_language_prefs(void)
         "# So be careful, if you want to make manual changes here.\n"
         "\n", rf);
 
-    fprintf(rf, LANGUAGE_PREF_LANGUAGE ": %s\n", language);
+    fprintf(rf, LANGUAGE_PREF_LANGUAGE ": %s\n", language ? language : USE_SYSTEM_LANGUAGE);
 
     fclose(rf);
 
diff --git a/ui/language.h b/ui/language.h
index 8b94d23f69..988461befc 100644
--- a/ui/language.h
+++ b/ui/language.h
@@ -28,6 +28,8 @@
 extern "C" {
 #endif /* __cplusplus */
 
+#define USE_SYSTEM_LANGUAGE	"system"
+
 extern char *language;
 
 extern void  read_language_prefs(void);
diff --git a/ui/qt/main_window_preferences_frame.cpp b/ui/qt/main_window_preferences_frame.cpp
index b876ff3d4f..b3927c594e 100644
--- a/ui/qt/main_window_preferences_frame.cpp
+++ b/ui/qt/main_window_preferences_frame.cpp
@@ -96,7 +96,7 @@ MainWindowPreferencesFrame::MainWindowPreferencesFrame(QWidget *parent) :
         ui->languageComboBox->addItem(ico, lang, locale);
     }
 
-    ui->languageComboBox->setItemData(0, "system");
+    ui->languageComboBox->setItemData(0, USE_SYSTEM_LANGUAGE);
     ui->languageComboBox->model()->sort(0);
 
     for (int i = 0; i < ui->languageComboBox->count(); i += 1) {
diff --git a/ui/qt/wireshark_application.cpp b/ui/qt/wireshark_application.cpp
index eeade6438c..523907555e 100644
--- a/ui/qt/wireshark_application.cpp
+++ b/ui/qt/wireshark_application.cpp
@@ -43,6 +43,7 @@
 #include "ui/decode_as_utils.h"
 #include "ui/preference_utils.h"
 #include "ui/iface_lists.h"
+#include "ui/language.h"
 #include "ui/recent.h"
 #include "ui/simple_dialog.h"
 #include "ui/util.h"
@@ -1055,7 +1056,7 @@ void WiresharkApplication::loadLanguage(const QString& newLanguage)
     QLocale locale;
     QString localeLanguage;
 
-    if (newLanguage.isEmpty() || newLanguage == "system") {
+    if (newLanguage.isEmpty() || newLanguage == USE_SYSTEM_LANGUAGE) {
         localeLanguage = QLocale::system().name();
     } else {
         localeLanguage = newLanguage;