Fl_Preferences (X11): Fix detection of preferences directory

- Fix compiler warning [-Wmaybe-uninitialized] for variable home
- Reformat enum 'Root' for better readability
- Add new enum values CORE_SYSTEM_L and CORE_USER_L
- Improve documentation (deprecated and new enums)
- Initialize internal static variable 'filename' which could be used
  uninitialized and thus return any previous value (type == MEMORY)

2 files changed, 33 insertions, 25 deletions

diff --git a/FL/Fl_Preferences.H b/FL/Fl_Preferences.H
index 82f3ef47d..612827a90 100644
--- a/FL/Fl_Preferences.H
+++ b/FL/Fl_Preferences.H
@@ -121,17 +121,20 @@ public:
      Define the scope of the preferences.
    */
   enum Root {
-    UNKNOWN_ROOT_TYPE = -1, ///< Returned if storage could not be determined.
-    SYSTEM = 0,        ///< Preferences are used system-wide, deprecated, see SYSTEM_L
-    USER,              ///< Preferences apply only to the current user, deprecated, see USER_L
-    MEMORY,            ///< Returned if querying memory mapped preferences
-    ROOT_MASK = 0xFF,  ///< masks for the values above
-    CORE = 0x100,      ///< OR'd by FLTK to read and write core library preferences and options
-    CORE_SYSTEM = CORE|SYSTEM,
-    CORE_USER = CORE|USER,
-    C_LOCALE = 0x1000, ///< this flag should always be set, it makes sure that floating point values wre writte correctly independently of the current locale
-    SYSTEM_L = SYSTEM|C_LOCALE, ///< Preferences are used system-wide, locale independent
-    USER_L = USER|C_LOCALE,     ///< Preferences apply only to the current user, locale independent
+    UNKNOWN_ROOT_TYPE = -1,            ///< Returned if storage could not be determined.
+    SYSTEM            =  0,            ///< Preferences are used system-wide, deprecated, see SYSTEM_L
+    USER,                              ///< Preferences apply only to the current user, deprecated, see USER_L
+    MEMORY,                            ///< Returned if querying memory mapped preferences
+    ROOT_MASK     = 0x00FF,            ///< mask for the values above
+    CORE          = 0x0100,            ///< OR'd by FLTK to read and write core library preferences and options
+    C_LOCALE      = 0x1000,            ///< this flag should always be set, it makes sure that floating point
+                                       ///< values are written correctly independently of the current locale
+    SYSTEM_L      = SYSTEM | C_LOCALE, ///< Preferences are used system-wide, locale independent
+    USER_L        = USER | C_LOCALE,   ///< Preferences apply only to the current user, locale independent
+    CORE_SYSTEM_L = CORE | SYSTEM_L,   ///< same as CORE | SYSTEM | C_LOCALE
+    CORE_USER_L   = CORE | USER_L,     ///< same as CORE | USER | C_LOCALE
+    CORE_SYSTEM   = CORE | SYSTEM,     ///< deprecated, same as CORE | SYSTEM
+    CORE_USER     = CORE | USER,       ///< deprecated, same as CORE | USER
   };
 
   /**
diff --git a/src/drivers/X11/Fl_X11_System_Driver.cxx b/src/drivers/X11/Fl_X11_System_Driver.cxx
index 64cac3779..e62fdf8b8 100644
--- a/src/drivers/X11/Fl_X11_System_Driver.cxx
+++ b/src/drivers/X11/Fl_X11_System_Driver.cxx
@@ -455,32 +455,37 @@ void Fl_X11_System_Driver::newUUID(char *uuidBuffer)
 /*
  Note: `prefs` can be NULL!
  */
-char *Fl_X11_System_Driver::preference_rootnode(Fl_Preferences * /*prefs*/, Fl_Preferences::Root root, const char *vendor,
+char *Fl_X11_System_Driver::preference_rootnode(Fl_Preferences * /*prefs*/,
+                                                Fl_Preferences::Root root,
+                                                const char *vendor,
                                                 const char *application)
 {
   static char *filename = 0L;
   if (!filename) filename = (char*)::calloc(1, FL_PATH_MAX);
-  const char *home;
-  switch (root&Fl_Preferences::ROOT_MASK) {
+  const char *home = "";
+  int pref_type = root & Fl_Preferences::ROOT_MASK;
+  switch (pref_type) {
     case Fl_Preferences::USER:
       home = getenv("HOME");
       // make sure that $HOME is set to an existing directory
-      if ( (home==NULL) || (home[0]==0) || (::access(home, F_OK)==-1) ) {
+      if ((home == NULL) || (home[0] == 0) || (::access(home, F_OK) == -1)) {
         struct passwd *pw = getpwuid(getuid());
-        home = pw->pw_dir;
+        if (pw)
+          home = pw->pw_dir;
       }
-      if ( (home==0L) || (home[0]==0) || (::access(home, F_OK)==-1) ) {
+      if ((home == 0L) || (home[0] == 0) || (::access(home, F_OK) == -1))
         return NULL;
-      } else {
-        strlcpy(filename, home, FL_PATH_MAX);
-        if (filename[strlen(filename)-1] != '/')
-          strlcat(filename, "/", FL_PATH_MAX);
-        strlcat(filename, ".fltk/", FL_PATH_MAX);
-      }
+      strlcpy(filename, home, FL_PATH_MAX);
+      if (filename[strlen(filename) - 1] != '/')
+        strlcat(filename, "/", FL_PATH_MAX);
+      strlcat(filename, ".fltk/", FL_PATH_MAX);
       break;
     case Fl_Preferences::SYSTEM:
       strcpy(filename, "/etc/fltk/");
       break;
+    default:              // MEMORY
+      filename[0] = '\0'; // empty string
+      break;
   }
 
   // Make sure that the parameters are not NULL
@@ -492,8 +497,8 @@ char *Fl_X11_System_Driver::preference_rootnode(Fl_Preferences * /*prefs*/, Fl_P
   snprintf(filename + strlen(filename), FL_PATH_MAX - strlen(filename),
            "%s/%s.prefs", vendor, application);
 
-  // If this is the SYSTEM path, we are done
-  if ((root&Fl_Preferences::ROOT_MASK)!=Fl_Preferences::USER)
+  // If this is not the USER path (i.e. SYSTEM or MEMORY), we are done
+  if ((pref_type) != Fl_Preferences::USER)
     return filename;
 
   // If the legacy file exists, we are also done