[SETUPLIB][USETUP] Remove the deprecated GenericListHasSingleEntry() function and use instead GetNumberOfListEntries().

- Few FIXMEs get fixed in the process.
- Add some diagnostic ASSERTs.

base/setup/lib/settings.c

@@ -761,10 +761,7 @@ ProcessComputerFiles(
 
     Entry = GetCurrentListEntry(List);
     if (Entry == NULL)
-    {
-        DPRINT("GetCurrentListEntry() failed\n");
         return FALSE;
-    }
 
     RtlStringCchPrintfW(SectionName, ARRAYSIZE(SectionName),
                         L"Files.%s", ((PGENENTRY)GetListEntryData(Entry))->Id);
@@ -794,10 +791,7 @@ ProcessDisplayRegistry(
 
     Entry = GetCurrentListEntry(List);
     if (Entry == NULL)
-    {
-        DPRINT1("GetCurrentListEntry() failed\n");
         return FALSE;
-    }
 
     if (!SetupFindFirstLineW(InfFile, L"Display",
                              ((PGENENTRY)GetListEntryData(Entry))->Id,

base/setup/lib/utils/genlist.c

@@ -88,7 +88,7 @@ SetCurrentListEntry(
     IN PGENERIC_LIST List,
     IN PGENERIC_LIST_ENTRY Entry)
 {
-    if (Entry->List != List)
+    if (!Entry || (Entry->List != List))
         return;
     List->CurrentEntry = Entry;
 }
@@ -143,16 +143,4 @@ GetNumberOfListEntries(
     return List->NumOfEntries;
 }
 
-BOOLEAN
-GenericListHasSingleEntry(
-    IN PGENERIC_LIST List)
-{
-    /*
-     * If both list head pointers (which normally point to the first and last
-     * list member, respectively) point to the same entry then it means that
-     * there is just a single thing in there, otherwise... false!
-     */
-    return (!IsListEmpty(&List->ListHead) && (List->ListHead.Flink == List->ListHead.Blink));
-}
-
 /* EOF */

base/setup/lib/utils/genlist.h

@@ -66,8 +66,4 @@ ULONG
 GetNumberOfListEntries(
     IN PGENERIC_LIST List);
 
-BOOLEAN
-GenericListHasSingleEntry(
-    IN PGENERIC_LIST List);
-
 /* EOF */

base/setup/usetup/genlist.c

@@ -356,17 +356,20 @@ DrawGenericListCurrentItem(
     IN SHORT Left,
     IN SHORT Top)
 {
-    //
-    // FIXME: That stuff crashes when the list is empty!!
-    //
     CHAR CurrentItemText[256];
-    if (GetEntryDescriptionProc)
+
+    if (GetEntryDescriptionProc &&
+        GetNumberOfListEntries(List) > 0)
     {
         GetEntryDescriptionProc(GetCurrentListEntry(List),
                                 CurrentItemText,
                                 ARRAYSIZE(CurrentItemText));
         CONSOLE_SetTextXY(Left, Top, CurrentItemText);
     }
+    else
+    {
+        CONSOLE_SetTextXY(Left, Top, "");
+    }
 }
 
 VOID

base/setup/usetup/usetup.c

@@ -508,9 +508,11 @@ LanguagePage(PINPUT_RECORD Ir)
     SetConsoleCodePage();
     UpdateKBLayout();
 
-    /* If there's just a single language in the list skip
+    /*
-     * the language selection process altogether! */
+     * If there is no language or just a single one in the list,
-    if (GenericListHasSingleEntry(LanguageList))
+     * skip the language selection process altogether.
+     */
+    if (GetNumberOfListEntries(LanguageList) <= 1)
     {
         USetupData.LanguageId = (LANGID)(wcstol(SelectedLanguageId, NULL, 16) & 0xFFFF);
         return WELCOME_PAGE;
@@ -564,9 +566,8 @@ LanguagePage(PINPUT_RECORD Ir)
         }
         else if (Ir->Event.KeyEvent.uChar.AsciiChar == 0x0D)  /* ENTER */
         {
-            //
+            ASSERT(GetNumberOfListEntries(LanguageList) >= 1);
-            // FIXME: That stuff crashes when the list is empty!!
+
-            //
             SelectedLanguageId =
                 ((PGENENTRY)GetListEntryData(GetCurrentListEntry(LanguageList)))->Id;
 
@@ -591,9 +592,8 @@ LanguagePage(PINPUT_RECORD Ir)
 
         if (RefreshPage)
         {
-            //
+            ASSERT(GetNumberOfListEntries(LanguageList) >= 1);
-            // FIXME: That stuff crashes when the list is empty!!
+
-            //
             NewLanguageId =
                 ((PGENENTRY)GetListEntryData(GetCurrentListEntry(LanguageList)))->Id;
 
@@ -897,6 +897,11 @@ UpgradeRepairPage(PINPUT_RECORD Ir)
     NtOsInstallsList = CreateNTOSInstallationsList(PartitionList);
     if (!NtOsInstallsList)
         DPRINT1("Failed to get a list of NTOS installations; continue installation...\n");
+
+    /*
+     * If there is no available installation (or just a single one??) that can
+     * be updated in the list, just continue with the regular installation.
+     */
     if (!NtOsInstallsList || GetNumberOfListEntries(NtOsInstallsList) == 0)
     {
         RepairUpdateFlag = FALSE;
@@ -961,9 +966,8 @@ UpgradeRepairPage(PINPUT_RECORD Ir)
             if (toupper(Ir->Event.KeyEvent.uChar.AsciiChar) == 'U')  /* U */
             {
                 /* Retrieve the current installation */
-                //
+                ASSERT(GetNumberOfListEntries(NtOsInstallsList) >= 1);
-                // FIXME: That stuff crashes when the list is empty!!
+
-                //
                 CurrentInstallation =
                     (PNTOS_INSTALLATION)GetListEntryData(GetCurrentListEntry(NtOsInstallsList));