From 99de8a6dcdc81bbeb70296704b8c82029e363de2 Mon Sep 17 00:00:00 2001
From: Mounir IDRASSI <mounir.idrassi@idrix.fr>
Date: Thu, 28 Apr 2016 10:36:04 +0200
Subject: Windows: Only use A: and B: for mounting when no other free drive
 letter available or when explicitly chosen by user. This avoid side effects
 when mounting volumes as removable media and automatic drive selection (e.g.
 A: become invisible in explorer after closing all explorer instances although
 it is still mounted).

---
 src/Common/Dlgcode.c |  8 +++++---
 src/Mount/Mount.c    | 31 ++++++++++++++++++++++++++++++-
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/src/Common/Dlgcode.c b/src/Common/Dlgcode.c
index 77210029..6958afe9 100644
--- a/src/Common/Dlgcode.c
+++ b/src/Common/Dlgcode.c
@@ -6760,11 +6760,13 @@ DWORD GetUsedLogicalDrives (void)
 int GetFirstAvailableDrive ()
 {
 	DWORD dwUsedDrives = GetUsedLogicalDrives();
-	int i;
+	int i, drive;
 
-	for (i = 0; i < 26; i++)
+	/* let A: and B: be used as last resort since they can introduce side effects */
+	for (i = 2; i < 28; i++)
 	{
-		if (!(dwUsedDrives & 1 << i))
+		drive = (i < 26) ? i : (i - 26);
+		if (!(dwUsedDrives & 1 << drive))
 			return i;
 	}
 
diff --git a/src/Mount/Mount.c b/src/Mount/Mount.c
index 9619a9f6..1851af06 100644
--- a/src/Mount/Mount.c
+++ b/src/Mount/Mount.c
@@ -5075,6 +5075,7 @@ static BOOL MountAllDevicesThreadCode (HWND hwndDlg, BOOL bPasswordPrompt)
 				if (!mounted)
 				{	
 					int nDosDriveNo;
+					int driveAItem = -1, driveBItem = -1;
 
 					while (LOWORD (GetItemLong (driveList, selDrive)) != 0xffff)
 					{
@@ -5084,11 +5085,39 @@ static BOOL MountAllDevicesThreadCode (HWND hwndDlg, BOOL bPasswordPrompt)
 							continue;
 						}
 						nDosDriveNo = HIWORD(GetItemLong (driveList, selDrive)) - L'A';
+
+						/* don't use drives A: and B: for now until no other free drive found */
+						if (nDosDriveNo == 0)
+						{
+							driveAItem = selDrive;
+							selDrive++;							
+							continue;
+						}
+						if (nDosDriveNo == 1)
+						{
+							driveBItem = selDrive;
+							selDrive++;
+							continue;
+						}
 						break;
 					}
 
 					if (LOWORD (GetItemLong (driveList, selDrive)) == 0xffff)
-						goto ret;
+					{
+						/* use A: or B: if available as a last resort */
+						if (driveAItem >= 0)
+						{
+							nDosDriveNo = 0;
+							selDrive = driveAItem;
+						}
+						else if (driveBItem >= 0)
+						{
+							nDosDriveNo = 1;
+							selDrive = driveBItem;
+						}
+						else
+							goto ret;
+					}
 
 					// First try user password then cached passwords
 					if ((mounted = MountVolume (hwndDlg, nDosDriveNo, szFileName, &VolumePassword, VolumePkcs5, VolumePim, VolumeTrueCryptMode, bCacheInDriver, bIncludePimInCache, bForceMount, &mountOptions, TRUE, FALSE)) > 0
-- 
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