From d7e71357dc01fd62eec0a7ece04c76cdd643e822 Mon Sep 17 00:00:00 2001
From: James Woodcock <james_woodcock@yahoo.co.uk>
Date: Fri, 27 Apr 2018 16:15:38 +0100
Subject: [PATCH] [CMD] Fix CTRL-C handling.

Using CTRL-C to cancel command line input would leave the prompt in
a state where the next command would be ignored.  For example:

dir<CTRL-C>
dir

would cause cmd.exe to ignore the second dir command.
---
 base/shell/cmd/cmd.c      | 11 +++++++++--
 base/shell/cmd/cmd.h      |  2 +-
 base/shell/cmd/cmdinput.c | 17 ++++++++++++++---
 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/base/shell/cmd/cmd.c b/base/shell/cmd/cmd.c
index 89a2b1b6996..90dc6f1806c 100644
--- a/base/shell/cmd/cmd.c
+++ b/base/shell/cmd/cmd.c
@@ -151,7 +151,7 @@ typedef NTSTATUS (WINAPI *NtReadVirtualMemoryProc)(HANDLE, PVOID, PVOID, ULONG,
 
 BOOL bExit = FALSE;       /* indicates EXIT was typed */
 BOOL bCanExit = TRUE;     /* indicates if this shell is exitable */
-BOOL bCtrlBreak = FALSE;  /* Ctrl-Break or Ctrl-C hit */
+volatile BOOL bCtrlBreak = FALSE;  /* Ctrl-Break or Ctrl-C hit */
 BOOL bIgnoreEcho = FALSE; /* Set this to TRUE to prevent a newline, when executing a command */
 static BOOL bWaitForCommand = FALSE; /* When we are executing something passed on the commandline after /c or /k */
 INT  nErrorLevel = 0;     /* Errorlevel of last launched external program */
@@ -1423,6 +1423,12 @@ ReadLine(TCHAR *commandline, BOOL bMore)
             ConOutChar(_T('\n'));
             return FALSE;
         }
+
+        if (readline[0] == L'\0')
+        {
+            return FALSE;
+        }
+
         ip = readline;
     }
     else
@@ -1476,6 +1482,8 @@ BOOL WINAPI BreakHandler(DWORD dwCtrlType)
         LeaveCriticalSection(&ChildProcessRunningLock);
     }
 
+    bCtrlBreak = TRUE;
+
     rec.EventType = KEY_EVENT;
     rec.Event.KeyEvent.bKeyDown = TRUE;
     rec.Event.KeyEvent.wRepeatCount = 1;
@@ -1490,7 +1498,6 @@ BOOL WINAPI BreakHandler(DWORD dwCtrlType)
                       1,
                       &dwWritten);
 
-    bCtrlBreak = TRUE;
     /* FIXME: Handle batch files */
 
     //ConOutPrintf(_T("^C"));
diff --git a/base/shell/cmd/cmd.h b/base/shell/cmd/cmd.h
index 6a2f680a68f..285916c74c7 100644
--- a/base/shell/cmd/cmd.h
+++ b/base/shell/cmd/cmd.h
@@ -47,7 +47,7 @@
 extern LPTSTR lpOriginalEnvironment;
 extern WORD   wColor;
 extern WORD   wDefColor;
-extern BOOL   bCtrlBreak;
+extern volatile BOOL   bCtrlBreak;
 extern BOOL   bIgnoreEcho;
 extern BOOL   bExit;
 extern BOOL   bDisableBatchEcho;
diff --git a/base/shell/cmd/cmdinput.c b/base/shell/cmd/cmdinput.c
index 5276d0d8afa..09e58536086 100644
--- a/base/shell/cmd/cmdinput.c
+++ b/base/shell/cmd/cmdinput.c
@@ -450,12 +450,23 @@ BOOL ReadCommand(LPTSTR str, INT maxlen)
                 break;
 
             case _T('C'):
-                bCharInput = TRUE;
-                if (!(ir.Event.KeyEvent.dwControlKeyState &
+                if ((ir.Event.KeyEvent.dwControlKeyState &
                     (RIGHT_CTRL_PRESSED|LEFT_CTRL_PRESSED)))
                 {
-                    break;
+                    /* A CTRL-C.  Don't clear the the command line,
+                     * but return an empty string in str. */
+                    str[0] = L'\0';
+                    curx = orgx;
+                    cury = orgy;
+                    current = charcount = 0;
+                    bReturn = TRUE;
                 }
+                else
+                {
+                    /* Just a normal 'C' character */
+                    bCharInput = TRUE;
+                }
+                break;
 
             case VK_RETURN:
                 /* end input, return to main */