Bug #29469: Client dies if a query is issued after hitting Ctrl + C

The Ctrl-C handler in mysql closes the console while ReadConsole()
waits for console input.
But the main thread was detecting that ReadConsole() haven't read 
anything and was processing as if there're data in the buffer.
Fixed to handle correctly this error condition.
No test case added as the test relies on Ctrl-C sent to the client
from its console.

1 files changed, 5 insertions, 2 deletions

diff --git a/mysys/my_conio.c b/mysys/my_conio.c
index 23b0c55e7a9..def15674f26 100644
--- a/mysys/my_conio.c
+++ b/mysys/my_conio.c
@@ -184,16 +184,19 @@ char* my_cgets(char *buffer, unsigned long clen, unsigned long* plen)
   }
   while (GetLastError() == ERROR_NOT_ENOUGH_MEMORY);
 
+  /* We go here on error reading the string (Ctrl-C for example) */
+  if (!*plen)
+    result= NULL;                              /* purecov: inspected */
 
   if (result != NULL)
   {
-    if (buffer[*plen - 2] == '\r')
+    if (*plen > 1 && buffer[*plen - 2] == '\r')
     {
       *plen= *plen - 2;
     }
     else 
     {
-      if (buffer[*plen - 1] == '\r')
+      if (*plen > 0 && buffer[*plen - 1] == '\r')
       {
         char tmp[3];
         int  tmplen= sizeof(tmp);