[PATCH v2] msvcrt: gets() should handle EOF on stdin gracefully

[James Woodcock]

Fixes https://bugs.winehq.org/show_bug.cgi?id=44550

gets() and getws() should return NULL when STDIN is closed and the
input buffer is empty.

Tested on Ubuntu 17.10.

Signed-off-by: James Woodcock 
---
 dlls/msvcrt/file.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/dlls/msvcrt/file.c b/dlls/msvcrt/file.c
index 7022e48b19..f36780ba97 100644
--- a/dlls/msvcrt/file.c
+++ b/dlls/msvcrt/file.c
@@ -4719,6 +4719,14 @@ char * CDECL MSVCRT_gets(char *buf)
       if(cc != '\r')
           *buf++ = (char)cc;
   }
+
+  if ((cc == MSVCRT_EOF) && (buf_start == buf)) /* If nothing read, return 0*/
+  {
+    TRACE(":nothing read\n");
+    MSVCRT__unlock_file(MSVCRT_stdin);
+    return NULL;
+  }
+
   *buf = '\0';

TRACE("got '%s'\n", buf_start);
@@ -4741,6 +4749,14 @@ MSVCRT_wchar_t* CDECL MSVCRT__getws(MSVCRT_wchar_t* buf)
         if (cc != '\r')
             *buf++ = (MSVCRT_wchar_t)cc;
     }
+
+    if ((cc == MSVCRT_WEOF) && (ws == buf)) /* If nothing read, return 0*/
+    {
+      TRACE(":nothing read\n");
+      MSVCRT__unlock_file(MSVCRT_stdin);
+      return NULL;
+    }
+
     *buf = '\0';

TRACE("got %s\n", debugstr_w(ws));