From ad6987e1b102611528ee139cd4b07b2f06866e06 Mon Sep 17 00:00:00 2001
From: Lars Brinkhoff <lars@nocrew.org>
Date: Tue, 18 Feb 2020 15:16:26 +0100
Subject: [PATCH] New backend flag for needing a terminal.

---
 putty.h            | 1 +
 unix/uxplink.c     | 6 ++++++
 windows/winplink.c | 6 ++++++
 3 files changed, 13 insertions(+)

diff --git a/putty.h b/putty.h
index abfb060f..298ad775 100644
--- a/putty.h
+++ b/putty.h
@@ -482,6 +482,7 @@ enum {
 /* Backend flags */
 #define BACKEND_RESIZE_FORBIDDEN    0x01   /* Backend does not allow
                                               resizing terminal */
+#define BACKEND_NEEDS_TERMINAL      0x02   /* Backend must have terminal */
 
 struct Backend {
     const BackendVtable *vt;
diff --git a/unix/uxplink.c b/unix/uxplink.c
index 473a0c4b..57b84af8 100644
--- a/unix/uxplink.c
+++ b/unix/uxplink.c
@@ -820,6 +820,12 @@ int main(int argc, char **argv)
         return 1;
     }
 
+    if (backvt->flags & BACKEND_NEEDS_TERMINAL) {
+        fprintf(stderr,
+                "Plink must have a terminal to run.\n");
+        return 1;
+    }
+
     /*
      * Block SIGPIPE, so that we'll get EPIPE individually on
      * particular network connections that go wrong.
diff --git a/windows/winplink.c b/windows/winplink.c
index 304e4873..45a34688 100644
--- a/windows/winplink.c
+++ b/windows/winplink.c
@@ -393,6 +393,12 @@ int main(int argc, char **argv)
         return 1;
     }
 
+    if (vt->flags & BACKEND_NEEDS_TERMINAL) {
+        fprintf(stderr,
+                "Plink must have a terminal to run.\n");
+        return 1;
+    }
+
     sk_init();
     if (p_WSAEventSelect == NULL) {
         fprintf(stderr, "Plink requires WinSock 2\n");