From f8c8a245aa5bdfc2092f7e910a2d4ce798cd188e Mon Sep 17 00:00:00 2001
From: bfredl <bjorn.linse@gmail.com>
Date: Tue, 7 Jan 2025 11:16:53 +0100
Subject: [PATCH] fix(terminal): don't crash on unprintable chars

fixes #31897
---
 src/nvim/vterm/screen.c                  |  2 +-
 test/functional/terminal/buffer_spec.lua | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/nvim/vterm/screen.c b/src/nvim/vterm/screen.c
index f24e47e543..c91c6fb84f 100644
--- a/src/nvim/vterm/screen.c
+++ b/src/nvim/vterm/screen.c
@@ -909,7 +909,7 @@ int vterm_screen_get_cell(const VTermScreen *screen, VTermPos pos, VTermScreenCe
     return 0;
   }
 
-  cell->schar = intcell->schar;
+  cell->schar = (intcell->schar == (uint32_t)-1) ? 0 : intcell->schar;
 
   cell->attrs.bold = intcell->pen.bold;
   cell->attrs.underline = intcell->pen.underline;
diff --git a/test/functional/terminal/buffer_spec.lua b/test/functional/terminal/buffer_spec.lua
index b6de687af9..cc807ba555 100644
--- a/test/functional/terminal/buffer_spec.lua
+++ b/test/functional/terminal/buffer_spec.lua
@@ -435,6 +435,19 @@ describe(':terminal buffer', function()
     ]])
   end)
 
+  it('handles unprintable chars', function()
+    local screen = Screen.new(50, 7)
+    feed 'i'
+    local chan = api.nvim_open_term(0, {})
+    api.nvim_chan_send(chan, '\239\187\191') -- '\xef\xbb\xbf'
+    screen:expect([[
+      {18:<feff>}^                                            |
+                                                        |*5
+      {5:-- TERMINAL --}                                    |
+    ]])
+    eq('\239\187\191', api.nvim_get_current_line())
+  end)
+
   it("handles bell respecting 'belloff' and 'visualbell'", function()
     local screen = Screen.new(50, 7)
     local chan = api.nvim_open_term(0, {})