crash when cmdheight=0 and :intro is executed

[omar25h]

Problem

Neovim crashes when cmdheight=0 and the :intro command is executed. This does not happen when cmdheight is set to any positive number

Assertion failed: (to_scroll >= 0), function msg_scroll_flush, file message.c, line 2345.

Steps to reproduce

nvim --clean
:set cmdheight=0
:intro

Expected behavior

Intro is shown and nvim does not crash

Neovim version (nvim -v)

NVIM v0.10.0-dev-1801+g2ebd328a7

Vim (not Nvim) behaves the same?

no

Operating system/version

macOS 14.1.2

Terminal name/version

Wezterm

$TERM environment variable

wezterm

Installation

bob

[glepnir]

I can reproduce. not sure this is correct.

-    assert(to_scroll >= 0);
+    if (p_ch > 0) {
+      assert(to_scroll >= 0);
+    }

[zeertzjq]

Bisected to 3a7cb72

[zeertzjq]

This seems to fix the problem:

diff --git a/src/nvim/version.c b/src/nvim/version.c
index 2caf2c0cb..470e0b421 100644
--- a/src/nvim/version.c
+++ b/src/nvim/version.c
@@ -2831,6 +2831,11 @@ void intro_message(int colon)
       }
     }
   }
+
+  // Make the wait-return message appear just below the text.
+  if (colon) {
+    msg_row = row;
+  }
 }
 
 static void do_intro_line(int row, char *mesg, int attr)

[zeertzjq]

Fixed by #28343