vim-patch:9.0.0389: crash when 'tagfunc' closes the window

Problem:    Crash when 'tagfunc' closes the window.
Solution:   Bail out when the window was closed.

https://github.com/vim/vim/commit/ccfde4d028e891a41e3548323c3d47b06fb0b83e

Add docs for E1299 from Vim runtime.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/nvim/tag.c b/src/nvim/tag.c
index 5216919d98..16d6629c2e 100644
--- a/src/nvim/tag.c
+++ b/src/nvim/tag.c
@@ -106,6 +106,8 @@ static char_u *recurmsg
   = (char_u *)N_("E986: cannot modify the tag stack within tagfunc");
 static char_u *tfu_inv_ret_msg
   = (char_u *)N_("E987: invalid return value from tagfunc");
+static char e_window_unexpectedly_close_while_searching_for_tags[]
+  = N_("E1299: Window unexpectedly closed while searching for tags");
 
 static char *tagmatchname = NULL;   // name of last used tag
 
@@ -501,6 +503,15 @@ void do_tag(char *tag, int type, int count, int forceit, int verbose)
                                    // found: all matches found.
       }
 
+      // A tag function may do anything, which may cause various
+      // information to become invalid.  At least check for the tagstack
+      // to still be the same.
+      if (tagstack != curwin->w_tagstack) {
+        emsg(_(e_window_unexpectedly_close_while_searching_for_tags));
+        FreeWild(new_num_matches, new_matches);
+        break;
+      }
+
       // If there already were some matches for the same name, move them
       // to the start.  Avoids that the order changes when using
       // ":tnext" and jumping to another file.