feat(aucmd_win): allow crazy things with hidden buffers (#21250)

Problem:    Crash when doing crazy things with hidden buffers.
Solution:   Dynamically allocate the list of autocommand windows.

2 files changed, 5 insertions, 11 deletions

diff --git a/src/nvim/eval/buffer.c b/src/nvim/eval/buffer.c
index 6ebf54ef0f..72eb0f8d67 100644
--- a/src/nvim/eval/buffer.c
+++ b/src/nvim/eval/buffer.c
@@ -86,8 +86,6 @@ static void find_win_for_curbuf(void)
 ///
 /// Information is saved in "cob" and MUST be restored by calling
 /// change_other_buffer_restore().
-///
-/// If this fails then "curbuf" will not be equal to "buf".
 static void change_other_buffer_prepare(cob_T *cob, buf_T *buf)
 {
   CLEAR_POINTER(cob);
@@ -105,9 +103,7 @@ static void change_other_buffer_prepare(cob_T *cob, buf_T *buf)
     // curwin->w_buffer differ from "curbuf", use the autocmd window.
     curbuf = curwin->w_buffer;
     aucmd_prepbuf(&cob->cob_aco, buf);
-    if (curbuf == buf) {
-      cob->cob_using_aco = true;
-    }
+    cob->cob_using_aco = true;
   }
 }
 
diff --git a/src/nvim/eval/vars.c b/src/nvim/eval/vars.c
index f002071ad2..d37631af8c 100644
--- a/src/nvim/eval/vars.c
+++ b/src/nvim/eval/vars.c
@@ -1802,13 +1802,11 @@ void f_setbufvar(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
       // Set curbuf to be our buf, temporarily.
       aucmd_prepbuf(&aco, buf);
-      if (curbuf == buf) {
-        // Only when it worked to set "curbuf".
-        set_option_from_tv(varname + 1, varp);
 
-        // reset notion of buffer
-        aucmd_restbuf(&aco);
-      }
+      set_option_from_tv(varname + 1, varp);
+
+      // reset notion of buffer
+      aucmd_restbuf(&aco);
     } else {
       const size_t varname_len = strlen(varname);
       char *const bufvarname = xmalloc(varname_len + 3);