vim-patch:8.2.3486: illegal memory access with invalid sequence of commands

Problem:    Illegal memory access with invalid sequence of commands.
Solution:   Do not call leave_block() when not in a try block. (closes vim/vim#8966)
            Reset did_emsg so that exception is shown as an error.
https://github.com/vim/vim/commit/cce81e9673fe8d056e8eef310d9919620eccb2f2

Vim9script is N/A, which includes leave_block.

1 files changed, 9 insertions, 3 deletions

diff --git a/src/nvim/ex_eval.c b/src/nvim/ex_eval.c
index b5456e8982..f4aaab5c43 100644
--- a/src/nvim/ex_eval.c
+++ b/src/nvim/ex_eval.c
@@ -1083,7 +1083,7 @@ void ex_endwhile(exarg_T *eap)
   if (cstack->cs_looplevel <= 0 || cstack->cs_idx < 0) {
     eap->errmsg = err;
   } else {
-    fl =  cstack->cs_flags[cstack->cs_idx];
+    fl = cstack->cs_flags[cstack->cs_idx];
     if (!(fl & csf)) {
       // If we are in a ":while" or ":for" but used the wrong endloop
       // command, do not rewind to the next enclosing ":for"/":while".
@@ -1575,6 +1575,7 @@ void ex_endtry(exarg_T *eap)
 
     if (!(cstack->cs_flags[cstack->cs_idx] & CSF_TRY)) {
       eap->errmsg = get_end_emsg(cstack);
+
       // Find the matching ":try" and report what's missing.
       idx = cstack->cs_idx;
       do {
@@ -1594,6 +1595,9 @@ void ex_endtry(exarg_T *eap)
       if (current_exception) {
         discard_current_exception();
       }
+
+      // report eap->errmsg, also when there already was an error
+      did_emsg = false;
     } else {
       idx = cstack->cs_idx;
 
@@ -1664,8 +1668,10 @@ void ex_endtry(exarg_T *eap)
      */
     (void)cleanup_conditionals(cstack, CSF_TRY | CSF_SILENT, TRUE);
 
-    --cstack->cs_idx;
-    --cstack->cs_trylevel;
+    if (cstack->cs_idx >= 0 && (cstack->cs_flags[cstack->cs_idx] & CSF_TRY)) {
+      cstack->cs_idx--;
+    }
+    cstack->cs_trylevel--;
 
     if (!skip) {
       report_resume_pending(pending,