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 #8966)
            Reset did_emsg so that exception is shown as an error.

src/ex_eval.c

@@ -1385,7 +1385,7 @@ ex_endwhile(exarg_T *eap)
 	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
@@ -2007,6 +2007,7 @@ 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
@@ -2025,6 +2026,9 @@ ex_endtry(exarg_T *eap)
 	     */
 	    if (did_throw)
 		discard_current_exception();
+
+	    // report eap->errmsg, also when there already was an error
+	    did_emsg = FALSE;
 	}
 	else
 	{
@@ -2105,7 +2109,9 @@ ex_endtry(exarg_T *eap)
 	 */
 	(void)cleanup_conditionals(cstack, CSF_TRY | CSF_SILENT, TRUE);
 
-	leave_block(cstack);
+	if (cstack->cs_idx >= 0
+			       && (cstack->cs_flags[cstack->cs_idx] & CSF_TRY))
+	    leave_block(cstack);
 	--cstack->cs_trylevel;
 
 	if (!skip)

src/testdir/test_trycatch.vim

@@ -2295,5 +2295,25 @@ func Test_error_in_catch_and_finally()
   call delete('XtestCatchAndFinally')
 endfunc
 
+" This was causing an illegal memory access
+func Test_leave_block_in_endtry_not_called()
+  let lines =<< trim END
+      vim9script
+      try #
+      for x in []
+      if
+      endwhile
+      if
+      endtry
+  END
+  call writefile(lines, 'XtestEndtry')
+  try
+    source XtestEndtry
+  catch /E171:/
+  endtry
+
+  call delete('XtestEndtry')
+endfunc
+
 " Modeline								    {{{1
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker

src/version.c

@@ -757,6 +757,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3486,
 /**/
     3485,
 /**/