patch 8.1.1579: dict and list could be GC'ed while displaying error

Problem:    Dict and list could be GC'ed while displaying error in a timer.
            (Yasuhiro Matsumoto)
Solution:   Block garbage collection when executing a timer.  Add
            test_garbagecollect_soon(). Add "no_wait_return" to
            test_override(). (closes #4571)

runtime/doc/eval.txt

@@ -2741,6 +2741,7 @@ test_alloc_fail({id}, {countdown}, {repeat})
 test_autochdir()		none	enable 'autochdir' during startup
 test_feedinput({string})	none	add key sequence to input buffer
 test_garbagecollect_now()	none	free memory right now for testing
+test_garbagecollect_soon()	none	free memory soon for testing
 test_getvalue({string})		any	get value of an internal variable
 test_ignore_error({expr})	none	ignore a specific error
 test_null_blob()		Blob	null value for testing
@@ -10009,6 +10010,10 @@ test_garbagecollect_now()			 *test_garbagecollect_now()*
 		internally, and |v:testing| must have been set before calling
 		any function.
 
+test_garbagecollect_soon()			 *test_garbagecollect_soon()*
+		Set the flag to call the garbagecollector as if in the main
+		loop.  Only to be used in tests.
+
 test_getvalue({name})					*test_getvalue()*
 		Get the value of an internal variable.  These values for
 		{name} are supported:
@@ -10072,6 +10077,8 @@ test_override({name}, {val})				*test_override()*
 			     fallback to the old engine
 		no_query_mouse  do not query the mouse position for "dec"
 				terminals
+		no_wait_return	set the "no_wait_return" flag.  Not restored
+				with "ALL".
 		ALL	     clear all overrides ({val} is not used)
 
 		"starting" is to be used when a test should behave like

src/dict.c

@@ -28,7 +28,7 @@ dict_alloc(void)
 {
     dict_T *d;
 
-    d = ALLOC_ONE(dict_T);
+    d = ALLOC_CLEAR_ONE(dict_T);
     if (d != NULL)
     {
 	/* Add the dict to the list of dicts for garbage collection. */
@@ -811,7 +811,7 @@ dict_get_tv(char_u **arg, typval_T *rettv, int evaluate)
     {
 	semsg(_("E723: Missing end of Dictionary '}': %s"), *arg);
 failret:
-	if (evaluate)
+	if (d != NULL)
 	    dict_free(d);
 	return FAIL;
     }

src/evalfunc.c

@@ -448,6 +448,7 @@ static void f_test_option_not_set(typval_T *argvars, typval_T *rettv);
 static void f_test_override(typval_T *argvars, typval_T *rettv);
 static void f_test_refcount(typval_T *argvars, typval_T *rettv);
 static void f_test_garbagecollect_now(typval_T *argvars, typval_T *rettv);
+static void f_test_garbagecollect_soon(typval_T *argvars, typval_T *rettv);
 static void f_test_ignore_error(typval_T *argvars, typval_T *rettv);
 static void f_test_null_blob(typval_T *argvars, typval_T *rettv);
 #ifdef FEAT_JOB_CHANNEL
@@ -1019,6 +1020,7 @@ static struct fst
     {"test_autochdir",	0, 0, f_test_autochdir},
     {"test_feedinput",	1, 1, f_test_feedinput},
     {"test_garbagecollect_now",	0, 0, f_test_garbagecollect_now},
+    {"test_garbagecollect_soon",	0, 0, f_test_garbagecollect_soon},
     {"test_getvalue",	1, 1, f_test_getvalue},
     {"test_ignore_error",	1, 1, f_test_ignore_error},
     {"test_null_blob",	0, 0, f_test_null_blob},
@@ -14460,6 +14462,8 @@ f_test_override(typval_T *argvars, typval_T *rettv UNUSED)
 	    nfa_fail_for_testing = val;
 	else if (STRCMP(name, (char_u *)"no_query_mouse") == 0)
 	    no_query_mouse_for_testing = val;
+	else if (STRCMP(name, (char_u *)"no_wait_return") == 0)
+	    no_wait_return = val;
 	else if (STRCMP(name, (char_u *)"ALL") == 0)
 	{
 	    disable_char_avail_for_testing = FALSE;
@@ -14550,6 +14554,15 @@ f_test_garbagecollect_now(typval_T *argvars UNUSED, typval_T *rettv UNUSED)
     garbage_collect(TRUE);
 }
 
+/*
+ * "test_garbagecollect_soon()" function
+ */
+    static void
+f_test_garbagecollect_soon(typval_T *argvars UNUSED, typval_T *rettv UNUSED)
+{
+    may_garbage_collect = TRUE;
+}
+
 /*
  * "test_ignore_error()" function
  */

src/testdir/test_timers.vim

@@ -309,4 +309,28 @@ func Test_restore_count()
   call delete('Xtrctext')
 endfunc
 
+" Test that the garbage collector isn't triggered if a timer callback invokes
+" vgetc().
+func Test_nocatch_garbage_collect()
+  " 'uptimetime. must be bigger than the timer timeout
+  set ut=200
+  call test_garbagecollect_soon()
+  call test_override('no_wait_return', 0)
+  func CauseAnError(id)
+    " This will show an error and wait for Enter.
+    let a = {'foo', 'bar'}
+  endfunc
+  func FeedChar(id)
+    call feedkeys('x', 't')
+  endfunc
+  call timer_start(300, 'FeedChar')
+  call timer_start(100, 'CauseAnError')
+  let x = getchar()
+
+  set ut&
+  call test_override('no_wait_return', 1)
+  delfunc CauseAnError
+  delfunc FeedChar
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -777,6 +777,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1579,
 /**/
     1578,
 /**/