From 31127c303d92ce811f1dd365af83644266e4fd88 Mon Sep 17 00:00:00 2001
From: John Darrington <john@darrington.wattle.id.au>
Date: Sun, 28 Apr 2019 15:09:02 +0200
Subject: [PATCH] src/output/driver.c:  Change engine_stack from an array to a
 list.

The structure called engine_stack was formerly implemented as a heap
based array allocated with realloc.   However when realloc moves data
it makes only shallow copies and does not copy referand of pointers.
This was causing crashes under certain circumstances.

Rather than trying to fix this, this change re-implements engine_stack
using the linked list structure from ll.h
---
 src/output/driver.c | 48 ++++++++++++++++++++-------------------------
 1 file changed, 21 insertions(+), 27 deletions(-)

diff --git a/src/output/driver.c b/src/output/driver.c
index fb5444ec14..da448b3170 100644
--- a/src/output/driver.c
+++ b/src/output/driver.c
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
-   Copyright (C) 1997-9, 2000, 2007, 2009, 2010, 2011, 2012, 2014 Free Software Foundation, Inc.
+   Copyright (C) 1997-9, 2000, 2007, 2009, 2010, 2011, 2012, 2014, 2019 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -51,6 +51,7 @@
 
 struct output_engine
   {
+    struct ll ll;                  /* Node for this engine. */
     struct llx_list drivers;       /* Contains "struct output_driver"s. */
     struct string deferred_syntax; /* TEXT_ITEM_SYNTAX being accumulated. */
     char *command_name;            /* Name of command being processed. */
@@ -67,17 +68,15 @@ struct output_engine
     struct string_map heading_vars;
   };
 
-static const struct output_driver_factory *factories[];
+static struct ll_list engine_stack = LL_INITIALIZER (engine_stack);
 
-/* A stack of output engines.. */
-static struct output_engine *engine_stack;
-static size_t n_stack, allocated_stack;
+static const struct output_driver_factory *factories[];
 
 static struct output_engine *
 engine_stack_top (void)
 {
-  assert (n_stack > 0);
-  return &engine_stack[n_stack - 1];
+  struct ll *head = ll_head (&engine_stack);
+  return ll_data (head, struct output_engine, ll);
 }
 
 static void
@@ -95,14 +94,8 @@ put_strftime (const char *key, const char *format,
 void
 output_engine_push (void)
 {
-  struct output_engine *e;
+  struct output_engine *e = xzalloc (sizeof (*e));
 
-  if (n_stack >= allocated_stack)
-    engine_stack = x2nrealloc (engine_stack, &allocated_stack,
-                               sizeof *engine_stack);
-
-  e = &engine_stack[n_stack++];
-  memset (e, 0, sizeof *e);
   llx_init (&e->drivers);
   ds_init_empty (&e->deferred_syntax);
 
@@ -112,15 +105,16 @@ output_engine_push (void)
   const struct tm *tm = localtime (&t);
   put_strftime ("Date", "%x", tm, &e->heading_vars);
   put_strftime ("Time", "%X", tm, &e->heading_vars);
+
+  ll_push_head (&engine_stack, &e->ll);
 }
 
 void
 output_engine_pop (void)
 {
-  struct output_engine *e;
+  struct ll *head = ll_pop_head (&engine_stack);
+  struct output_engine *e =ll_data (head, struct output_engine, ll);
 
-  assert (n_stack > 0);
-  e = &engine_stack[--n_stack];
   while (!llx_is_empty (&e->drivers))
     {
       struct output_driver *d = llx_pop_head (&e->drivers, &llx_malloc_mgr);
@@ -134,6 +128,7 @@ output_engine_pop (void)
     free (e->groups[i]);
   free (e->groups);
   string_map_destroy (&e->heading_vars);
+  free (e);
 }
 
 void
@@ -266,13 +261,10 @@ output_submit (struct output_item *item)
 const char *
 output_get_command_name (void)
 {
-  if (n_stack)
-    {
-      struct output_engine *e = engine_stack_top ();
-      for (size_t i = e->n_groups; i-- > 0; )
-        if (e->groups[i])
-          return e->groups[i];
-    }
+  struct output_engine *e = engine_stack_top ();
+  for (size_t i = e->n_groups; i-- > 0; )
+    if (e->groups[i])
+      return e->groups[i];
 
   return NULL;
 }
@@ -377,9 +369,11 @@ output_driver_get_engine (const struct output_driver *driver)
 {
   struct output_engine *e;
 
-  for (e = engine_stack; e < &engine_stack[n_stack]; e++)
-    if (llx_find (llx_head (&e->drivers), llx_null (&e->drivers), driver))
-      return e;
+  ll_for_each (e, struct output_engine, ll, &engine_stack)
+    {
+      if (llx_find (llx_head (&e->drivers), llx_null (&e->drivers), driver))
+	return e;
+    }
 
   return NULL;
 }
-- 
2.30.2