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

diff --git a/src/output/driver.c b/src/output/driver.c
index fb5444ec14cb2dc76fa64fbef7dfd97f31c75e76..da448b31707c8154c8ad2e3f99d0342c0115500d 100644 (file)
--- 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;
 }