[RFA 14/14] Changes to solib-svr4.c

[Gary Benson]

This patch modifies svr4_free_so to free the containing so_list
object, and adds the acquire/release logic described in [1].
Note that there is a more programmatic description of this in
the final hunk of this patch.

[1] http://sourceware.org/ml/gdb-patches/2013-07/msg00298.html
-------------- next part --------------
2013-07-10  Gary Benson  <gbenson@redhat.com>

	* solib-svr4.c (struct lm_info): New fields "copy" and "acquired".
	(svr4_free_so): Add acquired copy logic.  Free the containing
	so_list when freeing is required.
	(svr4_copy_library_list): Remove.
	(svr4_current_sos): Replace call to svr4_copy_library_list with
	acquired copy logic.

diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
index 6f8d0ef..cab46f1 100644
--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -72,6 +72,15 @@ struct lm_info
 
     /* Values read in from inferior's fields of the same name.  */
     CORE_ADDR l_ld, l_next, l_prev, l_name;
+
+    /* A copy of the solib containing this lm_info, if one exists.
+       See comment in svr4_current_sos for more information.  */
+    struct so_list *copy;
+
+    /* Nonzero if the solib containing this lm_info is an acquired
+       copy of another solib.  See comment in svr4_current_sos for
+       more information.  */
+    unsigned int acquired : 1;
   };
 
 /* On SVR4 systems, a list of symbols in the dynamic linker where
@@ -1055,7 +1064,29 @@ struct svr4_library_list
 static void
 svr4_free_so (struct so_list *so)
 {
+  if (so->lm_info)
+    {
+      /* If this library is an acquired copy then release it. */
+      if (so->lm_info->acquired)
+	{
+	  so->lm_info->acquired = 0;
+	  return;
+	}
+
+      /* If the library has an acquired copy then unhook it.  */
+      if (so->lm_info->copy && so->lm_info->copy->lm_info->acquired)
+	{
+	  so->lm_info->copy->lm_info->acquired = 0;
+	  so->lm_info->copy = NULL;
+	}
+
+      /* If the library has an unacquired copy then free it.  */
+      if (so->lm_info->copy)
+	svr4_free_so (so->lm_info->copy);
+    }
+
   xfree (so->lm_info);
+  xfree (so);
 }
 
 /* Implement target_so_ops.clear_so.  */
@@ -1083,34 +1114,6 @@ svr4_free_library_list (void *p_list)
     }
 }
 
-/* Copy library list.  */
-
-static struct so_list *
-svr4_copy_library_list (struct so_list *src)
-{
-  struct so_list *dst = NULL;
-  struct so_list **link = &dst;
-
-  while (src != NULL)
-    {
-      struct so_list *new;
-
-      new = xmalloc (sizeof (struct so_list));
-      memcpy (new, src, sizeof (struct so_list));
-
-      new->lm_info = xmalloc (sizeof (struct lm_info));
-      memcpy (new->lm_info, src->lm_info, sizeof (struct lm_info));
-
-      new->next = NULL;
-      *link = new;
-      link = &new->next;
-
-      src = src->next;
-    }
-
-  return dst;
-}
-
 #ifdef HAVE_LIBEXPAT
 
 #include "xml-support.h"
@@ -1470,7 +1473,62 @@ svr4_current_sos (void)
   /* If the solib list has been read and stored by the probes
      interface then we return a copy of the stored list.  */
   if (info->solib_list != NULL)
-    return svr4_copy_library_list (info->solib_list);
+    {
+      struct so_list *so, *result, **link = &result;
+
+      /* To avoid copying each solib each time the list is updated,
+	 we retain pointers to the copies and mark each copy as
+	 "acquired" before returning the list to update_solib_list.
+	 Then, for each copy:
+
+         - If the solib has already been added to the program space's
+           so_list then update_solib_list will free the copy we
+           returned using free_so.  This releases the acquired copy
+           for re-use by the next call to svr4_current_sos.
+
+         - If the solib has not been added to the program space's
+           so_list then update_solib_list will not free the copy we
+           returned.  The next call to svr4_current_sos will note that
+           the copy is still acquired and create a fresh copy to
+           return.
+
+         This ensures no solib is copied more than twice. */
+      for (so = info->solib_list; so; so = so->next)
+	{
+	  gdb_assert (so->lm_info != NULL);
+
+	  /* If the library has an acquired copy then unhook it.  */
+	  if (so->lm_info->copy && so->lm_info->copy->lm_info->acquired)
+	    {
+	      so->lm_info->copy->lm_info->acquired = 0;
+	      so->lm_info->copy = NULL;
+	    }
+
+	  /* If this library does not have a copy then create one.  */
+	  if (so->lm_info->copy == NULL)
+	    {
+	      struct so_list *copy;
+
+	      copy = XZALLOC (struct so_list);
+	      memcpy (copy, so, sizeof (struct so_list));
+
+	      copy->lm_info = xmalloc (sizeof (struct lm_info));
+	      memcpy (copy->lm_info, so->lm_info, sizeof (struct lm_info));
+
+	      so->lm_info->copy = copy;
+	    }
+
+	  /* Mark the copy as acquired and link it into the result.  */
+	  gdb_assert (!so->lm_info->copy->lm_info->acquired);
+	  so->lm_info->copy->lm_info->acquired = 1;
+
+	  so->lm_info->copy->next = NULL;
+	  *link = so->lm_info->copy;
+	  link = &so->lm_info->copy->next;
+	}
+
+      return result;
+    }
 
   /* Otherwise obtain the solib list directly from the inferior.  */
   return svr4_current_sos_direct (info);