Patchwork [RFA] Fix splay tree KEY leak detected in GDB test gdb.base/macscp.exp

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Submitter Philippe Waroquiers
Date Jan. 26, 2019, 10:34 p.m.
Message ID <20190126223435.9411-1-philippe.waroquiers@skynet.be>
Download mbox | patch
Permalink /patch/31221/
State New
Headers show

Comments

Philippe Waroquiers - Jan. 26, 2019, 10:34 p.m.
When a node is removed from a splay tree, the splay tree was
not using the function splay_tree_delete_key_fn to release the key.
This was causing a leak, fixed by Tom Tromey.

This patch fixes another key leak, that happens when a key equal to
a key already present is inserted.  In such a case, we have to release
the old KEY.
Note that this is based on the assumption that the caller always
allocates a new KEY when doing an insert.

Also, clarify the documentation about when the release functions are
called.

include/ChangeLog
2019-01-26  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* splay-tree.h (splay_tree_delete_key_fn): Update comment.
	(splay_tree_delete_value_fn): Likewise.

libiberty/ChangeLog
2019-01-26  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* splay-tree.c (splay_tree_insert): Also release old KEY in case
	of insertion of a key equal to an already present key.
	(splay_tree_new_typed_alloc): Update comment.
---
 include/splay-tree.h   | 11 +++++++++--
 libiberty/splay-tree.c | 13 ++++++++++---
 2 files changed, 19 insertions(+), 5 deletions(-)
Kevin Buettner - Feb. 3, 2019, 5:45 p.m.
On Sat, 26 Jan 2019 23:34:35 +0100
Philippe Waroquiers <philippe.waroquiers@skynet.be> wrote:

> include/ChangeLog
> 2019-01-26  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
> 
> 	* splay-tree.h (splay_tree_delete_key_fn): Update comment.
> 	(splay_tree_delete_value_fn): Likewise.
> 
> libiberty/ChangeLog
> 2019-01-26  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
> 
> 	* splay-tree.c (splay_tree_insert): Also release old KEY in case
> 	of insertion of a key equal to an already present key.
> 	(splay_tree_new_typed_alloc): Update comment.

These changes look reasonable to me, BUT...

I think you'll need to get approval for this patch from the gcc
maintainers.  The libiberty README file indicates that fixes should be
sent to gcc-patches@gcc.gnu.org.

Kevin
Philippe Waroquiers - Feb. 3, 2019, 5:58 p.m.
Thanks for looking at this.

The below change was discussed with Tom on irc.
Tom pushed a first fix in the splay tree, so it would be easier
for me if he (or someone else) could also push this one.

Thanks

Philippe


On Sun, 2019-02-03 at 10:45 -0700, Kevin Buettner wrote:
> On Sat, 26 Jan 2019 23:34:35 +0100
> Philippe Waroquiers <philippe.waroquiers@skynet.be> wrote:
> 
> > include/ChangeLog
> > 2019-01-26  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
> > 
> > 	* splay-tree.h (splay_tree_delete_key_fn): Update comment.
> > 	(splay_tree_delete_value_fn): Likewise.
> > 
> > libiberty/ChangeLog
> > 2019-01-26  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
> > 
> > 	* splay-tree.c (splay_tree_insert): Also release old KEY in case
> > 	of insertion of a key equal to an already present key.
> > 	(splay_tree_new_typed_alloc): Update comment.
> 
> These changes look reasonable to me, BUT...
> 
> I think you'll need to get approval for this patch from the gcc
> maintainers.  The libiberty README file indicates that fixes should be
> sent to gcc-patches@gcc.gnu.org.
> 
> Kevin
Tom Tromey - Feb. 5, 2019, 1:47 p.m.
>>>>> "Philippe" == Philippe Waroquiers <philippe.waroquiers@skynet.be> writes:

Philippe> The below change was discussed with Tom on irc.
Philippe> Tom pushed a first fix in the splay tree, so it would be easier
Philippe> for me if he (or someone else) could also push this one.

Did you send them to gcc-patches?
If so and they were approved, let me know and I will commit them
(though maybe not until Monday, depending).
If not, let me know, and I can forward the note, etc.

thanks,
Tom
Philippe Waroquiers - Feb. 5, 2019, 7:55 p.m.
On Tue, 2019-02-05 at 06:47 -0700, Tom Tromey wrote:
> > > > > > "Philippe" == Philippe Waroquiers <philippe.waroquiers@skynet.be> writes:
> 
> Philippe> The below change was discussed with Tom on irc.
> Philippe> Tom pushed a first fix in the splay tree, so it would be easier
> Philippe> for me if he (or someone else) could also push this one.
> 
> Did you send them to gcc-patches?
> If so and they were approved, let me know and I will commit them
> (though maybe not until Monday, depending).
> If not, let me know, and I can forward the note, etc.
No, I did not send it.
It would be really nice if you could take that in charge.

Also, there is a leak related to macro definition
(but not in splay tree), for which there is a patch series:
[RFAv3 0/2] Fix leaks in macro definition
https://sourceware.org/ml/gdb-patches/2019-01/msg00567.html

This series is still to be reviewed.

Thanks
Philippe
Tom Tromey - Feb. 6, 2019, 2:06 p.m.
>>>>> "Philippe" == Philippe Waroquiers <philippe.waroquiers@skynet.be> writes:

Philippe> No, I did not send it.
Philippe> It would be really nice if you could take that in charge.

I forwarded it:

https://gcc.gnu.org/ml/gcc-patches/2019-02/msg00323.html

Tom
Tom Tromey - Feb. 12, 2019, 1:13 p.m.
>>>>> "Philippe" == Philippe Waroquiers <philippe.waroquiers@skynet.be> writes:

>> Did you send them to gcc-patches?
>> If so and they were approved, let me know and I will commit them
>> (though maybe not until Monday, depending).
>> If not, let me know, and I can forward the note, etc.

Philippe> No, I did not send it.
Philippe> It would be really nice if you could take that in charge.

I've checked this in to gcc and binutils-gdb now.
Thanks for writing this.

Tom

Patch

diff --git a/include/splay-tree.h b/include/splay-tree.h
index 0d26272943..da533dec18 100644
--- a/include/splay-tree.h
+++ b/include/splay-tree.h
@@ -58,11 +58,18 @@  typedef struct splay_tree_node_s *splay_tree_node;
 typedef int (*splay_tree_compare_fn) (splay_tree_key, splay_tree_key);
 
 /* The type of a function used to deallocate any resources associated
-   with the key.  */
+   with the key.  If you provide this function, the splay tree
+   will take the ownership of the memory of the splay_tree_key arg
+   of splay_tree_insert.  This function is called to release the keys
+   present in the tree when calling splay_tree_delete or splay_tree_remove.
+   If splay_tree_insert is called with a key equal to a key already
+   present in the tree, the old key and old value will be released.  */
 typedef void (*splay_tree_delete_key_fn) (splay_tree_key);
 
 /* The type of a function used to deallocate any resources associated
-   with the value.  */
+   with the value.  If you provide this function, the memory of the
+   splay_tree_value arg of splay_tree_insert is managed similarly to
+   the splay_tree_key memory: see splay_tree_delete_key_fn.  */
 typedef void (*splay_tree_delete_value_fn) (splay_tree_value);
 
 /* The type of a function used to iterate over the tree.  */
diff --git a/libiberty/splay-tree.c b/libiberty/splay-tree.c
index 21d23c38df..4bbb39a62c 100644
--- a/libiberty/splay-tree.c
+++ b/libiberty/splay-tree.c
@@ -318,7 +318,11 @@  different types need to be allocated with different allocators.
 
 The splay tree will use @var{compare_fn} to compare nodes,
 @var{delete_key_fn} to deallocate keys, and @var{delete_value_fn} to
-deallocate values.
+deallocate values.  Keys and values will be deallocated when the
+tree is deleted using splay_tree_delete or when a node is removed
+using splay_tree_remove.  splay_tree_insert will release the previously
+inserted key and value using @var{delete_key_fn} and @var{delete_value_fn}
+if the inserted key is already found in the tree.
 
 @end deftypefn
 
@@ -372,10 +376,13 @@  splay_tree_insert (splay_tree sp, splay_tree_key key, splay_tree_value value)
 
   if (sp->root && comparison == 0)
     {
-      /* If the root of the tree already has the indicated KEY, just
-	 replace the value with VALUE.  */
+      /* If the root of the tree already has the indicated KEY, delete
+         the old key and old value, and replace them with KEY and  VALUE.  */
+      if (sp->delete_key)
+	(*sp->delete_key) (sp->root->key);
       if (sp->delete_value)
 	(*sp->delete_value)(sp->root->value);
+      sp->root->key = key;
       sp->root->value = value;
     } 
   else