Re: [Scidvspc-users] [PATCH] fix memory leak in pgn parser (wrt. character detector)

[Steve A <ste...@gm...>]

Many thanks for that Ali. :)

Steven

On Tue, Oct 4, 2016 at 6:18 AM, Ali Polatel <al...@ex...> wrote:

> Hello everyone,
>
> I have spotted a memory leak in the pgn parser. This makes Scid pretty much
> unusuable for me after working on the tree window for a while.
>
> Below is the valgrind output of the incident:
>
> 138,880 bytes in 248 blocks are definitely lost in loss record 774 of 818
>    at 0x4C2A0FC: operator new(unsigned long) (in
> /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
>    by 0x44E57D: PgnParser::Reset(char const*) (in /usr/bin/tkscid)
>    by 0x45358E: StoredLine::Init() (in /usr/bin/tkscid)
>    by 0x453748: StoredLine::StoredLine(Position*) (in /usr/bin/tkscid)
>    by 0x42D23C: sc_tree_search(void*, Tcl_Interp*, int, char const**) (in
> /usr/bin/tkscid)
>    by 0x42EBEF: sc_tree(void*, Tcl_Interp*, int, char const**) (in
> /usr/bin/tkscid)
>    by 0x50889B5: TclInvokeStringCommand (in /usr/lib/libtcl8.6.so)
>    by 0x508D5F6: TclNRRunCallbacks (in /usr/lib/libtcl8.6.so)
>    by 0x508F701: TclEvalEx (in /usr/lib/libtcl8.6.so)
>    by 0x508FCB2: Tcl_EvalEx (in /usr/lib/libtcl8.6.so)
>    by 0x543DFAD: Tk_BindEvent (in /usr/lib/libtk8.6.so)
>    by 0x5441F5C: TkBindEventProc (in /usr/lib/libtk8.6.so)
>
> The problem is PgnParser::Reset() is be called from multiple
> different functions and during some cases CharConverter is
> already allocated. Overwriting the variable to NULL causes
> the previously allocated memory to leak.
>
> To reproduce open a giant scid database in the tree and browse the games
> for a while. In about half an hour scid running on a 4G RAM box eats all
> the memory and hits OOM.
>
> The change moves the initialisation of CharConverter and CharDetector to
> PgnParser::Init(). We do not need to set them to NULL in PgnParser::Reset()
> due to the fact that all callers also call CreateCharsetDetector() which
> takes
> care of the initialisation.
>
> I have been running Scid with this patch all day today and it seems to
> cause no regressions and the memory usage is OK.
>
> Signed-off-by: Ali Polatel <al...@ex...>
> ---
>  src/pgnparse.cpp | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/src/pgnparse.cpp b/src/pgnparse.cpp
> index bdfc4f9..a49e894 100644
> --- a/src/pgnparse.cpp
> +++ b/src/pgnparse.cpp
> @@ -37,6 +37,8 @@ void
>  PgnParser::Init ()
>  {
>      ErrorBuffer = new DString;
> +    CharConverter = NULL;
> +    CharDetector = NULL;
>      Reset();
>  }
>
> @@ -56,8 +58,6 @@ PgnParser::Reset()
>      ResultWarnings = true;
>      NewlinesToSpaces = true;
>      NumIgnoredTags = 0;
> -    CharConverter = NULL;
> -    CharDetector = NULL;
>  }
>
>  void
> --
> 2.10.0
>
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