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Memory leaks in Tidy 2 Jul 99

From: Terry Teague <teague@macbroker.com>
Date: Sat, 3 Jul 1999 14:03:56 -0700
Message-Id: <l03130306b3a424766157@[17.219.105.242]>
To: html-tidy@w3.org
Dear Folks,

I have recently joined this mailing list - although I have been reading all
the archives, there are number of things I wanted to say, which means
signing up for the mailing list. I was hoping to reduce the amount of mail
I was getting <grin>.

Anyway, I am the person responsible for porting "tidy" to Mac OS. I have
ported all versions of Dave's excellent code to the Mac OS, since the
version released 01 Sep 98, both as command-line driven applications
(minimal porting required), and with a GUI front-end.

If you are interested, you can get more info on the ports from my web page :

<http://www.geocities.com/SiliconValley/1057/tidy.html>

I have learnt a lot during this porting process, and as I see questions
occasionally related to other ports or bugs discovered being posted, I
think I can provide some input. Originally I was going send this input to
Dave in private EMail, but I have decided it will benefit others (perhaps
at the risk of embarrasing Dave <grin>) if I share the info with the list.

OK, here goes the first issue :

Memory leaks in Tidy.

In a command-line environment or other standalone application cases, memory
leaks are usually not a problem, as memory is cleaned up on quit. But for
other environments, memory leaks are a problem.

In the process of tracking down some memory management related issues in my
ports, I threw various debugging tools I had in my possesion, as well as
some home-grown debugging code, at the problems. A number of memory leaks
were discovered, primarily starting with the 15 Apr 99 version (since that
was pretty much a rewrite of a lot of code). Independently, Jeffrey Wang
found basically the same memory leaks, as per his EMail :

<http://lists.w3.org/Archives/Public/html-tidy/1999AprJun/0032.html>

>(1)
>inside void FreeEntities(void) in entities.c
>
>should call
>        MemFree(next->name)
>before calling
>        MemFree(next)
>otherwise there is memory leak
>
>(2)
>inside void FreeTags(void) in tags.c
>
>should call
>        MemFree(next->name)
>before calling
>        MemFree(next)
>otherwise there is memory leak
>
>(4)
>inside pprint.c
>
>memory leak caused by buffer allocated for linebuf.

These same leaks are still in current versions. And an additional memory
leak that appeared in recent versions in "config.c".

I haven't decided how I will fix the memory leak that is in "pprint.c" for
the linebuf, but here is the fix I made for the leak in "config.c" :

In FreeConfig() before the calls to MemFree(), add the following :

   /* TRT */
    PList *prev, *next;
    int i;

    for (i = 0; i < HASHSIZE; ++i)
    {
        prev = null;
        next = hashtable[i];

        while(next)
        {
            prev = next->next;
            MemFree(next->name);
            MemFree(next);
            next = prev;
        }
    }

Somewhat related in FreeConfig() - if you don't use a Config file, 2 NULL
objects (slide_style and doctype_str ) are freed - passing NULL to free()
is safe according to K&R; if you use a different memory allocator, as I
sometimes do in my ports, you may need to check for NULL pointers (my debug
version of memory management routines trapped these 2 NULL pointers).

If you would like more info on the memory leaks, let me know.

Regards, Terry Teague
Received on Saturday, 3 July 1999 17:04:51 GMT

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