[Image-SIG] AccessInit: hash collision: 3 for both 1 and 1

[Fredrik Lundh]

The error should only occur if the C module's initialization function
is called twice.  That shouldn't happen under normal use of Python
(and if it happens anyway, it invariably results in resource leaks for
many modules, and potentially also more serious issues -- the C module
interface doesn't have a "uninit" mechanism).  Changing the init to
ignore double initializations only addresses the symptoms.

(the reason this is a hard error is that collision under normal
circumstances means that the library is unusable unless rebuilt with
proper hash settings).

Googling led me to someone mentioning that this happened after he'd
used easy_install, but that it went away after rebuilding with
setup.py.  How did you build your copy?

</F>

On Thu, Apr 8, 2010 at 8:17 PM, Bill Janssen <janssen at parc.com> wrote:
> Fredrik Lundh <fredrik at pythonware.com> wrote:
>
>> The idea is that add_item should only be called once for each mode
>> (see ImagingAccessInit).  What did you do to trick Python into calling
>> the module initializer multiple times?
>
> I was using epydoc and docutils 0.5 to build my documentation.  Epydoc
> crashed with this error.  If you google "AccessInit: hash collision: 3
> for both 1 and 1", you'll see it's not just me.  After I applied my
> patch, things seem to work fine.
>
> Seems to be a problem with Django and Sphinx and Satchmo, too.  And
> it looks like maybe it only occurs on Windows.  I ran into it using
> PIL built with msys for Python 2.6.4 on Windows XP.  I've never seen
> it on OS X or Ubuntu or Fedora.
>
> By the way, "exit(1)" is pretty harsh.  Shouldn't you somehow throw a
> Python exception there?  Give us a better chance of figuring out where
> it's being called from.
>
> Bill
>
>>
>> </F>
>>
>> On Mon, Apr 5, 2010 at 4:41 AM, Bill Janssen <janssen at parc.com> wrote:
>> > Seems to me that in libImaging, Access.c:add_item should really read
>> >
>> > static ImagingAccess
>> > add_item(const char* mode)
>> > {
>> >    UINT32 i = hash(mode);
>> >    /* printf("hash %s => %d\n", mode, i); */
>> >    if (access_table[i].mode && (strcmp(mode, access_table[i].mode) != 0)) {
>> >        fprintf(stderr, "AccessInit: hash collision: %d for both %s and %s\n",
>> >                i, mode, access_table[i].mode);
>> >        exit(1);
>> >    }
>> >    access_table[i].mode = mode;
>> >    return &access_table[i];
>> > }
>> >
>> > Currently, it reads:
>> >
>> > static ImagingAccess
>> > add_item(const char* mode)
>> > {
>> >    UINT32 i = hash(mode);
>> >    /* printf("hash %s => %d\n", mode, i); */
>> >    if (access_table[i].mode) {
>> >        fprintf(stderr, "AccessInit: hash collision: %d for both %s and %s\n",
>> >                i, mode, access_table[i].mode);
>> >        exit(1);
>> >    }
>> >    access_table[i].mode = mode;
>> >    return &access_table[i];
>> > }
>> >
>> > And there's a number of Google hits for "AccessInit: hash collision: 3
>> > for both 1 and 1", starting about the release of 1.1.7.
>> >
>> > Bill
>> > _______________________________________________
>> > Image-SIG maillist  -  Image-SIG at python.org
>> > http://mail.python.org/mailman/listinfo/image-sig
>> >
>