[Cython] Temp allocation bug

[Robert Bradshaw]

On Jan 17, 2009, at 3:02 PM, Dag Sverre Seljebotn wrote:

> It  is supposed to work, that's why generate_disposal_code and  
> free_temps are seperate calls. The former can be called multiple  
> times in generate_..._code, the latter must be called exactly once.  
> The temporary variable will be held on to until the end of the C  
> branch, which is optimized away by gcc.
>
> You'll find examples somewhere of this, but I can't remember where  
> at the moment.

Sure. I'm was just musing about it not meshing well with old vs. new  
temps, which is the real issue that needs attention.

- Robert

> Dag Sverre Seljebotn
> -----Original Message-----
> From: Robert Bradshaw <robertwb at math.washington.edu>
> Date: Saturday, Jan 17, 2009 11:37 pm
> Subject: Re: [Cython] Temp allocation bug
> To: cython-dev at codespeak.netReply-To: cython-dev at codespeak.net
>
> On Jan 17, 2009, at 2:20 PM, Dag Sverre Seljebotn wrote:
>>
>>> Robert wrote:
>>> Is this going to be a general problem with any inside a
>>> NewTempExprNode (plain) ExprNode? That could be bad. On that  
>>> note, is
>>> there any reason that temp freeing is done as a separate step now
>>> instead of as part of the disposal code? (Someone more familiar with
>>> the new code probably has a trivial answer to this.)
>>
>>> Some code is generated like this:
>>
>>> /*allocate node*/
>> if (something) {
>>   block A
>>   /* deallocate node */
>> } else {
>>   block B
>>   /* deallocate node */
>> }
>>
>>> If temp releasing is tied up with disposal, the temp can be
>> reallocated
>> and reused in block B, leading to disaster. Also it would be released
>> twice. Etc.
>>
>>> If the C control flow matched the node tree, this wouldn't be a
>> problem,
>> but it doesn't.
>>
>>> Pyrex didn't have this problem, but that meant that deallocation  
>>> (i.e.
>> decrefs) is done later than necesarry.
>>
>> Ah, I see.
>>
>> Well, I'd rather deallocate too late than deallocate incorrectly.
>> Does this mean that it's all or nothing with the NewTempExprNodes, or
>> is a mix and match supposed to work?
>>
>> - Robert
>>
>> _______________________________________________
>> Cython-dev mailing list
>> Cython-dev at codespeak.net
>> http://codespeak.net/mailman/listinfo/cython-dev
>>
>
> _______________________________________________
> Cython-dev mailing list
> Cython-dev at codespeak.net
> http://codespeak.net/mailman/listinfo/cython-dev