[Python-Dev] Memory management in the AST parser & compiler

[Thomas Lee]

By the way, I liked the sound of the arena/pool tree - really good idea.

Thomas Lee wrote:

>Niko Matsakis wrote:
>
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>>>Boy am I wanting RAII from C++ for automatic freeing when scope is
>>>left.  Maybe we need to come up with a similar thing, like all memory
>>>that should be freed once a scope is left must use some special struct
>>>that stores references to all created memory locally and then a free
>>>call must be made at all exit points in the function using the special
>>>struct.  Otherwise the pointer is stored in the arena and handled
>>>en-mass later.
>>>   
>>>
>>>      
>>>
>>That made sense.  I think I'd be opposed to what you describe here  
>>just because I think anything which *requires* that cleanup code be  
>>placed on every function is error prone.
>>
>> 
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>Placing it in every function isn't really the problem: at the moment 
>it's more the fact we have to keep track of too many variables at any 
>given time to properly deallocate it all. Cleanup code gets tricky very 
>fast.
>
>Then it gets further complicated by the fact that 
>stmt_ty/expr_ty/mod_ty/etc. deallocate members (usually asdl_seq 
>instances in my experience) - so if a construction takes place, all of a 
>sudden you have to make sure you don't deallocate those members a second 
>time in the cleanup code :S it gets tricky very quickly.
>
>Even if it meant we had just one function call - one, safe function call 
>that deallocated all the memory allocated within a function - that we 
>had to put before each and every return, that's better than what we 
>have. Is it the best solution? Maybe not. But that's what we're looking 
>for here I guess :)
>
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