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

Wed Nov 16 13:11:26 CET 2005

By the way, I liked the sound of the arena/pool tree - really good idea.
Thomas Lee wrote:
>Niko Matsakis wrote:
>>>>>>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.
>>>>>>>>>>>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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