Some customizable memory allocators I know have an extra parameter "void *opaque" that is passed to all functions:">

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Le mercredi 19 juin 2013, Scott Dial a écrit :

On 6/18/2013 4:40 PM, Victor Stinner wrote:

> No context argument



I think there is a lack of justification for the extra argument, and the

extra argument is not free. The typical use-case for doing this

continuation-passing style is when the set of contexts is either

unknown, arbitrarily large, or infinite. In other words, when it would

be either impossible or impractical to enumerate all of the contexts.

However, in this case, we have only 3.

See the use case 3 in examples. Without the context argument, you have to copy/paste 3 times each functions: 3 functions -> 9 functions. I don't like having to copy/paste code, it sounds like a bad design.

And in the latter case, there is no extra indirect branching in the
hot-path of the allocators.
Are you concerned by performances? Did you see the Performances section, there is no overhead according to the benchmark suite.

Also, none of the external libraries cited introduce this CPS/ctx stuff.

Oops, the list is incomplete. Copy/paste from the issue:

Some customizable memory allocators I know have an extra parameter "void \*opaque" that is passed to all functions:


- in zlib: zalloc and zfree: http://www.zlib.net/manual.html#Usage
- same thing for bz2.
- lzma's ISzAlloc: http://www.asawicki.info/news_1368_lzma_sdk_-_how_to_use.html
- Oracle's OCI: http://docs.oracle.com/cd/B10501_01/appdev.920/a96584/oci15re4.htm


OTOH, expat, libxml, libmpdec don't have this extra parameter.
Victor