[Python-Dev] Problem with the memory docs (original) (raw)

Tim Peters tim.one@comcast.net
Fri, 05 Apr 2002 05:12:56 -0500

I'm not following this at all. Calling malloc(1) does exactly what Guido wants. "malloc(1)" isn't a broken Unix manpage reference, if that's how you're reading it; it means call malloc with an argument of 1.

[Martin]

I think I'm now getting to the root of your confusion. Calling malloc(1) is not what Guido wants. Instead, he wants that pymalloc(0) returns a non-null pointer "normally".

And there's no better way to be 100% clear about what that means than to specify a trivial implementation that satisfies it. It doesn't need a pile of words like this:

Now, there are some C libraries which normally return a NULL pointer for malloc(0); as you point out, C gives them the freedom to do so. To work-around this under-specification, one can call malloc(1) - standards mandate that this does attempt to allocate something. It may be possible to find different work-arounds, but this is the most straight-forward one.

Writing an essay on malloc() isn't going to make the docs clearer than saying PyMem_Malloc(0) acts like malloc(1). Even the C standard is reduced to saying "the behavior is as if the size were some nonzero value" when a platform chooses not to return NULL every time malloc(0) is called. I'm saying straight out that Python's choice for "some nonzero value" is always

  1. It couldn't be clearer or briefer than that: both rigorously correct and intuitively clear with one shot.

If there's something you want to see done here, please say what it is, or suggest the exact words you want to see in the docs.