[Python-Dev] Debug entry points for PyMalloc

[Michael Hudson]

Tim Peters <tim.one@comcast.net> writes:

> [Michael Hudson]
> > ...
> > Presuambly it would be possible to do this wrapped around malloc() &
> > free() too?
> 
> Provided they were spelled PyMem_Malloc etc, sure.  The debug routines as
> sketched don't make any secret assumptions about the underlying allocators
> they call.

That's what I thought.

> > No real point, I guess.
> 
> There may be an excellent point to it:  one of the pad bytes could be used
> to record which "API family" a block of memory came from.  Then a
> mismatching realloc/free could be caught directly at the time it happened.

Good point!

> >> + The Debug free first uses the address to find the number of bytes
> >>   originally asked for, then checks the 8 bytes on each end for
> >>   sanity (in particular, that the PYMALLOC_FORBIDDENBYTEs are still
> >>   intact).
> >>   XXX Make this checking a distinct entry point.
> 
> > Yes.  Particularly if you can call it from gdb.
> 
> Is something extraordinary required to make that possible?  I had in mind
> nothing fancier than
> 
> extern void _PyMalloc_DebugCheckAddress(void* p);

Dunno.  I ought to learn how to use gdb properly.

[...]
> > ...
> > What are you waiting for? <wink>
> 
> For endless silly objections to fade away <wink>.

Well, if you consider my comments to be objections, feel free to
consider them to be written in very faint writing :)

Cheers,
M.

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