[Python-Dev] tests failing in 2.2.2 (original) (raw)

Guido van Rossum guido@python.org
Tue, 08 Oct 2002 16:25:06 -0400

[Guido, on the list(xrange(maxint // 4)) test] > That's strange -- that test is specifically designed to fail before it > ever gets to allocating memory. Can you track this down with a > debugger?

[Martin] > Notice that this test does not strictly achieve that:

[Tim]

This is true, although I'd say it plain doesn't achieve that, and leave "strictly" out of it.

> with a four-byte pointer, you attempt to allocate 0x20000000L items (due > to roundupsize), which is small enough to try a realloc. In turn, it > tries to allocate 0x80000000L bytes, i.e. 2GB. On a 32-bit machine, it > is possible to allocate that much memory. Depending on platform, of course. Under MSVC6, it does call the platform realloc(), and it's the latter that returns a NULL pointer (the max you can alloc under Win32 is 0x7ffdefff). If we changed the test to use maxint // 2 instead, it would (just barely) trigger the newsize <= ((~(sizet)0) / sizeof(type)) test in NRESIZE instead, and keep the platform realloc() out of it. Good enough?

[Guido] I'd say so, except I fear that it might cause different problems (not that I know of any). I tried it on Linux and on Win98 and it works fine. I presume you've tested it on Win2K.

But wasn't it specifically designed to catch a condition that was only true when the size was (approximately) maxint/4?

--Guido van Rossum (home page: http://www.python.org/~guido/)