argsort segfault

[mike fc]

Under benchmarking conditions, I can get argsort to segfault.

• Recent pypy nightly and numpy
• OSX Yosemite

pypy(46789,0x7fff7825b300) malloc: *** error for object 0x106702208: incorrect checksum for freed object - object was probably modified after being freed.
*** set a breakpoint in malloc_error_break to debug
Abort trap: 6

import timeit
import numpy as np

setup = "import numpy as np; a = np.random.rand(%i)"
stmt = "a.argsort()"

# this line will segfault ~50% of the time
timeit.timeit(stmt=stmt, setup=setup % 256, number = 1000)

[mattip]

fixed in pypy/pypy 5cfbc35539b9e9fc64ca960de325f36632a6cd83 . Turns out the root cause was a missing keepalive_until_here() gc hint, which through discussion became a context manager protecting access to array raw storage