[Numpy-discussion] [ANN] numpy 1.4.0 rc2

Charles R Harris charlesr.harris@gmail....
Tue Dec 22 15:32:29 CST 2009


On Tue, Dec 22, 2009 at 12:40 PM, Pauli Virtanen <pav@iki.fi> wrote:

> ti, 2009-12-22 kello 10:16 -0700, Charles R Harris kirjoitti:
> [clip: PyOS_ascii_strtod -> PyOS_string_to_double]
> > The patch looks ok, but the functions handle errors differently and I
> > wonder if that has been completely audited.
>
> It can actually still crash from the same reason: PyOS_string_to_double
> docs say:
>
> """If no initial segment of the string is the valid representation of a
> floating-point number, set *endptr to point to the beginning of the
> string, raise ValueError, and return -1.0"""
>
> Indeed,
>
> $ gdb --args python3 -c "import numpy as np; np.fromstring('1,,', sep=',')"
> (gdb) run
> Program received signal SIGSEGV, Segmentation fault.
> PyErr_SetObject (exception=0x8291740, value=0xb7e926a0)
>    at ../Python/errors.c:67
> 67      ../Python/errors.c: Tiedostoa tai hakemistoa ei ole.
>        in ../Python/errors.c
> (gdb) bt
> #0  PyErr_SetObject (exception=0x8291740, value=0xb7e926a0)
>    at ../Python/errors.c:67
> #1  0x080e8d5a in PyErr_Format (exception=0x8291740,
>    format=0x81a0998 "could not convert string to float: %.200s")
>    at ../Python/errors.c:638
> #2  0x080fb5fe in PyOS_string_to_double (s=0xb7ca2ae2 ",",
> endptr=0xbfffd130,
>    overflow_exception=0x0) at ../Python/pystrtod.c:354
> #3  0x004a9bfc in NumPyOS_ascii_strtod (s=0xb7ca2ae2 ",",
> endptr=0xbfffd130)
>    at numpy/core/src/multiarray/numpyos.c:525
>
> I suppose raising an exception requires ownership of GIL. So either we
> implement ASCII number parsing ourselves from scratch (or steal it from
> somewhere), or surround the call with appropriate GIL-acquiring wrappers
> plus if (PyErr_Occurred()) PyErr_Clear();
>
>
Could you expand a bit on this? There are several places where
PyErr_Occurred are called and I am wondering if there is a problem. In fact,
I moved one such check and a segfault went away, which made me suspicious...

Chuck
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