[SciPy-dev] Memory error in interpolate.sproot

[Pauli Virtanen]

Mon, 10 Nov 2008 16:15:50 -0500, Nathan Bell wrote:

> On Mon, Nov 10, 2008 at 3:45 PM, Nils Wagner
> <nwagner@iam.uni-stuttgart.de> wrote:
>>
>> The same program works for me on my old 32bit laptop.
>>
>> Can somebody reproduce the problem on a 64-bit system ?
>>
>>
> Works for me.  I get a plot and the following output:
> 
> $ python -i test_iterpol.py
> Warning: the number of zeros exceeds mest

Valgrind spits out some warnings for me for the sproots line (Scipy r5054):

{{{
...
>>> y2 = splev(x2, tck)
>>> roots = sproot(tck, mest=2)
==4530== 
==4530== Conditional jump or move depends on uninitialised value(s)
==4530==    at 0x612DE8E: PyArray_NewFromDescr (arrayobject.c:5565)
==4530==    by 0xADF5316: fitpack_sproot (__fitpack.h:518)
==4530==    by 0x47F621: PyEval_EvalFrameEx (ceval.c:3566)
...
==4530== Conditional jump or move depends on uninitialised value(s)
==4530==    at 0x612DE90: PyArray_NewFromDescr (arrayobject.c:5566)
==4530==    by 0xADF5316: fitpack_sproot (__fitpack.h:518)
==4530==    by 0x47F621: PyEval_EvalFrameEx (ceval.c:3566)
...
...
...
==4530== Conditional jump or move depends on uninitialised value(s)
==4530==    at 0x4A1CFDA: memcpy (mc_replace_strmem.c:406)
==4530==    by 0xADF5337: fitpack_sproot (__fitpack.h:520)
==4530==    by 0x47F621: PyEval_EvalFrameEx (ceval.c:3566)
...
==4530== Conditional jump or move depends on uninitialised value(s)
==4530==    at 0x4A1CFF9: memcpy (mc_replace_strmem.c:406)
==4530==    by 0xADF5337: fitpack_sproot (__fitpack.h:520)
==4530==    by 0x47F621: PyEval_EvalFrameEx (ceval.c:3566)
...
...
...
==4530== Use of uninitialised value of size 8
==4530==    at 0x4A1D074: memcpy (mc_replace_strmem.c:406)
==4530==    by 0xADF5337: fitpack_sproot (__fitpack.h:520)
==4530==    by 0x47F621: PyEval_EvalFrameEx (ceval.c:3566)
...
...
Warning: the number of zeros exceeds mest
}}}

And... Bingo!

{{{
__fitpack.h:

    512   if ((z = (double *)malloc(mest*sizeof(double)))==NULL) {
    513     PyErr_NoMemory();
    514     goto fail;
    515   }
    516   SPROOT(t,&n,c,z,&mest,&m,&ier);
    517   if (ier==10) m=0;
    518   ap_z = (PyArrayObject *)PyArray_SimpleNew(1,&m,PyArray_DOUBLE);
    519   if (ap_z == NULL) goto fail;
    520   memcpy(ap_z->data,z,m*sizeof(double));
}}}

Obviously, the last line should be mest*sizeof(double). I'll fix this.

-- 
Pauli Virtanen