#11551: Pari segfault on Sage startup in Cygwin
------------------------+---------------------------------------------------
Reporter: kcrisman | Owner: tbd
Type: defect | Status: new
Priority: major | Milestone: sage-4.7.2
Component: cygwin | Keywords: pari
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Comment(by kcrisman):
Replying to [comment:26 jdemeyer]:
> Replying to [comment:24 kcrisman]:
> > But here is something perhaps slightly more interesting. If I print
before and after
> > I get `bot=0` before, but `bot=212...` after, but `bot=0` again by the
time the program segfaults.
>
> `bot == 0` is certainly very bad and is surely the cause of the
segfault. It would be great if you could figure out why `bot` is set to
zero.
Hmm, okay. So here is what I discovered so far:
* The !PariInstance init is called well before the Pynac initialization.
* In the !PariInstance init, the actual deep copy is called three times,
and all is well.
* I am able to insert a statement like
{{{
print "bot is now", bot
}}}
in `real_mpfr.pyx`.
* I am '''not''' allowed to do this in other files where !PariInstance is
imported, such as `matrix/matrix_integer_dense.pyx`. On the very
reasonable grounds that
{{{
undeclared name not builtin:bot
}}}
Well! So why the heck is `real_mpfr.pyx` allowing me to insert this print
statement in the first place? It seems like this is why bot is causing
problems - it shouldn't even be defined. Nowhere else in that file is bot
used, other than in my print statements, as far as I could tell.
Anyway, in integer.pyx, Cython doesn't complain about this, and to my
surprise bot is already 0 there!
Let's look at the relevant order in sage/all.py:
{{{
<snip>
from sage.libs.all import * # here is where Pari gets imported, and
hence the PariInstance
from sage.rings.all import * # here is where integer.pyx presumably
is initialized and bot is already zero
from sage.matrix.all import *
# This must come before Calculus -- it initializes the Pynac library.
import sage.symbolic.pynac # here is where the symptom turned up while
initializing the square root of -1
}}}
I'll try to look into this a little more now, otherwise more tomorrow.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11551#comment:27>
Sage <http://www.sagemath.org>
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