Segfault for boolean evaluation of expression with assumptions

[sagetrac-tmonteil]

As reported on this ask question:

sage: x, y = var('x, y')
sage: assume(x>0)
sage: assume(y>0)
sage: bool(y*(x-y)==0)

leads to (on my computer 8.9.rc1) a sequence of:

;;;
;;; Detected access to protected memory, also kwown as 'bus or segmentation fault'.
;;; Jumping to the outermost toplevel prompt
;;;

followed by a Segmentation fault crash of Sage.

Or (as reported, on 8.8):

RuntimeError: ECL says: C-STACK overflow at size 1048576. Stack can probably be resized. Proceed with caution.

Exchanging x and y works correctly:

sage: x, y = var('x, y')
sage: assume(x>0)
sage: assume(y>0)
sage: bool(x*(y-x)==0)
False

Upstream ticket: https://sourceforge.net/p/maxima/bugs/3583/

Depends on #30063

Upstream: Fixed upstream, in a later stable release.

CC: @rwst @kcrisman

Component: symbolics

Author: Thierry Monteil

Branch/Commit: cb70171

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/28538

[EmmanuelCharpentier]

comment:1

On 8.9.rc1+#28534 (Python 3-based), I get a lot of

;;;
;;; Detected access to protected memory, also kwown as 'bus or segmentation fault'.
;;; Jumping to the outermost toplevel prompt
;;;

and a Sage crash:

Process Sage erreur de segmentation

Nice one...

[sagetrac-tmonteil]

Description changed:

--- 
+++ 
@@ -7,7 +7,7 @@
 sage: bool(y*(x-y)==0)
 ```
 
-leads to (on my computer 8.9.rc1):
+leads to (on my computer 8.9.rc1) a sequence of:
 
 ```
 ;;;
@@ -16,7 +16,9 @@
 ;;;
 ```
 
-or (as reported, on 8.8)
+followed by a `Segmentation fault` crash of Sage. 
+
+Or (as reported, on 8.8):
 
 ```
 RuntimeError: ECL says: C-STACK overflow at size 1048576. Stack can probably be resized. Proceed with caution.

[kcrisman]

comment:4

I'm so sorry I just don't have time any more to track down as many of these (though once in a while I somehow make the time). But I think the best thing to do is to do whatever bool does in Maxima-in-sage sage -maxima and then load exactly the packages preloaded by Sage - the complex domain is usually the most suspicious one on these fronts, though I have to say this is really puzzling. I imagine bool calls a comparison with zero at some point in Maxima, though I don't recall any more because I wasn't involved with the comparison-with-zero code much.

[nbruin]

comment:5

In maxima:

domain: complex;
assume(x>0,y>0);
is(equal(y*(x-y),0));

replicates the crash. That's sufficient to report upstream. Perhaps they can fix it.

[sagetrac-tmonteil]

Upstream: Reported upstream. No feedback yet.

[sagetrac-tmonteil]

comment:6

Thanks for tracking, this is now tracked upstream as https://sourceforge.net/p/maxima/bugs/3583/

[sagetrac-tmonteil]

Description changed:

--- 
+++ 
@@ -33,3 +33,5 @@
 sage: bool(x*(y-x)==0)
 False
 ```
+
+Upstream ticket: https://sourceforge.net/p/maxima/bugs/3583/

[sagetrac-tmonteil]

Changed upstream from Reported upstream. No feedback yet. to Fixed upstream, in a later stable release.

[embray]

comment:8

Ticket retargeted after milestone closed