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Bug #1613

CRASH with RingHom from FrF

Added by John Abbott over 2 years ago. Updated over 2 years ago.

Status:
Closed
Priority:
High
Assignee:
Anna Maria Bigatti
Category:
Parser/Interpreter
Target version:
CoCoA-5.4.0
Start date:
30 Sep 2021
Due date:
% Done:

100%

Estimated time:
2.66 h
Spent time:
2.65 h

Description

The following causes a crash: why was the exception not caught and handled?

define FlattenRing(R)
  // Assume R = QQ(a)[x]
  nx := NumIndets(R);
  QQa := BaseRing(CoeffRing(R));
  na := NumIndets(QQa);
  FlatRing := NewPolyRing(CoeffRing(QQa), SymbolRange("x",1,na+nx));
  a_image := [indet(FlatRing, j) | j in 1..na];
  EmbedQQa := PolyAlgebraHom(QQa, FlatRing, a_image);
  phi := InducedHom(CoeffRing(R), EmbedQQa);
  x_image := [indet(FlatRing, na+j) | j in 1..nx];
  return PolyRingHom(R,FlatRing, phi, x_image);
enddefine; -- FlattenRing

/**/ QQa::=QQ[a];
/**/ FrFQQa := NewFractionField(QQa);
/**/ Px ::= FrFQQa[x,y];
/**/ FlattenRing(Px);
/**/ JJ := It;
/**/ use Px;
/**/ f := a*x^2-1/a;
/**/ JJ(f);

***ERROR***  UNCAUGHT CoCoA error

***************************************************************************
****CoCoA ERROR****  ErrCode: CoCoA::ERR::BadPartialRingHomArg
****CoCoA ERROR****  Message: Partial RingHom is undefined for this argument
****CoCoA ERROR****  Context: FractionFieldImpl::InducedHomImpl::myApply
****CoCoA ERROR****  File:    FractionField.C
****CoCoA ERROR****  Line:    789
***************************************************************************

Process cocoa5 exited abnormally with code 1

Related issues

Related to CoCoA-5 - Bug #1614: SourceRegion gives misleading error mesgClosed2021-10-02

History

#1 Updated by John Abbott over 2 years ago

Actually a separate bug: CommonDenom(a*x^2-1/a) gives 1 rather than a... Ooops!

NOTE the code looks fine, and now CommonDenom seems to work... not sure what the problem was. Ignoring.

#2 Updated by John Abbott over 2 years ago

  • Status changed from New to In Progress
  • % Done changed from 0 to 10

Simpler failing example:

Qa ::= QQ[a];
Qx ::= QQ[x];
phi:=PolyAlgebraHom(Qa,Qx,[indet(Qx,1)]);

F:=NewFractionField(Qa);
psi := InducedHom(F,phi);
use F;
psi(1/a);

Even simpler:

F3 ::= ZZ/(3);
phi := CanonicalHom(ZZ,F3);
psi := InducedHom(QQ,phi);
a:=psi(1/3);

Presumably the interpreter does not allow for "application" of a RingHom to fail... I wonder where that is in the source code (sigh)

#3 Updated by John Abbott over 2 years ago

Probable source code:
RINGHOM::eval around line 2792 in Interpreter.C

Probably called from: intrusive_ptr<Value> InvocationExpression::implEval(RuntimeEnvironment *runtimeEnv) const at line 3908

#4 Updated by John Abbott over 2 years ago

According to gdb the fn is called (indrectly) from Interpreter.C:3032 in Interpreter::run
I think the problem may lie here.
No time to investigate now.

NOTE perhaps the catch at line 3049 should be moved inside the block above???

#5 Updated by John Abbott over 2 years ago

  • Related to Bug #1614: SourceRegion gives misleading error mesg added

#6 Updated by Anna Maria Bigatti over 2 years ago

  • Project changed from CoCoALib to CoCoA-5
  • Category changed from Safety to Parser/Interpreter
  • Assignee set to Anna Maria Bigatti
  • Target version changed from CoCoALib-0.99800 to CoCoA-5.4.0

#7 Updated by John Abbott over 2 years ago

  • Status changed from In Progress to Resolved
  • % Done changed from 10 to 80

Similar to issue #1614, I have "hacked" the interpreter, and the examples seem to work now.
But I am not confident that the hack is sound and robust, so fear a future nasty jumping out on us at so point.

#8 Updated by John Abbott over 2 years ago

  • Status changed from Resolved to Closed
  • % Done changed from 80 to 100
  • Estimated time set to 2.66 h

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