Improve libGAP startup error handling

[vbraun]

Currently, libGAP doesn't give useful errors if something goes wrong during initialization.

Also, the GAP SIGINT handler got installed, this is fixed in the new spkg. Now Ctrl-C works as expected.

Install ​http://sagepad.org/spkg/libgap-4.5.6.p1.spkg

[vbraun]

Miguel, you said that you had some mysterious error. Can you try this patch? It depends on the recently-updated patches on #6391, #13211.

[mmarco]

I have been checking the different updates of libgap, and the error seemed to go away several versions ago. Anyways, i will keep testing it.

[mmarco]

I don't know if it is an issue related with this patch or if it comes from libgap itself, but i have experienced some problems when i use tab completion in a session in the command line (i haven't checked it in the notebook).

An example:

sage: F=libgap.eval('FreeGroup(2)')
sage: (a,b)=F.GeneratorsOfGroup()
sage: H=F/libgap([a^2,b^2,a*b*a*b])
sage: H
<fp group on the generators [ f1, f2 ]>
sage: H.IsomorphismSimplifiedFpGroup()
[ f1, f2 ] -> [ f1, f2 ]
sage: H=F/libgap([a^2,b^2,a*b])    
sage: c=H.Gene
H.GeneralLinearGroup      H.GeneralisedEigenspaces  H.GeneralizedEigenvalues  H.GeneratorsOfIdeal
H.GeneralOrthogonalGroup  H.GeneralisedEigenvalues  H.GeneratorsOfField       
H.GeneralUnitaryGroup     H.GeneralizedEigenspaces  H.GeneratorsOfGroup       
sage: c=H.GeneratorsOfGroup()[0]
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)

/home/mmarco/sage-5.4/<ipython console> in <module>()

/home/mmarco/sage-5.4/local/lib/python2.7/site-packages/sage/libs/gap/element.so in sage.libs.gap.element.GapElement.__getattr__ (sage/libs/gap/element.c:3555)()

AttributeError: Name "GeneratorsOfGroup" is not defined in GAP.
sage: c=H.GeneratorsOfGroup()   
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)

/home/mmarco/sage-5.4/<ipython console> in <module>()

/home/mmarco/sage-5.4/local/lib/python2.7/site-packages/sage/libs/gap/element.so in sage.libs.gap.element.GapElement.__getattr__ (sage/libs/gap/element.c:3555)()

AttributeError: Name "GeneratorsOfGroup" is not defined in GAP.
sage: H
Exception RuntimeError: 'Entered a critical block twice' in 'sage.libs.gap.util.error_handler' ignored
<fp group on the generators [ f1, f2 ]>
sage: H.GeneratorsOfGroup()
[ f1, f2 ]
sage: c=H.GeneratorsOfGroup()[0]
sage: c
f1
sage: c=H.Generat
H.GeneratorsOfField  H.GeneratorsOfGroup  H.GeneratorsOfIdeal  
sage: c=H.GeneratorsOfGroup()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)

/home/mmarco/sage-5.4/<ipython console> in <module>()

/home/mmarco/sage-5.4/local/lib/python2.7/site-packages/sage/libs/gap/element.so in sage.libs.gap.element.GapElement.__getattr__ (sage/libs/gap/element.c:3555)()

AttributeError: Name "GeneratorsOfGroup" is not defined in GAP.
sage: c=H.GeneratorsOfGroup()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)

/home/mmarco/sage-5.4/<ipython console> in <module>()

/home/mmarco/sage-5.4/local/lib/python2.7/site-packages/sage/libs/gap/element.so in sage.libs.gap.element.GapElement.__getattr__ (sage/libs/gap/element.c:3555)()

AttributeError: Name "GeneratorsOfGroup" is not defined in GAP.
sage: H
Exception RuntimeError: 'Entered a critical block twice' in 'sage.libs.gap.util.error_handler' ignored
<fp group on the generators [ f1, f2 ]>
sage: c=H.GeneratorsOfGroup()

[mmarco]

This same behaviour appears when i don't use this patch, so reported in the libgap ticket.

[vbraun]

Updated patch fixes the issue with the command line completion

[vbraun]

Updated spkg fixes long input lines (>32k characters):

sage: S = SymmetricGroup(10000)
sage: s = S.random_element()
sage: len(str(s._gap_()))
61673
sage: libgap(s)
(1,5243,8582,5012,6862,7477,1681,7423,8405,3101,...,5257,9362,2495,8500)( [...] )