[gecode-users] sorted constraint seg faults with empty arrays

[Kish Shen]

Hi,

I am getting a segmentation fault when using the sorted constraint with 
empty IntVarArgs arrays (i.e. size of the array is zero).

I found this when I was producing unit tests for the sorted constraint 
for the ECLiPSe Gecode interface. One of the thing I test for is for the 
variable array(s) being empty, because I expect the arguments to the 
constraints to be generated by the user's program, and it could be that 
this may result in no variables being involved in the constructed 
constraint. Originally I used to check if such arrays are empty, and 
raise an error at the ECLiPSe level if it is, so the Gecode constraint 
was never called with an empty array, but I was sent a program from one 
of our users who tried to call the lexicographical ordering constraints 
with empty arrays, and when I did pass the empty array to Gecode, it 
seem to cope without problems.

With the sorted constraint, I get a seg. fault. I am using

sort(home, x, y)

where both x and y are IntVarArgs of size 0, which should just succeed 
trivially, but it seems that the seg fault happens during the calling of 
sort().

This is the first constraint that I have run into problems with using 
size 0 IntVarArgs -- I have tested quite a few other constraints so far, 
and until now they have all worked.

I am using Gecode 3.7.1, and I tried on both 32 bit Linux and 64 bit 
Intel Mac.

Cheers,

Kish

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