[Bug-glpk] Bug in amd_order.c ?

[niels]

Hello,
    I'm sorry to say I think I may have found a small bug in amd_order.c

When using glpk 4.38 and I try to solve this problem with the interior 
point method (either null or default params) :

Minimize
  obj: - x_4 - x_5

Subject To
  r_1: + x_4 - 2 x_1 = 4
  r_2: + 2 x_5 + x_2 = 12
  r_3: + 2 x_5 + 3 x_4 + x_3 = 18

End

I get this:
glp_write_lp: writing problem data to `outpb.lp'...
Scaling...
  A: min|aij| =  1.000e+00  max|aij| =  3.000e+00  ratio =  3.000e+00
Problem data seem to be well scaled
GM: min|aij| =  8.882e-01  max|aij| =  1.126e+00  ratio =  1.268e+00
Original LP has 3 row(s), 5 column(s), and 7 non-zero(s)
Working LP has 3 row(s), 5 column(s), and 7 non-zero(s)
Matrix A has 7 non-zeros
Matrix S = A*A' has 5 non-zeros (upper triangle)
Approximate minimum degree ordering (AMD)...
xfree: ptr = (nil); null pointer
Error detected in file glplib07.c at line 175
Aborted


I traced through the code a bit and found that on line 132 in 
src/amd/amd_order.c you have:
        Rp = NULL ;

Then just before the status is returned (line 192 I think) you have
amd_free (Rp) ;

however since amd_free is a pseudonym of xfree and xfree throws the 
error above when it receives a var with an null value, you can see the 
problem...

Thanks and Regards,
    niels klitgord