I just stumbled upon some weird behavior in ifort 22.214.171.124 on CentOS 7. I am not entirely sure if this is a bug with the compiler or if it's non-standard Fortran so I wanted to ask here. Below is a MWE that illustrates the issue:
program test implicit none integer, allocatable :: a(:), b1(:), b2(:, :) b1 = [2, 1] b2 = reshape([1, -1, -2, -3, -4, 2, -5, -6, -7, -8], [5, 2]) a = b1(b2(1, :)) write(*, *) shape(a), "|", a end program test
What's important is that the output of this program depends on whether one uses runtime checks (-C) or not. Basically, we use b2(1,
2 | 2 1
However, after enabling runtime checks, the output changes to:
1 | 2
Is there something wrong with the code? I do believe all of this should be valid Fortran (2003).
I would say it is conforming. I can also confirm that the program works with Intel Fortran 2018, with and without -C (or -check:all). I get the same answer. gfortran also accepts it and produces the same output.
I traced the issue down to -check shape. It's embedded in -C.
Here's a workaround
+ ifort -C -check noshape c.f90 + a.out 2 | 2 1
I filed a bug on your behalf, CMPLRIL0-33624. I'll let you know when there's a fix.