https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97589
--- Comment #22 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Hi Toon,
it took some time, but we finally figured out that it is actually
a bug in your program that is causing problems.
It has (shortened)
nxglobal = 72;
This sets the coarray nxglobal to 72 on every image, including image 2.
if (this_image() == 1) then
read(*,config)
This optionally reads in nxglobal[1].
! Why won't this work as nxglobal[:] = nx ?
do i = 2, num_images()
nxglobal[i] = nxglobal;
This sets nxglobal[2] on image 2 from image 1. This is a race
condition: It is not clear which store comes first.
To fix this, you would need a "sync all" before the
if (this_image() = 1) statement, or you could set the default
value on image 1 only.
(Incidentally, looking at this code led to finding a bug in
namelist handling, where the implied this_image() was not honored
(namelist I/O only worked on image 1), so the time looking at this
bug was not wasted :-)
By the way, there is also a segfault with GFORTRAN_NUM_IMAGES=64, which
will need to be investigated.
