https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97589
--- Comment #24 from Toon Moene <toon at moene dot org> --- And I can reproduce the GFORTRAN_NUM_IMAGES=64 segfault: (export LD_LIBRARY_PATH=/home/toon/compilers/install/coarray_native/lib/gcc/x86_64-pc-linux-gnu/11.0.0; export GFORTRAN_NUM_IMAGES=64; echo ' &config nxglobal=936, nyglobal=770, nzglobal=60 / ' | ./a.out) Program received signal SIGSEGV: Segmentation fault - invalid memory reference. Backtrace for this error: #0 0x7fec7b252bd0 in ??? #1 0x7fec7b251e25 in ??? #2 0x7fec7af00cbf in ??? #3 0x7fec7b5377ae in shared_malloc at /home/toon/compilers/coarray_native/libgfortran/caf_shared/allocator.c:70 #4 0x7fec7b5374ab in get_memory_by_id_internal at /home/toon/compilers/coarray_native/libgfortran/caf_shared/alloc.c:75 #5 0x4141ed in random_weather at /home/toon/src/random-weather.f90:551 #6 0x7fec7b537c0a in image_main_wrapper at /home/toon/compilers/coarray_native/libgfortran/caf_shared/coarraynative.c:183 #7 0x415d2a in main at /home/toon/src/random-weather.f90:413 ERROR: Image 64(0x3a877f) failed after which message it hangs ... Notably, I did add a check on boundary relaxation zone size, so that cannot be the problem.